Make ModRefBehavior a lattice. Use this to clean up AliasAnalysis
chaining and simplify FunctionAttrs' GetModRefBehavior logic.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118660 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp
index 8bdf5d7..3b1b13d 100644
--- a/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -128,54 +128,41 @@
// Ignore calls to functions in the same SCC.
if (CS.getCalledFunction() && SCCNodes.count(CS.getCalledFunction()))
continue;
- switch (AA->getModRefBehavior(CS)) {
- case AliasAnalysis::DoesNotAccessMemory:
- // Ignore calls that don't access memory.
- continue;
- case AliasAnalysis::OnlyReadsMemory:
- // Handle calls that only read from memory.
- ReadsMemory = true;
- continue;
- case AliasAnalysis::AccessesArguments:
- // Check whether all pointer arguments point to local memory, and
- // ignore calls that only access local memory.
- for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
- CI != CE; ++CI) {
- Value *Arg = *CI;
- if (Arg->getType()->isPointerTy()) {
- AliasAnalysis::Location Loc(Arg,
- AliasAnalysis::UnknownSize,
- I->getMetadata(LLVMContext::MD_tbaa));
- if (!AA->pointsToConstantMemory(Loc, /*OrLocal=*/true))
- // Writes memory. Just give up.
- return false;
- }
- }
- // Only reads and writes local memory.
- continue;
- case AliasAnalysis::AccessesArgumentsReadonly:
- // Check whether all pointer arguments point to local memory, and
- // ignore calls that only access local memory.
- for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
- CI != CE; ++CI) {
- Value *Arg = *CI;
- if (Arg->getType()->isPointerTy()) {
- AliasAnalysis::Location Loc(Arg,
- AliasAnalysis::UnknownSize,
- I->getMetadata(LLVMContext::MD_tbaa));
- if (!AA->pointsToConstantMemory(Loc, /*OrLocal=*/true)) {
- // Reads non-local memory.
- ReadsMemory = true;
- break;
+ AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(CS);
+ // If the call doesn't access arbitrary memory, we may be able to
+ // figure out something.
+ if (!(MRB & AliasAnalysis::Anywhere &
+ ~AliasAnalysis::ArgumentPointees)) {
+ // If the call accesses argument pointees, check each argument.
+ if (MRB & AliasAnalysis::AccessesArguments)
+ // Check whether all pointer arguments point to local memory, and
+ // ignore calls that only access local memory.
+ for (CallSite::arg_iterator CI = CS.arg_begin(), CE = CS.arg_end();
+ CI != CE; ++CI) {
+ Value *Arg = *CI;
+ if (Arg->getType()->isPointerTy()) {
+ AliasAnalysis::Location Loc(Arg,
+ AliasAnalysis::UnknownSize,
+ I->getMetadata(LLVMContext::MD_tbaa));
+ if (!AA->pointsToConstantMemory(Loc, /*OrLocal=*/true)) {
+ if (MRB & AliasAnalysis::Mod)
+ // Writes non-local memory. Give up.
+ return false;
+ if (MRB & AliasAnalysis::Ref)
+ // Ok, it reads non-local memory.
+ ReadsMemory = true;
+ }
}
}
- }
- // Only reads memory.
continue;
- default:
- // Otherwise, be conservative.
- break;
}
+ // The call could access any memory. If that includes writes, give up.
+ if (MRB & AliasAnalysis::Mod)
+ return false;
+ // If it reads, note it.
+ if (MRB & AliasAnalysis::Ref)
+ ReadsMemory = true;
+ continue;
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
// Ignore non-volatile loads from local memory.
if (!LI->isVolatile()) {