Add a new pass to simplify specific half_powr function calls. This is
a specialized pass that it not likely to be generally useful.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58732 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/SimplifyHalfPowrLibCalls.cpp b/lib/Transforms/Scalar/SimplifyHalfPowrLibCalls.cpp
new file mode 100644
index 0000000..530ad03
--- /dev/null
+++ b/lib/Transforms/Scalar/SimplifyHalfPowrLibCalls.cpp
@@ -0,0 +1,159 @@
+//===- SimplifyHalfPowrLibCalls.cpp - Optimize specific half_powr calls ---===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a simple pass that applies an experimental
+// transformation on calls to specific functions.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "simplify-libcalls-halfpowr"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Config/config.h"
+using namespace llvm;
+
+namespace {
+ /// This pass optimizes well half_powr function calls.
+ ///
+ class VISIBILITY_HIDDEN SimplifyHalfPowrLibCalls : public FunctionPass {
+ const TargetData *TD;
+ public:
+ static char ID; // Pass identification
+ SimplifyHalfPowrLibCalls() : FunctionPass(&ID) {}
+
+ bool runOnFunction(Function &F);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<TargetData>();
+ }
+
+ Instruction *
+ InlineHalfPowrs(const std::vector<Instruction *> &HalfPowrs,
+ Instruction *InsertPt);
+ };
+ char SimplifyHalfPowrLibCalls::ID = 0;
+} // end anonymous namespace.
+
+static RegisterPass<SimplifyHalfPowrLibCalls>
+X("simplify-libcalls-halfpowr", "Simplify half_powr library calls");
+
+// Public interface to the Simplify HalfPowr LibCalls pass.
+FunctionPass *llvm::createSimplifyHalfPowrLibCallsPass() {
+ return new SimplifyHalfPowrLibCalls();
+}
+
+/// InlineHalfPowrs - Inline a sequence of adjacent half_powr calls, rearranging
+/// their control flow to better facilitate subsequent optimization.
+Instruction *
+SimplifyHalfPowrLibCalls::InlineHalfPowrs(const std::vector<Instruction *> &HalfPowrs,
+ Instruction *InsertPt) {
+ std::vector<BasicBlock *> Bodies;
+ BasicBlock *NewBlock = 0;
+
+ for (unsigned i = 0, e = HalfPowrs.size(); i != e; ++i) {
+ CallInst *Call = cast<CallInst>(HalfPowrs[i]);
+ Function *Callee = Call->getCalledFunction();
+
+ // Minimally sanity-check the CFG of half_powr to ensure that it contains
+ // the the kind of code we expect. If we're running this pass, we have
+ // reason to believe it will be what we expect.
+ Function::iterator I = Callee->begin();
+ BasicBlock *Prologue = I++;
+ if (I == Callee->end()) break;
+ BasicBlock *SubnormalHandling = I++;
+ if (I == Callee->end()) break;
+ BasicBlock *Body = I++;
+ if (I != Callee->end()) break;
+ if (SubnormalHandling->getSinglePredecessor() != Prologue)
+ break;
+ BranchInst *PBI = dyn_cast<BranchInst>(Prologue->getTerminator());
+ if (!PBI || !PBI->isConditional())
+ break;
+ BranchInst *SNBI = dyn_cast<BranchInst>(SubnormalHandling->getTerminator());
+ if (!SNBI || SNBI->isConditional())
+ break;
+ if (!isa<ReturnInst>(Body->getTerminator()))
+ break;
+
+ Instruction *NextInst = next(BasicBlock::iterator(Call));
+
+ // Inline the call, taking care of what code ends up where.
+ NewBlock = SplitBlock(NextInst->getParent(), NextInst, this);
+
+ bool B = InlineFunction(Call, 0, TD);
+ assert(B && "half_powr didn't inline?");
+
+ BasicBlock *NewBody = NewBlock->getSinglePredecessor();
+ assert(NewBody);
+ Bodies.push_back(NewBody);
+ }
+
+ if (!NewBlock)
+ return InsertPt;
+
+ // Put the code for all the bodies into one block, to facilitate
+ // subsequent optimization.
+ (void)SplitEdge(NewBlock->getSinglePredecessor(), NewBlock, this);
+ for (unsigned i = 0, e = Bodies.size(); i != e; ++i) {
+ BasicBlock *Body = Bodies[i];
+ Instruction *FNP = Body->getFirstNonPHI();
+ // Splice the insts from body into NewBlock.
+ NewBlock->getInstList().splice(NewBlock->begin(), Body->getInstList(),
+ FNP, Body->getTerminator());
+ }
+
+ return NewBlock->begin();
+}
+
+/// runOnFunction - Top level algorithm.
+///
+bool SimplifyHalfPowrLibCalls::runOnFunction(Function &F) {
+ TD = &getAnalysis<TargetData>();
+
+ bool Changed = false;
+ std::vector<Instruction *> HalfPowrs;
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ // Look for calls.
+ bool IsHalfPowr = false;
+ if (CallInst *CI = dyn_cast<CallInst>(I)) {
+ // Look for direct calls and calls to non-external functions.
+ Function *Callee = CI->getCalledFunction();
+ if (Callee && Callee->hasExternalLinkage()) {
+ // Look for calls with well-known names.
+ const char *CalleeName = Callee->getNameStart();
+ if (strcmp(CalleeName, "__half_powrf4") == 0)
+ IsHalfPowr = true;
+ }
+ }
+ if (IsHalfPowr)
+ HalfPowrs.push_back(I);
+ // We're looking for sequences of up to three such calls, which we'll
+ // simplify as a group.
+ if ((!IsHalfPowr && !HalfPowrs.empty()) || HalfPowrs.size() == 3) {
+ I = InlineHalfPowrs(HalfPowrs, I);
+ E = I->getParent()->end();
+ HalfPowrs.clear();
+ Changed = true;
+ }
+ }
+ assert(HalfPowrs.empty() && "Block had no terminator!");
+ }
+
+ return Changed;
+}