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Don't load values out of global constants with weak

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linkage: the value may be replaced with something
different at link time.  (Frontends that want to
allow values to be loaded out of weak constants can
give their constants weak_odr linkage).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67407 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands
2009-03-20 21:53:29 +00:00
parent db95fa131a
commit ab6b226978
5 changed files with 58 additions and 6 deletions
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7
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -11215,14 +11215,15 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
// Instcombine load (constant global) into the value loaded.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
if (GV->isConstant() && !GV->isDeclaration())
if (GV->isConstant() && !GV->isDeclaration() && !GV->mayBeOverridden())
return ReplaceInstUsesWith(LI, GV->getInitializer());
// Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
if (GV->isConstant() && !GV->isDeclaration())
if (GV->isConstant() && !GV->isDeclaration() &&
!GV->mayBeOverridden())
if (Constant *V =
ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
return ReplaceInstUsesWith(LI, V);
@ -11246,7 +11247,7 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
// If this load comes from anywhere in a constant global, and if the global
// is all undef or zero, we know what it loads.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op->getUnderlyingObject())){
if (GV->isConstant() && GV->hasInitializer()) {
if (GV->isConstant() && GV->hasInitializer() && !GV->mayBeOverridden()) {
if (GV->getInitializer()->isNullValue())
return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));
else if (isa<UndefValue>(GV->getInitializer()))