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Teach BasicAA about the aliasing properties of memset_pattern16.

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Fixes PR10872 and <rdar://problem/10065079>.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139204 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2011-09-06 23:33:25 +00:00
parent 218affc710
commit 69acc93b3d
2 changed files with 61 additions and 1 deletions
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41
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -30,6 +30,7 @@
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/ErrorHandling.h"
@ -468,6 +469,7 @@ namespace {
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<AliasAnalysis>();
AU.addRequired<TargetLibraryInfo>();
}
virtual AliasResult alias(const Location &LocA,
@ -550,9 +552,14 @@ namespace {
// Register this pass...
char BasicAliasAnalysis::ID = 0;
INITIALIZE_AG_PASS(BasicAliasAnalysis, AliasAnalysis, "basicaa",
INITIALIZE_AG_PASS_BEGIN(BasicAliasAnalysis, AliasAnalysis, "basicaa",
"Basic Alias Analysis (stateless AA impl)",
false, true, false)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_AG_PASS_END(BasicAliasAnalysis, AliasAnalysis, "basicaa",
"Basic Alias Analysis (stateless AA impl)",
false, true, false)
ImmutablePass *llvm::createBasicAliasAnalysisPass() {
return new BasicAliasAnalysis();
@ -717,6 +724,7 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
return NoModRef;
}
const TargetLibraryInfo &TLI = getAnalysis<TargetLibraryInfo>();
ModRefResult Min = ModRef;
// Finally, handle specific knowledge of intrinsics.
@ -819,6 +827,37 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
}
}
// We can bound the aliasing properties of memset_pattern16 just as we can
// for memcpy/memset. This is particularly important because the
// LoopIdiomRecognizer likes to turn loops into calls to memset_pattern16
// whenever possible.
else if (TLI.has(LibFunc::memset_pattern16) &&
CS.getCalledFunction() &&
CS.getCalledFunction()->getName() == "memset_pattern16") {
const Function *MS = CS.getCalledFunction();
FunctionType *MemsetType = MS->getFunctionType();
if (!MemsetType->isVarArg() && MemsetType->getNumParams() == 3 &&
isa<PointerType>(MemsetType->getParamType(0)) &&
isa<PointerType>(MemsetType->getParamType(1)) &&
isa<IntegerType>(MemsetType->getParamType(2))) {
uint64_t Len = UnknownSize;
if (const ConstantInt *LenCI = dyn_cast<ConstantInt>(CS.getArgument(2)))
Len = LenCI->getZExtValue();
const Value *Dest = CS.getArgument(0);
const Value *Src = CS.getArgument(1);
// If it can't overlap the source dest, then it doesn't modref the loc.
if (isNoAlias(Location(Dest, Len), Loc)) {
if (isNoAlias(Location(Src, 2), Loc))
return NoModRef;
// If it can't overlap the dest, then worst case it reads the loc.
Min = Ref;
} else if (isNoAlias(Location(Src, 2), Loc)) {
// If it can't overlap the source, then worst case it mutates the loc.
Min = Mod;
}
}
}
// The AliasAnalysis base class has some smarts, lets use them.
return ModRefResult(AliasAnalysis::getModRefInfo(CS, Loc) & Min);
}

21
test/Analysis/BasicAA/memset_pattern.ll Normal file
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@ -0,0 +1,21 @@
; RUN: opt -S -basicaa -gvn < %s | FileCheck %s
; PR10872
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-macosx10.7"
@z = internal global i32 0, align 4
@y = internal global i32 0, align 4
@x = internal constant i32 0, align 4
; CHECK: @test
define i32 @test() nounwind uwtable ssp {
entry:
store i32 1, i32* @z
tail call void @memset_pattern16(i8* bitcast (i32* @y to i8*), i8* bitcast (i32* @x to i8*), i64 4) nounwind
; CHECK-NOT: load
%l = load i32* @z
; CHECK: ret i32 1
ret i32 %l
}
declare void @memset_pattern16(i8*, i8*, i64)