diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 11 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/2008-06-13-ReadOnlyCallStore.ll | 19 |
2 files changed, 25 insertions, 5 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 8dbca0f2e8..8a7128bf65 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -10417,18 +10417,19 @@ bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { return false; break; } - // If we find something that may be using the stored value, or if we run - // out of instructions, we can't do the xform. - if (isa<LoadInst>(BBI) || BBI->mayWriteToMemory() || + // If we find something that may be using or overwriting the stored + // value, or if we run out of instructions, we can't do the xform. + if (BBI->mayReadFromMemory() || BBI->mayWriteToMemory() || BBI == OtherBB->begin()) return false; } // In order to eliminate the store in OtherBr, we have to - // make sure nothing reads the stored value in StoreBB. + // make sure nothing reads or overwrites the stored value in + // StoreBB. for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) { // FIXME: This should really be AA driven. - if (isa<LoadInst>(I) || I->mayWriteToMemory()) + if (I->mayReadFromMemory() || I->mayWriteToMemory()) return false; } } diff --git a/test/Transforms/InstCombine/2008-06-13-ReadOnlyCallStore.ll b/test/Transforms/InstCombine/2008-06-13-ReadOnlyCallStore.ll new file mode 100644 index 0000000000..3f23098225 --- /dev/null +++ b/test/Transforms/InstCombine/2008-06-13-ReadOnlyCallStore.ll @@ -0,0 +1,19 @@ +; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {store i8} | count 2 + +define i32 @a(i8* %s) nounwind { +entry: + store i8 0, i8* %s, align 1 ; This store cannot be eliminated! + %tmp3 = call i32 @strlen( i8* %s ) nounwind readonly + %tmp5 = icmp ne i32 %tmp3, 0 + br i1 %tmp5, label %bb, label %bb8 + +bb: ; preds = %entry + store i8 0, i8* %s, align 1 + br label %bb8 + +bb8: + ret i32 %tmp3 +} + +declare i32 @strlen(i8*) nounwind readonly + |