Reapply r52396, it was unrelated to the breakage (that was caused by r52397, my
commit after this).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52453 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/IPConstantPropagation.cpp b/lib/Transforms/IPO/IPConstantPropagation.cpp
index 4ebdaf3..0e654a5 100644
--- a/lib/Transforms/IPO/IPConstantPropagation.cpp
+++ b/lib/Transforms/IPO/IPConstantPropagation.cpp
@@ -21,6 +21,7 @@
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/Statistic.h"
@@ -140,9 +141,10 @@
}
-// Check to see if this function returns a constant. If so, replace all callers
-// that user the return value with the returned valued. If we can replace ALL
-// callers,
+// Check to see if this function returns one or more constants. If so, replace
+// all callers that use those return values with the constant value. This will
+// leave in the actual return values and instructions, but deadargelim will
+// clean that up.
bool IPCP::PropagateConstantReturn(Function &F) {
if (F.getReturnType() == Type::VoidTy)
return false; // No return value.
@@ -156,48 +158,65 @@
SmallVector<Value *,4> RetVals;
const StructType *STy = dyn_cast<StructType>(F.getReturnType());
if (STy)
- RetVals.assign(STy->getNumElements(), 0);
+ for (unsigned i = 0, e = STy->getNumElements(); i < e; ++i)
+ RetVals.push_back(UndefValue::get(STy->getElementType(i)));
else
- RetVals.push_back(0);
+ RetVals.push_back(UndefValue::get(F.getReturnType()));
+ unsigned NumNonConstant = 0;
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- assert(RetVals.size() == RI->getNumOperands() &&
- "Invalid ReturnInst operands!");
+ // Return type does not match operand type, this is an old style multiple
+ // return
+ bool OldReturn = (F.getReturnType() != RI->getOperand(0)->getType());
+
for (unsigned i = 0, e = RetVals.size(); i != e; ++i) {
- if (isa<UndefValue>(RI->getOperand(i)))
- continue; // Ignore
- Constant *C = dyn_cast<Constant>(RI->getOperand(i));
- if (C == 0)
- return false; // Does not return a constant.
-
+ // Already found conflicting return values?
Value *RV = RetVals[i];
- if (RV == 0)
- RetVals[i] = C;
- else if (RV != C)
- return false; // Does not return the same constant.
+ if (!RV)
+ continue;
+
+ // Find the returned value
+ Value *V;
+ if (!STy || OldReturn)
+ V = RI->getOperand(i);
+ else
+ V = FindInsertedValue(RI->getOperand(0), i);
+
+ if (V) {
+ // Ignore undefs, we can change them into anything
+ if (isa<UndefValue>(V))
+ continue;
+
+ // Try to see if all the rets return the same constant.
+ if (isa<Constant>(V)) {
+ if (isa<UndefValue>(RV)) {
+ // No value found yet? Try the current one.
+ RetVals[i] = V;
+ continue;
+ }
+ // Returning the same value? Good.
+ if (RV == V)
+ continue;
+ }
+ }
+ // Different or no known return value? Don't propagate this return
+ // value.
+ RetVals[i] = 0;
+ // All values non constant? Stop looking.
+ if (++NumNonConstant == RetVals.size())
+ return false;
}
}
- if (STy) {
- for (unsigned i = 0, e = RetVals.size(); i < e; ++i)
- if (RetVals[i] == 0)
- RetVals[i] = UndefValue::get(STy->getElementType(i));
- } else {
- assert(RetVals.size() == 1);
- if (RetVals[0] == 0)
- RetVals[0] = UndefValue::get(F.getReturnType());
- }
-
- // If we got here, the function returns a constant value. Loop over all
- // users, replacing any uses of the return value with the returned constant.
- bool ReplacedAllUsers = true;
+ // If we got here, the function returns at least one constant value. Loop
+ // over all users, replacing any uses of the return value with the returned
+ // constant.
bool MadeChange = false;
for (Value::use_iterator UI = F.use_begin(), E = F.use_end(); UI != E; ++UI) {
// Make sure this is an invoke or call and that the use is for the callee.
if (!(isa<InvokeInst>(*UI) || isa<CallInst>(*UI)) ||
UI.getOperandNo() != 0) {
- ReplacedAllUsers = false;
continue;
}
@@ -212,28 +231,32 @@
continue;
}
- while (!Call->use_empty()) {
- GetResultInst *GR = cast<GetResultInst>(Call->use_back());
- GR->replaceAllUsesWith(RetVals[GR->getIndex()]);
- GR->eraseFromParent();
- }
- }
-
- // If we replace all users with the returned constant, and there can be no
- // other callers of the function, replace the constant being returned in the
- // function with an undef value.
- if (ReplacedAllUsers && F.hasInternalLinkage()) {
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
- if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- for (unsigned i = 0, e = RetVals.size(); i < e; ++i) {
- Value *RetVal = RetVals[i];
- if (isa<UndefValue>(RetVal))
- continue;
- Value *RV = UndefValue::get(RetVal->getType());
- if (RI->getOperand(i) != RV) {
- RI->setOperand(i, RV);
- MadeChange = true;
- }
+ for (Value::use_iterator I = Call->use_begin(), E = Call->use_end();
+ I != E;) {
+ Instruction *Ins = dyn_cast<Instruction>(*I);
+
+ // Increment now, so we can remove the use
+ ++I;
+
+ // Not an instruction? Ignore
+ if (!Ins)
+ continue;
+
+ // Find the index of the retval to replace with
+ int index = -1;
+ if (GetResultInst *GR = dyn_cast<GetResultInst>(Ins))
+ index = GR->getIndex();
+ else if (ExtractValueInst *EV = dyn_cast<ExtractValueInst>(Ins))
+ if (EV->hasIndices())
+ index = *EV->idx_begin();
+
+ // If this use uses a specific return value, and we have a replacement,
+ // replace it.
+ if (index != -1) {
+ Value *New = RetVals[index];
+ if (New) {
+ Ins->replaceAllUsesWith(New);
+ Ins->eraseFromParent();
}
}
}