[PATCH] D13962: [OperandBundles] Teach AliasAnalysis about operand bundles

[Sanjoy Das via llvm-commits]

sanjoy created this revision.
sanjoy added reviewers: reames, chandlerc.
sanjoy added a subscriber: llvm-commits.
sanjoy added a dependency: D13961: [OperandBundles] Make function attributes conservatively correct.

If a `CallSite` has operand bundles, then do not peek into the called
function to get a more precise `ModRef` answer.

This is tested using `argmemonly`, `-basicaa` and `-gvn`; but the
functionality is not specific to any of these.

Depends on D13961

http://reviews.llvm.org/D13962

Files:
  include/llvm/Analysis/AliasAnalysis.h
  include/llvm/IR/InstrTypes.h
  test/Feature/OperandBundles/basic-aa-argmemonly.ll

Index: test/Feature/OperandBundles/basic-aa-argmemonly.ll
===================================================================
--- /dev/null
+++ test/Feature/OperandBundles/basic-aa-argmemonly.ll
@@ -0,0 +1,28 @@
+; RUN: opt -S -basicaa -gvn < %s | FileCheck %s
+
+declare void @argmemonly_function(i32 *) argmemonly
+
+define i32 @test0(i32* %P, i32* noalias %P2) {
+; CHECK-LABEL: @test0(
+  %v1 = load i32, i32* %P
+; CHECK: %v1 = load i32, i32* %P
+  call void @argmemonly_function(i32* %P2) [ "tag"() ]
+; CHECK: call void @argmemonly_function(
+  %v2 = load i32, i32* %P
+; CHECK: %v2 = load i32, i32* %P
+  %diff = sub i32 %v1, %v2
+; CHECK: %diff = sub i32 %v1, %v2
+  ret i32 %diff
+; CHECK: ret i32 %diff
+}
+
+define i32 @test1(i32* %P, i32* noalias %P2) {
+; CHECK-LABEL: @test1(
+  %v1 = load i32, i32* %P
+  call void @argmemonly_function(i32* %P2) argmemonly [ "tag"() ]
+; CHECK: call void @argmemonly_function(
+  %v2 = load i32, i32* %P
+  %diff = sub i32 %v1, %v2
+  ret i32 %diff
+; CHECK: ret i32 0
+}
Index: include/llvm/IR/InstrTypes.h
===================================================================
--- include/llvm/IR/InstrTypes.h
+++ include/llvm/IR/InstrTypes.h
@@ -1255,8 +1255,8 @@
   /// \brief Is the function attribute S disallowed by some operand bundle on
   /// this operand bundle user?
   bool isFnAttrDisallowedByOpBundle(StringRef S) const {
-    // Operand bundles only possibly disallow readnone and readonly attributes.
-    // All String attributes are fine.
+    // Operand bundles only possibly disallow readnone, readonly and argmenonly
+    // attributes.  All String attributes are fine.
     return false;
   }
 
@@ -1267,6 +1267,9 @@
     default:
       return false;
 
+    case Attribute::ArgMemOnly:
+      return hasReadingOperandBundles();
+
     case Attribute::ReadNone:
       return hasReadingOperandBundles();
 
Index: include/llvm/Analysis/AliasAnalysis.h
===================================================================
--- include/llvm/Analysis/AliasAnalysis.h
+++ include/llvm/Analysis/AliasAnalysis.h
@@ -759,8 +759,12 @@
   }
 
   FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS) {
-    if (const Function *F = CS.getCalledFunction())
-      return getBestAAResults().getModRefBehavior(F);
+    if (!CS.hasOperandBundles())
+      // If CS has operand bundles then aliasing attributes from the function it
+      // calls do not directly apply to the CallSite.  This can be made more
+      // precise in the future.
+      if (const Function *F = CS.getCalledFunction())
+        return getBestAAResults().getModRefBehavior(F);
 
     return FMRB_UnknownModRefBehavior;
   }


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