Be more careful about invariance reasoning on "store" queries. Stores still need
to depend on Ref and ModRef calls within the invariant region.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85380 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index edead09..be5f9c1 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -230,12 +230,11 @@
return MemDepResult::getDef(Inst);
}
- // If we're querying on a store and we're in an invariant region, we're done
- // at this point. The only things that stores depend on that could exist in
- // an invariant region are loads, which we've already checked.
- if (invariantTag) continue;
-
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ // There can't be stores to the value we care about inside an
+ // invariant region.
+ if (invariantTag) continue;
+
// If alias analysis can tell that this store is guaranteed to not modify
// the query pointer, ignore it. Use getModRefInfo to handle cases where
// the query pointer points to constant memory etc.
@@ -280,12 +279,16 @@
case AliasAnalysis::NoModRef:
// If the call has no effect on the queried pointer, just ignore it.
continue;
+ case AliasAnalysis::Mod:
+ // If we're in an invariant region, we can ignore calls that ONLY
+ // modify the pointer.
+ if (invariantTag) continue;
+ return MemDepResult::getClobber(Inst);
case AliasAnalysis::Ref:
// If the call is known to never store to the pointer, and if this is a
// load query, we can safely ignore it (scan past it).
if (isLoad)
continue;
- // FALL THROUGH.
default:
// Otherwise, there is a potential dependence. Return a clobber.
return MemDepResult::getClobber(Inst);
diff --git a/test/Transforms/GVN/invariant-simple.ll b/test/Transforms/GVN/invariant-simple.ll
index c3ff353..6de75f1 100644
--- a/test/Transforms/GVN/invariant-simple.ll
+++ b/test/Transforms/GVN/invariant-simple.ll
@@ -16,6 +16,21 @@
ret i8 %2
}
+define i8 @test2(i8* %P) nounwind {
+; CHECK: @test2
+; CHECK: store i8 1
+; CHECK: store i8 2
+; CHECK: ret i8 0
+entry:
+ store i8 1, i8* %P
+ %0 = call {}* @llvm.invariant.start(i64 32, i8* %P)
+ %1 = tail call i32 @bar(i8* %P)
+ call void @llvm.invariant.end({}* %0, i64 32, i8* %P)
+ store i8 2, i8* %P
+ ret i8 0
+}
+
declare i32 @foo(i8*) nounwind
+declare i32 @bar(i8*) nounwind readonly
declare {}* @llvm.invariant.start(i64 %S, i8* nocapture %P) readonly
declare void @llvm.invariant.end({}* %S, i64 %SS, i8* nocapture %P)
\ No newline at end of file