Move some constant folding logic for loads out of instcombine into
Analysis/ConstantFolding.cpp. This doesn't change the behavior of
instcombine but makes other clients of ConstantFoldInstruction
able to handle loads. This was partially extracted from Eli's patch
in PR3152.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84836 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 60e2d7f..dd313ac 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -11454,6 +11454,7 @@
if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6))
return ReplaceInstUsesWith(LI, AvailableVal);
+ // load(gep null, ...) -> unreachable
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {
const Value *GEPI0 = GEPI->getOperand(0);
// TODO: Consider a target hook for valid address spaces for this xform.
@@ -11468,49 +11469,24 @@
}
}
- if (Constant *C = dyn_cast<Constant>(Op)) {
- // load null/undef -> undef
- // TODO: Consider a target hook for valid address spaces for this xform.
- if (isa<UndefValue>(C) ||
- (C->isNullValue() && LI.getPointerAddressSpace() == 0)) {
- // Insert a new store to null instruction before the load to indicate that
- // this code is not reachable. We do this instead of inserting an
- // unreachable instruction directly because we cannot modify the CFG.
- new StoreInst(UndefValue::get(LI.getType()),
- Constant::getNullValue(Op->getType()), &LI);
- return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
- }
-
- // Instcombine load (constant global) into the value loaded.
- if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
- if (GV->isConstant() && GV->hasDefinitiveInitializer())
- 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->hasDefinitiveInitializer())
- if (Constant *V =
- ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE))
- return ReplaceInstUsesWith(LI, V);
- if (CE->getOperand(0)->isNullValue()) {
- // Insert a new store to null instruction before the load to indicate
- // that this code is not reachable. We do this instead of inserting
- // an unreachable instruction directly because we cannot modify the
- // CFG.
- new StoreInst(UndefValue::get(LI.getType()),
- Constant::getNullValue(Op->getType()), &LI);
- return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
- }
-
- } else if (CE->isCast()) {
- if (Instruction *Res = InstCombineLoadCast(*this, LI, TD))
- return Res;
- }
- }
+ // load null/undef -> unreachable
+ // TODO: Consider a target hook for valid address spaces for this xform.
+ if (isa<UndefValue>(Op) ||
+ (isa<ConstantPointerNull>(Op) && LI.getPointerAddressSpace() == 0)) {
+ // Insert a new store to null instruction before the load to indicate that
+ // this code is not reachable. We do this instead of inserting an
+ // unreachable instruction directly because we cannot modify the CFG.
+ new StoreInst(UndefValue::get(LI.getType()),
+ Constant::getNullValue(Op->getType()), &LI);
+ return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType()));
}
-
+
+ // Instcombine load (constantexpr_cast global) -> cast (load global)
+ if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
+ if (CE->isCast())
+ if (Instruction *Res = InstCombineLoadCast(*this, LI, TD))
+ return Res;
+
// 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())){