Teach BasicAA about the aliasing properties of memset_pattern16.
Fixes PR10872 and <rdar://problem/10065079>.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139204 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 01257a1..4964c8c 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -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 @@
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<AliasAnalysis>();
+ AU.addRequired<TargetLibraryInfo>();
}
virtual AliasResult alias(const Location &LocA,
@@ -550,9 +552,14 @@
// 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 @@
return NoModRef;
}
+ const TargetLibraryInfo &TLI = getAnalysis<TargetLibraryInfo>();
ModRefResult Min = ModRef;
// Finally, handle specific knowledge of intrinsics.
@@ -819,6 +827,37 @@
}
}
+ // 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);
}