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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!

llvm-svn: 132288
This commit is contained in:
Nick Lewycky 2011-05-29 18:41:56 +00:00
parent 28d55e0745
commit a3bb03e400
2 changed files with 38 additions and 5 deletions
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24
llvm/lib/Transforms/IPO/GlobalOpt.cpp
View File

@ -241,15 +241,15 @@ static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS,
GS.HasPHIUser = true; GS.HasPHIUser = true;
} else if (isa<CmpInst>(I)) { } else if (isa<CmpInst>(I)) {
GS.isCompared = true; GS.isCompared = true;
} else if (isa<MemTransferInst>(I)) { } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
const MemTransferInst *MTI = cast<MemTransferInst>(I); if (MTI->isVolatile()) return true;
if (MTI->getArgOperand(0) == V) if (MTI->getArgOperand(0) == V)
GS.StoredType = GlobalStatus::isStored; GS.StoredType = GlobalStatus::isStored;
if (MTI->getArgOperand(1) == V) if (MTI->getArgOperand(1) == V)
GS.isLoaded = true; GS.isLoaded = true;
} else if (isa<MemSetInst>(I)) { } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
assert(cast<MemSetInst>(I)->getArgOperand(0) == V && assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
"Memset only takes one pointer!"); if (MSI->isVolatile()) return true;
GS.StoredType = GlobalStatus::isStored; GS.StoredType = GlobalStatus::isStored;
} else { } else {
return true; // Any other non-load instruction might take address! return true; // Any other non-load instruction might take address!
@ -2438,6 +2438,20 @@ static bool EvaluateFunction(Function *F, Constant *&RetVal,
// Cannot handle inline asm. // Cannot handle inline asm.
if (isa<InlineAsm>(CI->getCalledValue())) return false; if (isa<InlineAsm>(CI->getCalledValue())) return false;
if (MemSetInst *MSI = dyn_cast<MemSetInst>(CI)) {
if (MSI->isVolatile()) return false;
Constant *Ptr = getVal(Values, MSI->getDest());
Constant *Val = getVal(Values, MSI->getValue());
Constant *DestVal = ComputeLoadResult(getVal(Values, Ptr),
MutatedMemory);
if (Val->isNullValue() && DestVal->isNullValue()) {
// This memset is a no-op.
++CurInst;
continue;
}
return false;
}
// Resolve function pointers. // Resolve function pointers.
Function *Callee = dyn_cast<Function>(getVal(Values, Function *Callee = dyn_cast<Function>(getVal(Values,
CI->getCalledValue())); CI->getCalledValue()));

19
llvm/test/Transforms/GlobalOpt/memset-null.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: opt -globalopt %s -S -o - | FileCheck %s
; PR10047
%0 = type { i32, void ()* }
%struct.A = type { [100 x i32] }
; CHECK: @a
@a = global %struct.A zeroinitializer, align 4
@llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @_GLOBAL__I_a }]
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
; CHECK-NOT: GLOBAL__I_a
define internal void @_GLOBAL__I_a() nounwind {
entry:
tail call void @llvm.memset.p0i8.i64(i8* bitcast (%struct.A* @a to i8*), i8 0, i64 400, i32 4, i1 false) nounwind
ret void
}