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Obey the isVolatile bit on memory intrinsics when analyzing uses of a global
variable. Noticed by inspection. Simulate memset in EvaluateFunction where the target of the memset and the value we're setting are both the null value. Fixes PR10047! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132288 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -241,15 +241,15 @@ static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS,
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GS.HasPHIUser = true;
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} else if (isa<CmpInst>(I)) {
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GS.isCompared = true;
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} else if (isa<MemTransferInst>(I)) {
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const MemTransferInst *MTI = cast<MemTransferInst>(I);
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} else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
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if (MTI->isVolatile()) return true;
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if (MTI->getArgOperand(0) == V)
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GS.StoredType = GlobalStatus::isStored;
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if (MTI->getArgOperand(1) == V)
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GS.isLoaded = true;
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} else if (isa<MemSetInst>(I)) {
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assert(cast<MemSetInst>(I)->getArgOperand(0) == V &&
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"Memset only takes one pointer!");
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} else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
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assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
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if (MSI->isVolatile()) return true;
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GS.StoredType = GlobalStatus::isStored;
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} else {
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return true; // Any other non-load instruction might take address!
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@ -2438,6 +2438,20 @@ static bool EvaluateFunction(Function *F, Constant *&RetVal,
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// Cannot handle inline asm.
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if (isa<InlineAsm>(CI->getCalledValue())) return false;
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if (MemSetInst *MSI = dyn_cast<MemSetInst>(CI)) {
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if (MSI->isVolatile()) return false;
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Constant *Ptr = getVal(Values, MSI->getDest());
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Constant *Val = getVal(Values, MSI->getValue());
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Constant *DestVal = ComputeLoadResult(getVal(Values, Ptr),
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MutatedMemory);
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if (Val->isNullValue() && DestVal->isNullValue()) {
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// This memset is a no-op.
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++CurInst;
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continue;
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}
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return false;
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}
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// Resolve function pointers.
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Function *Callee = dyn_cast<Function>(getVal(Values,
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CI->getCalledValue()));
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19
test/Transforms/GlobalOpt/memset-null.ll
Normal file
19
test/Transforms/GlobalOpt/memset-null.ll
Normal file
@ -0,0 +1,19 @@
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; RUN: opt -globalopt %s -S -o - | FileCheck %s
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; PR10047
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%0 = type { i32, void ()* }
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%struct.A = type { [100 x i32] }
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; CHECK: @a
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@a = global %struct.A zeroinitializer, align 4
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@llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @_GLOBAL__I_a }]
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declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
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; CHECK-NOT: GLOBAL__I_a
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define internal void @_GLOBAL__I_a() nounwind {
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entry:
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tail call void @llvm.memset.p0i8.i64(i8* bitcast (%struct.A* @a to i8*), i8 0, i64 400, i32 4, i1 false) nounwind
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ret void
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}
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