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John Criswellbd9d3702005-10-27 16:00:10 +00001//===-- ConstantFolding.cpp - Analyze constant folding possibilities ------===//
2//
3// The LLVM Compiler Infrastructure
4//
Chris Lattner4ee451d2007-12-29 20:36:04 +00005// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
John Criswellbd9d3702005-10-27 16:00:10 +00007//
8//===----------------------------------------------------------------------===//
9//
10// This family of functions determines the possibility of performing constant
11// folding.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Analysis/ConstantFolding.h"
16#include "llvm/Constants.h"
17#include "llvm/DerivedTypes.h"
Chris Lattner55207322007-01-30 23:45:45 +000018#include "llvm/Function.h"
John Criswellbd9d3702005-10-27 16:00:10 +000019#include "llvm/Instructions.h"
20#include "llvm/Intrinsics.h"
Chris Lattner55207322007-01-30 23:45:45 +000021#include "llvm/ADT/SmallVector.h"
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +000022#include "llvm/ADT/StringMap.h"
Chris Lattner03dd25c2007-01-31 00:51:48 +000023#include "llvm/Target/TargetData.h"
John Criswellbd9d3702005-10-27 16:00:10 +000024#include "llvm/Support/GetElementPtrTypeIterator.h"
25#include "llvm/Support/MathExtras.h"
26#include <cerrno>
Jeff Cohen97af7512006-12-02 02:22:01 +000027#include <cmath>
John Criswellbd9d3702005-10-27 16:00:10 +000028using namespace llvm;
29
Chris Lattner03dd25c2007-01-31 00:51:48 +000030//===----------------------------------------------------------------------===//
31// Constant Folding internal helper functions
32//===----------------------------------------------------------------------===//
33
34/// IsConstantOffsetFromGlobal - If this constant is actually a constant offset
35/// from a global, return the global and the constant. Because of
36/// constantexprs, this function is recursive.
37static bool IsConstantOffsetFromGlobal(Constant *C, GlobalValue *&GV,
38 int64_t &Offset, const TargetData &TD) {
39 // Trivial case, constant is the global.
40 if ((GV = dyn_cast<GlobalValue>(C))) {
41 Offset = 0;
42 return true;
43 }
44
45 // Otherwise, if this isn't a constant expr, bail out.
46 ConstantExpr *CE = dyn_cast<ConstantExpr>(C);
47 if (!CE) return false;
48
49 // Look through ptr->int and ptr->ptr casts.
50 if (CE->getOpcode() == Instruction::PtrToInt ||
51 CE->getOpcode() == Instruction::BitCast)
52 return IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD);
53
54 // i32* getelementptr ([5 x i32]* @a, i32 0, i32 5)
55 if (CE->getOpcode() == Instruction::GetElementPtr) {
56 // Cannot compute this if the element type of the pointer is missing size
57 // info.
Chris Lattnerf286f6f2007-12-10 22:53:04 +000058 if (!cast<PointerType>(CE->getOperand(0)->getType())
59 ->getElementType()->isSized())
Chris Lattner03dd25c2007-01-31 00:51:48 +000060 return false;
61
62 // If the base isn't a global+constant, we aren't either.
63 if (!IsConstantOffsetFromGlobal(CE->getOperand(0), GV, Offset, TD))
64 return false;
65
66 // Otherwise, add any offset that our operands provide.
67 gep_type_iterator GTI = gep_type_begin(CE);
Gabor Greifde2d74b2008-05-22 06:43:33 +000068 for (User::const_op_iterator i = CE->op_begin() + 1, e = CE->op_end();
Gabor Greif785c6af2008-05-22 19:24:54 +000069 i != e; ++i, ++GTI) {
Gabor Greifde2d74b2008-05-22 06:43:33 +000070 ConstantInt *CI = dyn_cast<ConstantInt>(*i);
Chris Lattner03dd25c2007-01-31 00:51:48 +000071 if (!CI) return false; // Index isn't a simple constant?
72 if (CI->getZExtValue() == 0) continue; // Not adding anything.
73
74 if (const StructType *ST = dyn_cast<StructType>(*GTI)) {
75 // N = N + Offset
Chris Lattnerb1919e22007-02-10 19:55:17 +000076 Offset += TD.getStructLayout(ST)->getElementOffset(CI->getZExtValue());
Chris Lattner03dd25c2007-01-31 00:51:48 +000077 } else {
Jeff Cohenca5183d2007-03-05 00:00:42 +000078 const SequentialType *SQT = cast<SequentialType>(*GTI);
Duncan Sands514ab342007-11-01 20:53:16 +000079 Offset += TD.getABITypeSize(SQT->getElementType())*CI->getSExtValue();
Chris Lattner03dd25c2007-01-31 00:51:48 +000080 }
81 }
82 return true;
83 }
84
85 return false;
86}
87
88
89/// SymbolicallyEvaluateBinop - One of Op0/Op1 is a constant expression.
90/// Attempt to symbolically evaluate the result of a binary operator merging
91/// these together. If target data info is available, it is provided as TD,
92/// otherwise TD is null.
93static Constant *SymbolicallyEvaluateBinop(unsigned Opc, Constant *Op0,
94 Constant *Op1, const TargetData *TD){
95 // SROA
96
97 // Fold (and 0xffffffff00000000, (shl x, 32)) -> shl.
98 // Fold (lshr (or X, Y), 32) -> (lshr [X/Y], 32) if one doesn't contribute
99 // bits.
100
101
102 // If the constant expr is something like &A[123] - &A[4].f, fold this into a
103 // constant. This happens frequently when iterating over a global array.
104 if (Opc == Instruction::Sub && TD) {
105 GlobalValue *GV1, *GV2;
106 int64_t Offs1, Offs2;
107
108 if (IsConstantOffsetFromGlobal(Op0, GV1, Offs1, *TD))
109 if (IsConstantOffsetFromGlobal(Op1, GV2, Offs2, *TD) &&
110 GV1 == GV2) {
111 // (&GV+C1) - (&GV+C2) -> C1-C2, pointer arithmetic cannot overflow.
112 return ConstantInt::get(Op0->getType(), Offs1-Offs2);
113 }
114 }
115
116 // TODO: Fold icmp setne/seteq as well.
117 return 0;
118}
119
120/// SymbolicallyEvaluateGEP - If we can symbolically evaluate the specified GEP
121/// constant expression, do so.
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000122static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
Chris Lattner03dd25c2007-01-31 00:51:48 +0000123 const Type *ResultTy,
124 const TargetData *TD) {
125 Constant *Ptr = Ops[0];
Chris Lattner268e7d72008-05-08 04:54:43 +0000126 if (!TD || !cast<PointerType>(Ptr->getType())->getElementType()->isSized())
Chris Lattner03dd25c2007-01-31 00:51:48 +0000127 return 0;
128
Chris Lattner268e7d72008-05-08 04:54:43 +0000129 uint64_t BasePtr = 0;
130 if (!Ptr->isNullValue()) {
131 // If this is a inttoptr from a constant int, we can fold this as the base,
132 // otherwise we can't.
133 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
134 if (CE->getOpcode() == Instruction::IntToPtr)
135 if (ConstantInt *Base = dyn_cast<ConstantInt>(CE->getOperand(0)))
136 BasePtr = Base->getZExtValue();
137
138 if (BasePtr == 0)
139 return 0;
Chris Lattner03dd25c2007-01-31 00:51:48 +0000140 }
Chris Lattner268e7d72008-05-08 04:54:43 +0000141
142 // If this is a constant expr gep that is effectively computing an
143 // "offsetof", fold it into 'cast int Size to T*' instead of 'gep 0, 0, 12'
144 for (unsigned i = 1; i != NumOps; ++i)
145 if (!isa<ConstantInt>(Ops[i]))
146 return false;
147
148 uint64_t Offset = TD->getIndexedOffset(Ptr->getType(),
149 (Value**)Ops+1, NumOps-1);
150 Constant *C = ConstantInt::get(TD->getIntPtrType(), Offset+BasePtr);
151 return ConstantExpr::getIntToPtr(C, ResultTy);
Chris Lattner03dd25c2007-01-31 00:51:48 +0000152}
153
Chris Lattner1afab9c2007-12-11 07:29:44 +0000154/// FoldBitCast - Constant fold bitcast, symbolically evaluating it with
155/// targetdata. Return 0 if unfoldable.
156static Constant *FoldBitCast(Constant *C, const Type *DestTy,
157 const TargetData &TD) {
158 // If this is a bitcast from constant vector -> vector, fold it.
159 if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
160 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) {
161 // If the element types match, VMCore can fold it.
162 unsigned NumDstElt = DestVTy->getNumElements();
163 unsigned NumSrcElt = CV->getNumOperands();
164 if (NumDstElt == NumSrcElt)
165 return 0;
166
167 const Type *SrcEltTy = CV->getType()->getElementType();
168 const Type *DstEltTy = DestVTy->getElementType();
169
170 // Otherwise, we're changing the number of elements in a vector, which
171 // requires endianness information to do the right thing. For example,
172 // bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
173 // folds to (little endian):
174 // <4 x i32> <i32 0, i32 0, i32 1, i32 0>
175 // and to (big endian):
176 // <4 x i32> <i32 0, i32 0, i32 0, i32 1>
177
178 // First thing is first. We only want to think about integer here, so if
179 // we have something in FP form, recast it as integer.
180 if (DstEltTy->isFloatingPoint()) {
181 // Fold to an vector of integers with same size as our FP type.
182 unsigned FPWidth = DstEltTy->getPrimitiveSizeInBits();
183 const Type *DestIVTy = VectorType::get(IntegerType::get(FPWidth),
184 NumDstElt);
185 // Recursively handle this integer conversion, if possible.
186 C = FoldBitCast(C, DestIVTy, TD);
187 if (!C) return 0;
188
189 // Finally, VMCore can handle this now that #elts line up.
190 return ConstantExpr::getBitCast(C, DestTy);
191 }
192
193 // Okay, we know the destination is integer, if the input is FP, convert
194 // it to integer first.
195 if (SrcEltTy->isFloatingPoint()) {
196 unsigned FPWidth = SrcEltTy->getPrimitiveSizeInBits();
197 const Type *SrcIVTy = VectorType::get(IntegerType::get(FPWidth),
198 NumSrcElt);
199 // Ask VMCore to do the conversion now that #elts line up.
200 C = ConstantExpr::getBitCast(C, SrcIVTy);
201 CV = dyn_cast<ConstantVector>(C);
202 if (!CV) return 0; // If VMCore wasn't able to fold it, bail out.
203 }
204
205 // Now we know that the input and output vectors are both integer vectors
206 // of the same size, and that their #elements is not the same. Do the
207 // conversion here, which depends on whether the input or output has
208 // more elements.
209 bool isLittleEndian = TD.isLittleEndian();
210
211 SmallVector<Constant*, 32> Result;
212 if (NumDstElt < NumSrcElt) {
213 // Handle: bitcast (<4 x i32> <i32 0, i32 1, i32 2, i32 3> to <2 x i64>)
214 Constant *Zero = Constant::getNullValue(DstEltTy);
215 unsigned Ratio = NumSrcElt/NumDstElt;
216 unsigned SrcBitSize = SrcEltTy->getPrimitiveSizeInBits();
217 unsigned SrcElt = 0;
218 for (unsigned i = 0; i != NumDstElt; ++i) {
219 // Build each element of the result.
220 Constant *Elt = Zero;
221 unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
222 for (unsigned j = 0; j != Ratio; ++j) {
223 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(SrcElt++));
224 if (!Src) return 0; // Reject constantexpr elements.
225
226 // Zero extend the element to the right size.
227 Src = ConstantExpr::getZExt(Src, Elt->getType());
228
229 // Shift it to the right place, depending on endianness.
230 Src = ConstantExpr::getShl(Src,
231 ConstantInt::get(Src->getType(), ShiftAmt));
232 ShiftAmt += isLittleEndian ? SrcBitSize : -SrcBitSize;
233
234 // Mix it in.
235 Elt = ConstantExpr::getOr(Elt, Src);
236 }
237 Result.push_back(Elt);
238 }
239 } else {
240 // Handle: bitcast (<2 x i64> <i64 0, i64 1> to <4 x i32>)
241 unsigned Ratio = NumDstElt/NumSrcElt;
242 unsigned DstBitSize = DstEltTy->getPrimitiveSizeInBits();
243
244 // Loop over each source value, expanding into multiple results.
245 for (unsigned i = 0; i != NumSrcElt; ++i) {
246 Constant *Src = dyn_cast<ConstantInt>(CV->getOperand(i));
247 if (!Src) return 0; // Reject constantexpr elements.
248
249 unsigned ShiftAmt = isLittleEndian ? 0 : DstBitSize*(Ratio-1);
250 for (unsigned j = 0; j != Ratio; ++j) {
251 // Shift the piece of the value into the right place, depending on
252 // endianness.
253 Constant *Elt = ConstantExpr::getLShr(Src,
254 ConstantInt::get(Src->getType(), ShiftAmt));
255 ShiftAmt += isLittleEndian ? DstBitSize : -DstBitSize;
256
257 // Truncate and remember this piece.
258 Result.push_back(ConstantExpr::getTrunc(Elt, DstEltTy));
259 }
260 }
261 }
262
263 return ConstantVector::get(&Result[0], Result.size());
264 }
265 }
266
267 return 0;
268}
269
Chris Lattner03dd25c2007-01-31 00:51:48 +0000270
271//===----------------------------------------------------------------------===//
272// Constant Folding public APIs
273//===----------------------------------------------------------------------===//
274
275
Chris Lattner55207322007-01-30 23:45:45 +0000276/// ConstantFoldInstruction - Attempt to constant fold the specified
277/// instruction. If successful, the constant result is returned, if not, null
278/// is returned. Note that this function can only fail when attempting to fold
279/// instructions like loads and stores, which have no constant expression form.
280///
281Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
282 if (PHINode *PN = dyn_cast<PHINode>(I)) {
283 if (PN->getNumIncomingValues() == 0)
284 return Constant::getNullValue(PN->getType());
John Criswellbd9d3702005-10-27 16:00:10 +0000285
Chris Lattner55207322007-01-30 23:45:45 +0000286 Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
287 if (Result == 0) return 0;
288
289 // Handle PHI nodes specially here...
290 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i)
291 if (PN->getIncomingValue(i) != Result && PN->getIncomingValue(i) != PN)
292 return 0; // Not all the same incoming constants...
293
294 // If we reach here, all incoming values are the same constant.
295 return Result;
296 }
297
298 // Scan the operand list, checking to see if they are all constants, if so,
299 // hand off to ConstantFoldInstOperands.
300 SmallVector<Constant*, 8> Ops;
Gabor Greifde2d74b2008-05-22 06:43:33 +0000301 for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
302 if (Constant *Op = dyn_cast<Constant>(*i))
Chris Lattner55207322007-01-30 23:45:45 +0000303 Ops.push_back(Op);
304 else
305 return 0; // All operands not constant!
306
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000307 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
308 return ConstantFoldCompareInstOperands(CI->getPredicate(),
309 &Ops[0], Ops.size(), TD);
310 else
311 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
312 &Ops[0], Ops.size(), TD);
Chris Lattner55207322007-01-30 23:45:45 +0000313}
314
Nick Lewycky3dfd7bf2008-05-25 20:56:15 +0000315/// ConstantFoldConstantExpression - Attempt to fold the constant expression
316/// using the specified TargetData. If successful, the constant result is
317/// result is returned, if not, null is returned.
318Constant *llvm::ConstantFoldConstantExpression(ConstantExpr *CE,
319 const TargetData *TD) {
320 assert(TD && "ConstantFoldConstantExpression requires a valid TargetData.");
321
322 SmallVector<Constant*, 8> Ops;
323 for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
324 Ops.push_back(cast<Constant>(*i));
325
326 if (CE->isCompare())
327 return ConstantFoldCompareInstOperands(CE->getPredicate(),
328 &Ops[0], Ops.size(), TD);
329 else
330 return ConstantFoldInstOperands(CE->getOpcode(), CE->getType(),
331 &Ops[0], Ops.size(), TD);
332}
333
Chris Lattner55207322007-01-30 23:45:45 +0000334/// ConstantFoldInstOperands - Attempt to constant fold an instruction with the
335/// specified opcode and operands. If successful, the constant result is
336/// returned, if not, null is returned. Note that this function can fail when
337/// attempting to fold instructions like loads and stores, which have no
338/// constant expression form.
339///
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000340Constant *llvm::ConstantFoldInstOperands(unsigned Opcode, const Type *DestTy,
341 Constant* const* Ops, unsigned NumOps,
Chris Lattner55207322007-01-30 23:45:45 +0000342 const TargetData *TD) {
Chris Lattner03dd25c2007-01-31 00:51:48 +0000343 // Handle easy binops first.
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000344 if (Instruction::isBinaryOp(Opcode)) {
Chris Lattner03dd25c2007-01-31 00:51:48 +0000345 if (isa<ConstantExpr>(Ops[0]) || isa<ConstantExpr>(Ops[1]))
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000346 if (Constant *C = SymbolicallyEvaluateBinop(Opcode, Ops[0], Ops[1], TD))
Chris Lattner03dd25c2007-01-31 00:51:48 +0000347 return C;
348
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000349 return ConstantExpr::get(Opcode, Ops[0], Ops[1]);
Chris Lattner03dd25c2007-01-31 00:51:48 +0000350 }
Chris Lattner55207322007-01-30 23:45:45 +0000351
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000352 switch (Opcode) {
Chris Lattner55207322007-01-30 23:45:45 +0000353 default: return 0;
354 case Instruction::Call:
355 if (Function *F = dyn_cast<Function>(Ops[0]))
356 if (canConstantFoldCallTo(F))
Chris Lattnerad58eb32007-01-31 18:04:55 +0000357 return ConstantFoldCall(F, Ops+1, NumOps-1);
Chris Lattner55207322007-01-30 23:45:45 +0000358 return 0;
359 case Instruction::ICmp:
360 case Instruction::FCmp:
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000361 assert(0 &&"This function is invalid for compares: no predicate specified");
Chris Lattner001f7532007-08-11 23:49:01 +0000362 case Instruction::PtrToInt:
363 // If the input is a inttoptr, eliminate the pair. This requires knowing
364 // the width of a pointer, so it can't be done in ConstantExpr::getCast.
365 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0])) {
366 if (TD && CE->getOpcode() == Instruction::IntToPtr) {
367 Constant *Input = CE->getOperand(0);
368 unsigned InWidth = Input->getType()->getPrimitiveSizeInBits();
369 Constant *Mask =
370 ConstantInt::get(APInt::getLowBitsSet(InWidth,
371 TD->getPointerSizeInBits()));
372 Input = ConstantExpr::getAnd(Input, Mask);
373 // Do a zext or trunc to get to the dest size.
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000374 return ConstantExpr::getIntegerCast(Input, DestTy, false);
Chris Lattner001f7532007-08-11 23:49:01 +0000375 }
376 }
Chris Lattner1afab9c2007-12-11 07:29:44 +0000377 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
Chris Lattner001f7532007-08-11 23:49:01 +0000378 case Instruction::IntToPtr:
Chris Lattner55207322007-01-30 23:45:45 +0000379 case Instruction::Trunc:
380 case Instruction::ZExt:
381 case Instruction::SExt:
382 case Instruction::FPTrunc:
383 case Instruction::FPExt:
384 case Instruction::UIToFP:
385 case Instruction::SIToFP:
386 case Instruction::FPToUI:
387 case Instruction::FPToSI:
Chris Lattner1afab9c2007-12-11 07:29:44 +0000388 return ConstantExpr::getCast(Opcode, Ops[0], DestTy);
Chris Lattner55207322007-01-30 23:45:45 +0000389 case Instruction::BitCast:
Chris Lattner1afab9c2007-12-11 07:29:44 +0000390 if (TD)
391 if (Constant *C = FoldBitCast(Ops[0], DestTy, *TD))
392 return C;
393 return ConstantExpr::getBitCast(Ops[0], DestTy);
Chris Lattner55207322007-01-30 23:45:45 +0000394 case Instruction::Select:
395 return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2]);
396 case Instruction::ExtractElement:
397 return ConstantExpr::getExtractElement(Ops[0], Ops[1]);
398 case Instruction::InsertElement:
399 return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2]);
400 case Instruction::ShuffleVector:
401 return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2]);
402 case Instruction::GetElementPtr:
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000403 if (Constant *C = SymbolicallyEvaluateGEP(Ops, NumOps, DestTy, TD))
Chris Lattner03dd25c2007-01-31 00:51:48 +0000404 return C;
405
Chris Lattnerd917fe52007-01-31 04:42:05 +0000406 return ConstantExpr::getGetElementPtr(Ops[0], Ops+1, NumOps-1);
Chris Lattner55207322007-01-30 23:45:45 +0000407 }
408}
409
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000410/// ConstantFoldCompareInstOperands - Attempt to constant fold a compare
411/// instruction (icmp/fcmp) with the specified operands. If it fails, it
412/// returns a constant expression of the specified operands.
413///
414Constant *llvm::ConstantFoldCompareInstOperands(unsigned Predicate,
415 Constant*const * Ops,
416 unsigned NumOps,
417 const TargetData *TD) {
418 // fold: icmp (inttoptr x), null -> icmp x, 0
419 // fold: icmp (ptrtoint x), 0 -> icmp x, null
Nick Lewycky3dfd7bf2008-05-25 20:56:15 +0000420 // fold: icmp (inttoptr x), (inttoptr y) -> icmp trunc/zext x, trunc/zext y
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000421 // fold: icmp (ptrtoint x), (ptrtoint y) -> icmp x, y
422 //
423 // ConstantExpr::getCompare cannot do this, because it doesn't have TD
424 // around to know if bit truncation is happening.
425 if (ConstantExpr *CE0 = dyn_cast<ConstantExpr>(Ops[0])) {
426 if (TD && Ops[1]->isNullValue()) {
427 const Type *IntPtrTy = TD->getIntPtrType();
428 if (CE0->getOpcode() == Instruction::IntToPtr) {
429 // Convert the integer value to the right size to ensure we get the
430 // proper extension or truncation.
431 Constant *C = ConstantExpr::getIntegerCast(CE0->getOperand(0),
432 IntPtrTy, false);
433 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
434 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
435 }
436
437 // Only do this transformation if the int is intptrty in size, otherwise
438 // there is a truncation or extension that we aren't modeling.
439 if (CE0->getOpcode() == Instruction::PtrToInt &&
440 CE0->getType() == IntPtrTy) {
441 Constant *C = CE0->getOperand(0);
442 Constant *NewOps[] = { C, Constant::getNullValue(C->getType()) };
443 // FIXME!
444 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
445 }
446 }
447
Nick Lewycky3dfd7bf2008-05-25 20:56:15 +0000448 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(Ops[1])) {
449 if (TD && CE0->getOpcode() == CE1->getOpcode()) {
450 const Type *IntPtrTy = TD->getIntPtrType();
451
452 if (CE0->getOpcode() == Instruction::IntToPtr) {
453 // Convert the integer value to the right size to ensure we get the
454 // proper extension or truncation.
455 Constant *C0 = ConstantExpr::getIntegerCast(CE0->getOperand(0),
456 IntPtrTy, false);
457 Constant *C1 = ConstantExpr::getIntegerCast(CE1->getOperand(0),
458 IntPtrTy, false);
459 Constant *NewOps[] = { C0, C1 };
460 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
461 }
462
463 // Only do this transformation if the int is intptrty in size, otherwise
464 // there is a truncation or extension that we aren't modeling.
465 if ((CE0->getOpcode() == Instruction::PtrToInt &&
466 CE0->getType() == IntPtrTy &&
467 CE0->getOperand(0)->getType() == CE1->getOperand(0)->getType())) {
468 Constant *NewOps[] = {
469 CE0->getOperand(0), CE1->getOperand(0)
470 };
471 return ConstantFoldCompareInstOperands(Predicate, NewOps, 2, TD);
472 }
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000473 }
474 }
475 }
476 return ConstantExpr::getCompare(Predicate, Ops[0], Ops[1]);
477}
478
479
Chris Lattner55207322007-01-30 23:45:45 +0000480/// ConstantFoldLoadThroughGEPConstantExpr - Given a constant and a
481/// getelementptr constantexpr, return the constant value being addressed by the
482/// constant expression, or null if something is funny and we can't decide.
483Constant *llvm::ConstantFoldLoadThroughGEPConstantExpr(Constant *C,
484 ConstantExpr *CE) {
485 if (CE->getOperand(1) != Constant::getNullValue(CE->getOperand(1)->getType()))
486 return 0; // Do not allow stepping over the value!
487
488 // Loop over all of the operands, tracking down which value we are
489 // addressing...
490 gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE);
491 for (++I; I != E; ++I)
492 if (const StructType *STy = dyn_cast<StructType>(*I)) {
493 ConstantInt *CU = cast<ConstantInt>(I.getOperand());
494 assert(CU->getZExtValue() < STy->getNumElements() &&
495 "Struct index out of range!");
496 unsigned El = (unsigned)CU->getZExtValue();
497 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
498 C = CS->getOperand(El);
499 } else if (isa<ConstantAggregateZero>(C)) {
500 C = Constant::getNullValue(STy->getElementType(El));
501 } else if (isa<UndefValue>(C)) {
502 C = UndefValue::get(STy->getElementType(El));
503 } else {
504 return 0;
505 }
506 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(I.getOperand())) {
507 if (const ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
508 if (CI->getZExtValue() >= ATy->getNumElements())
509 return 0;
510 if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
511 C = CA->getOperand(CI->getZExtValue());
512 else if (isa<ConstantAggregateZero>(C))
513 C = Constant::getNullValue(ATy->getElementType());
514 else if (isa<UndefValue>(C))
515 C = UndefValue::get(ATy->getElementType());
516 else
517 return 0;
Reid Spencer9d6565a2007-02-15 02:26:10 +0000518 } else if (const VectorType *PTy = dyn_cast<VectorType>(*I)) {
Chris Lattner55207322007-01-30 23:45:45 +0000519 if (CI->getZExtValue() >= PTy->getNumElements())
520 return 0;
Reid Spencer9d6565a2007-02-15 02:26:10 +0000521 if (ConstantVector *CP = dyn_cast<ConstantVector>(C))
Chris Lattner55207322007-01-30 23:45:45 +0000522 C = CP->getOperand(CI->getZExtValue());
523 else if (isa<ConstantAggregateZero>(C))
524 C = Constant::getNullValue(PTy->getElementType());
525 else if (isa<UndefValue>(C))
526 C = UndefValue::get(PTy->getElementType());
527 else
528 return 0;
529 } else {
530 return 0;
531 }
532 } else {
533 return 0;
534 }
535 return C;
536}
537
538
539//===----------------------------------------------------------------------===//
540// Constant Folding for Calls
541//
John Criswellbd9d3702005-10-27 16:00:10 +0000542
543/// canConstantFoldCallTo - Return true if its even possible to fold a call to
544/// the specified function.
545bool
Dan Gohmanfa9b80e2008-01-31 01:05:10 +0000546llvm::canConstantFoldCallTo(const Function *F) {
John Criswellbd9d3702005-10-27 16:00:10 +0000547 switch (F->getIntrinsicID()) {
Dale Johannesen9ab7fb32007-10-02 17:43:59 +0000548 case Intrinsic::sqrt:
549 case Intrinsic::powi:
Reid Spencere9391fd2007-04-01 07:35:23 +0000550 case Intrinsic::bswap:
551 case Intrinsic::ctpop:
552 case Intrinsic::ctlz:
553 case Intrinsic::cttz:
John Criswellbd9d3702005-10-27 16:00:10 +0000554 return true;
555 default: break;
556 }
557
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000558 const ValueName *NameVal = F->getValueName();
Chris Lattnera099b6c2007-08-08 16:07:23 +0000559 if (NameVal == 0) return false;
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000560 const char *Str = NameVal->getKeyData();
561 unsigned Len = NameVal->getKeyLength();
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000562
563 // In these cases, the check of the length is required. We don't want to
564 // return true for a name like "cos\0blah" which strcmp would return equal to
565 // "cos", but has length 8.
566 switch (Str[0]) {
567 default: return false;
568 case 'a':
569 if (Len == 4)
570 return !strcmp(Str, "acos") || !strcmp(Str, "asin") ||
571 !strcmp(Str, "atan");
572 else if (Len == 5)
573 return !strcmp(Str, "atan2");
574 return false;
575 case 'c':
576 if (Len == 3)
577 return !strcmp(Str, "cos");
578 else if (Len == 4)
579 return !strcmp(Str, "ceil") || !strcmp(Str, "cosf") ||
580 !strcmp(Str, "cosh");
581 return false;
582 case 'e':
583 if (Len == 3)
584 return !strcmp(Str, "exp");
585 return false;
586 case 'f':
587 if (Len == 4)
588 return !strcmp(Str, "fabs") || !strcmp(Str, "fmod");
589 else if (Len == 5)
590 return !strcmp(Str, "floor");
591 return false;
592 break;
593 case 'l':
594 if (Len == 3 && !strcmp(Str, "log"))
595 return true;
596 if (Len == 5 && !strcmp(Str, "log10"))
597 return true;
598 return false;
599 case 'p':
600 if (Len == 3 && !strcmp(Str, "pow"))
601 return true;
602 return false;
603 case 's':
604 if (Len == 3)
605 return !strcmp(Str, "sin");
606 if (Len == 4)
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000607 return !strcmp(Str, "sinh") || !strcmp(Str, "sqrt") ||
608 !strcmp(Str, "sinf");
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000609 if (Len == 5)
610 return !strcmp(Str, "sqrtf");
611 return false;
612 case 't':
613 if (Len == 3 && !strcmp(Str, "tan"))
614 return true;
615 else if (Len == 4 && !strcmp(Str, "tanh"))
616 return true;
617 return false;
John Criswellbd9d3702005-10-27 16:00:10 +0000618 }
619}
620
Chris Lattner72d88ae2007-01-30 23:15:43 +0000621static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
622 const Type *Ty) {
John Criswellbd9d3702005-10-27 16:00:10 +0000623 errno = 0;
624 V = NativeFP(V);
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000625 if (errno != 0) {
626 errno = 0;
627 return 0;
Dale Johannesen43421b32007-09-06 18:13:44 +0000628 }
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000629
630 if (Ty == Type::FloatTy)
Chris Lattner02a260a2008-04-20 00:41:09 +0000631 return ConstantFP::get(APFloat((float)V));
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000632 if (Ty == Type::DoubleTy)
Chris Lattner02a260a2008-04-20 00:41:09 +0000633 return ConstantFP::get(APFloat(V));
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000634 assert(0 && "Can only constant fold float/double");
Gabor Greif33e456d2008-05-21 14:07:30 +0000635 return 0; // dummy return to suppress warning
John Criswellbd9d3702005-10-27 16:00:10 +0000636}
637
Dan Gohman38415242007-07-16 15:26:22 +0000638static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
639 double V, double W,
640 const Type *Ty) {
641 errno = 0;
642 V = NativeFP(V, W);
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000643 if (errno != 0) {
644 errno = 0;
645 return 0;
Dale Johannesen43421b32007-09-06 18:13:44 +0000646 }
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000647
648 if (Ty == Type::FloatTy)
Chris Lattner02a260a2008-04-20 00:41:09 +0000649 return ConstantFP::get(APFloat((float)V));
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000650 if (Ty == Type::DoubleTy)
Chris Lattner02a260a2008-04-20 00:41:09 +0000651 return ConstantFP::get(APFloat(V));
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000652 assert(0 && "Can only constant fold float/double");
Gabor Greif33e456d2008-05-21 14:07:30 +0000653 return 0; // dummy return to suppress warning
Dan Gohman38415242007-07-16 15:26:22 +0000654}
655
John Criswellbd9d3702005-10-27 16:00:10 +0000656/// ConstantFoldCall - Attempt to constant fold a call to the specified function
657/// with the specified arguments, returning null if unsuccessful.
Dale Johannesen43421b32007-09-06 18:13:44 +0000658
John Criswellbd9d3702005-10-27 16:00:10 +0000659Constant *
Chris Lattnerf286f6f2007-12-10 22:53:04 +0000660llvm::ConstantFoldCall(Function *F,
661 Constant* const* Operands, unsigned NumOperands) {
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000662 const ValueName *NameVal = F->getValueName();
Chris Lattnera099b6c2007-08-08 16:07:23 +0000663 if (NameVal == 0) return 0;
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000664 const char *Str = NameVal->getKeyData();
665 unsigned Len = NameVal->getKeyLength();
666
John Criswellbd9d3702005-10-27 16:00:10 +0000667 const Type *Ty = F->getReturnType();
Chris Lattner72d88ae2007-01-30 23:15:43 +0000668 if (NumOperands == 1) {
John Criswellbd9d3702005-10-27 16:00:10 +0000669 if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
Dale Johannesen43421b32007-09-06 18:13:44 +0000670 if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
671 return 0;
672 /// Currently APFloat versions of these functions do not exist, so we use
673 /// the host native double versions. Float versions are not called
674 /// directly but for all these it is true (float)(f((double)arg)) ==
675 /// f(arg). Long double not supported yet.
676 double V = Ty==Type::FloatTy ? (double)Op->getValueAPF().convertToFloat():
677 Op->getValueAPF().convertToDouble();
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000678 switch (Str[0]) {
679 case 'a':
680 if (Len == 4 && !strcmp(Str, "acos"))
681 return ConstantFoldFP(acos, V, Ty);
682 else if (Len == 4 && !strcmp(Str, "asin"))
683 return ConstantFoldFP(asin, V, Ty);
684 else if (Len == 4 && !strcmp(Str, "atan"))
685 return ConstantFoldFP(atan, V, Ty);
686 break;
687 case 'c':
688 if (Len == 4 && !strcmp(Str, "ceil"))
689 return ConstantFoldFP(ceil, V, Ty);
690 else if (Len == 3 && !strcmp(Str, "cos"))
691 return ConstantFoldFP(cos, V, Ty);
692 else if (Len == 4 && !strcmp(Str, "cosh"))
693 return ConstantFoldFP(cosh, V, Ty);
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000694 else if (Len == 4 && !strcmp(Str, "cosf"))
695 return ConstantFoldFP(cos, V, Ty);
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000696 break;
697 case 'e':
698 if (Len == 3 && !strcmp(Str, "exp"))
699 return ConstantFoldFP(exp, V, Ty);
700 break;
701 case 'f':
702 if (Len == 4 && !strcmp(Str, "fabs"))
Dale Johannesen43421b32007-09-06 18:13:44 +0000703 return ConstantFoldFP(fabs, V, Ty);
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000704 else if (Len == 5 && !strcmp(Str, "floor"))
705 return ConstantFoldFP(floor, V, Ty);
706 break;
707 case 'l':
708 if (Len == 3 && !strcmp(Str, "log") && V > 0)
709 return ConstantFoldFP(log, V, Ty);
710 else if (Len == 5 && !strcmp(Str, "log10") && V > 0)
711 return ConstantFoldFP(log10, V, Ty);
712 else if (!strcmp(Str, "llvm.sqrt.f32") ||
713 !strcmp(Str, "llvm.sqrt.f64")) {
714 if (V >= -0.0)
Dale Johannesen43421b32007-09-06 18:13:44 +0000715 return ConstantFoldFP(sqrt, V, Ty);
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000716 else // Undefined
Chris Lattner02a260a2008-04-20 00:41:09 +0000717 return Constant::getNullValue(Ty);
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000718 }
719 break;
720 case 's':
721 if (Len == 3 && !strcmp(Str, "sin"))
722 return ConstantFoldFP(sin, V, Ty);
723 else if (Len == 4 && !strcmp(Str, "sinh"))
724 return ConstantFoldFP(sinh, V, Ty);
725 else if (Len == 4 && !strcmp(Str, "sqrt") && V >= 0)
726 return ConstantFoldFP(sqrt, V, Ty);
727 else if (Len == 5 && !strcmp(Str, "sqrtf") && V >= 0)
728 return ConstantFoldFP(sqrt, V, Ty);
Chris Lattnerf19f58a2008-03-30 18:02:00 +0000729 else if (Len == 4 && !strcmp(Str, "sinf"))
730 return ConstantFoldFP(sin, V, Ty);
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000731 break;
732 case 't':
733 if (Len == 3 && !strcmp(Str, "tan"))
734 return ConstantFoldFP(tan, V, Ty);
735 else if (Len == 4 && !strcmp(Str, "tanh"))
736 return ConstantFoldFP(tanh, V, Ty);
737 break;
738 default:
739 break;
John Criswellbd9d3702005-10-27 16:00:10 +0000740 }
Reid Spencerb83eb642006-10-20 07:07:24 +0000741 } else if (ConstantInt *Op = dyn_cast<ConstantInt>(Operands[0])) {
Chris Lattnerecc02742007-11-23 22:34:59 +0000742 if (Len > 11 && !memcmp(Str, "llvm.bswap", 10))
Reid Spencere9391fd2007-04-01 07:35:23 +0000743 return ConstantInt::get(Op->getValue().byteSwap());
Chris Lattnerecc02742007-11-23 22:34:59 +0000744 else if (Len > 11 && !memcmp(Str, "llvm.ctpop", 10))
745 return ConstantInt::get(Ty, Op->getValue().countPopulation());
746 else if (Len > 10 && !memcmp(Str, "llvm.cttz", 9))
747 return ConstantInt::get(Ty, Op->getValue().countTrailingZeros());
748 else if (Len > 10 && !memcmp(Str, "llvm.ctlz", 9))
749 return ConstantInt::get(Ty, Op->getValue().countLeadingZeros());
John Criswellbd9d3702005-10-27 16:00:10 +0000750 }
Chris Lattner72d88ae2007-01-30 23:15:43 +0000751 } else if (NumOperands == 2) {
John Criswellbd9d3702005-10-27 16:00:10 +0000752 if (ConstantFP *Op1 = dyn_cast<ConstantFP>(Operands[0])) {
Dale Johannesen9ab7fb32007-10-02 17:43:59 +0000753 if (Ty!=Type::FloatTy && Ty!=Type::DoubleTy)
754 return 0;
Dale Johannesen43421b32007-09-06 18:13:44 +0000755 double Op1V = Ty==Type::FloatTy ?
756 (double)Op1->getValueAPF().convertToFloat():
757 Op1->getValueAPF().convertToDouble();
John Criswellbd9d3702005-10-27 16:00:10 +0000758 if (ConstantFP *Op2 = dyn_cast<ConstantFP>(Operands[1])) {
Dale Johannesen43421b32007-09-06 18:13:44 +0000759 double Op2V = Ty==Type::FloatTy ?
760 (double)Op2->getValueAPF().convertToFloat():
761 Op2->getValueAPF().convertToDouble();
John Criswellbd9d3702005-10-27 16:00:10 +0000762
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000763 if (Len == 3 && !strcmp(Str, "pow")) {
Dan Gohman38415242007-07-16 15:26:22 +0000764 return ConstantFoldBinaryFP(pow, Op1V, Op2V, Ty);
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000765 } else if (Len == 4 && !strcmp(Str, "fmod")) {
Dan Gohman38415242007-07-16 15:26:22 +0000766 return ConstantFoldBinaryFP(fmod, Op1V, Op2V, Ty);
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000767 } else if (Len == 5 && !strcmp(Str, "atan2")) {
Dan Gohman38415242007-07-16 15:26:22 +0000768 return ConstantFoldBinaryFP(atan2, Op1V, Op2V, Ty);
Chris Lattnerb5282dc2007-01-15 06:27:37 +0000769 }
770 } else if (ConstantInt *Op2C = dyn_cast<ConstantInt>(Operands[1])) {
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000771 if (!strcmp(Str, "llvm.powi.f32")) {
Chris Lattner02a260a2008-04-20 00:41:09 +0000772 return ConstantFP::get(APFloat((float)std::pow((float)Op1V,
773 (int)Op2C->getZExtValue())));
Chris Lattnerc5f6a1f2007-08-08 06:55:43 +0000774 } else if (!strcmp(Str, "llvm.powi.f64")) {
Chris Lattner02a260a2008-04-20 00:41:09 +0000775 return ConstantFP::get(APFloat((double)std::pow((double)Op1V,
776 (int)Op2C->getZExtValue())));
Chris Lattnerb5282dc2007-01-15 06:27:37 +0000777 }
John Criswellbd9d3702005-10-27 16:00:10 +0000778 }
779 }
780 }
781 return 0;
782}
783