[Sink] Don't move calls to readonly functions across stores

Summary:

Reviewers: hfinkel, majnemer, tstellarAMD, sunfish

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D17279

llvm-svn: 275066

2 files changed, 118 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/Sink.cpp b/llvm/lib/Transforms/Scalar/Sink.cpp
index 5fa43bda9d0..d9a296c6312 100644
--- a/llvm/lib/Transforms/Scalar/Sink.cpp
+++ b/llvm/lib/Transforms/Scalar/Sink.cpp
@@ -76,11 +76,15 @@ static bool isSafeToMove(Instruction *Inst, AliasAnalysis &AA,
       Inst->mayThrow())
     return false;
 
-  // Convergent operations cannot be made control-dependent on additional
-  // values.
   if (auto CS = CallSite(Inst)) {
+    // Convergent operations cannot be made control-dependent on additional
+    // values.
     if (CS.hasFnAttr(Attribute::Convergent))
       return false;
+
+    for (Instruction *S : Stores)
+      if (AA.getModRefInfo(S, CS) & MRI_Mod)
+        return false;
   }
 
   return true;
diff --git a/llvm/test/Transforms/Sink/call.ll b/llvm/test/Transforms/Sink/call.ll
new file mode 100644
index 00000000000..5aaad4499f5
--- /dev/null
+++ b/llvm/test/Transforms/Sink/call.ll
@@ -0,0 +1,112 @@
+; RUN: opt < %s -basicaa -sink -S | FileCheck %s
+
+declare i32 @f_load_global() nounwind readonly
+declare i32 @f_load_arg(i32*) nounwind readonly argmemonly
+declare void @f_store_global(i32) nounwind
+declare void @f_store_arg(i32*) nounwind argmemonly
+declare void @f_readonly_arg(i32* readonly, i32*) nounwind argmemonly
+declare i32 @f_readnone(i32) nounwind readnone
+
+@A = external global i32
+@B = external global i32
+
+; Sink readonly call if no stores are in the way.
+;
+; CHECK-LABEL: @test_sink_no_stores(
+; CHECK: true:
+; CHECK-NEXT: %l = call i32 @f_load_global
+; CHECK-NEXT: ret i32 %l
+define i32 @test_sink_no_stores(i1 %z) {
+  %l = call i32 @f_load_global()
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}
+
+; CHECK-LABEL: @test_sink_argmem_store(
+; CHECK: true:
+; CHECK-NEXT: %l = call i32 @f_load_arg
+; CHECK-NEXT: ret i32 %l
+define i32 @test_sink_argmem_store(i1 %z) {
+  %l = call i32 @f_load_arg(i32* @A)
+  store i32 0, i32* @B
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}
+
+; CHECK-LABEL: @test_sink_argmem_call(
+; CHECK: true:
+; CHECK-NEXT: %l = call i32 @f_load_arg
+; CHECK-NEXT: ret i32 %l
+define i32 @test_sink_argmem_call(i1 %z) {
+  %l = call i32 @f_load_arg(i32* @A)
+  call void @f_store_arg(i32* @B)
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}
+
+; CHECK-LABEL: @test_sink_argmem_multiple(
+; CHECK: true:
+; CHECK-NEXT: %l = call i32 @f_load_arg
+; CHECK-NEXT: ret i32 %l
+define i32 @test_sink_argmem_multiple(i1 %z) {
+  %l = call i32 @f_load_arg(i32* @A)
+  call void @f_readonly_arg(i32* @A, i32* @B)
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}
+
+; But don't sink if there is a store.
+;
+; CHECK-LABEL: @test_nosink_store(
+; CHECK: call i32 @f_load_global
+; CHECK-NEXT: store i32
+define i32 @test_nosink_store(i1 %z) {
+  %l = call i32 @f_load_global()
+  store i32 0, i32* @A
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}
+
+; CHECK-LABEL: @test_nosink_call(
+; CHECK: call i32 @f_load_global
+; CHECK-NEXT: call void @f_store_global
+define i32 @test_nosink_call(i1 %z) {
+  %l = call i32 @f_load_global()
+  call void @f_store_global(i32 0)
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}
+
+; readnone calls are sunk across stores.
+;
+; CHECK-LABEL: @test_sink_readnone(
+; CHECK: true:
+; CHECK-NEXT: %l = call i32 @f_readnone(
+; CHECK-NEXT: ret i32 %l
+define i32 @test_sink_readnone(i1 %z) {
+  %l = call i32 @f_readnone(i32 0)
+  store i32 0, i32* @A
+  br i1 %z, label %true, label %false
+true:
+  ret i32 %l
+false:
+  ret i32 0
+}