[PATCH] D21318: GlobalsAA: Functions with the argmemonly attribute won't read arbitrary globals

[Tom Stellard via llvm-commits]

tstellarAMD created this revision.
tstellarAMD added reviewers: hfinkel, jmolloy.
tstellarAMD added a subscriber: llvm-commits.

In preparation for changing GlobalsAA to stop assuming that intrinsics
can't read arbitrary globals, we need to make sure GlobalsAA is querying
function attributes rather than relying on this assumption.

This patch was inspired by: http://reviews.llvm.org/D20206

Unfortunately, I was unable to find a test case that this change fixes.  The
tests I added pass even without this change.

http://reviews.llvm.org/D21318

Files:
  lib/Analysis/GlobalsModRef.cpp
  test/Analysis/GlobalsModRef/func-memattributes.ll

Index: test/Analysis/GlobalsModRef/func-memattributes.ll
===================================================================
--- /dev/null
+++ test/Analysis/GlobalsModRef/func-memattributes.ll
@@ -0,0 +1,32 @@
+; RUN: opt < %s -basicaa -globals-aa -dse -S | FileCheck %s
+
+ at X = internal global i32 4
+ at Y = internal global i32 5
+
+define void @test0() {
+; CHECK-LABEL: @test0
+; CHECK: store i32 0, i32* @X
+; CHECK-NEXT: call void @func_readonly(i32* @Y) #0
+; CHECK-NEXT: store i32 1, i32* @X
+  store i32 0, i32* @X
+  call void @func_readonly(i32* @Y) #0
+  store i32 1, i32* @X
+  ret void
+}
+
+define void @test1(i32* %p) {
+; CHECK-LABEL: @test1
+; CHECK-NOT: store
+; CHECK: call void @func_read_argmem_only(i32* @Y) #1
+; CHECK-NEXT: store i32 3, i32* @X
+  store i32 2, i32* @X
+  call void @func_read_argmem_only(i32* @Y) #1
+  store i32 3, i32* @X
+  ret void
+}
+
+declare void @func_readonly(i32*) #0
+declare void @func_read_argmem_only(i32*) #1
+
+attributes #0 = { readonly }
+attributes #1 = { readonly argmemonly }
Index: lib/Analysis/GlobalsModRef.cpp
===================================================================
--- lib/Analysis/GlobalsModRef.cpp
+++ lib/Analysis/GlobalsModRef.cpp
@@ -498,7 +498,7 @@
           // Can't do better than that!
         } else if (F->onlyReadsMemory()) {
           FI.addModRefInfo(MRI_Ref);
-          if (!F->isIntrinsic())
+          if (!F->isIntrinsic() && !F->onlyAccessesArgMemory())
             // This function might call back into the module and read a global -
             // consider every global as possibly being read by this function.
             FI.setMayReadAnyGlobal();


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