Claim NoAlias if two GEPs index different fields of the same struct

Patch by Taewook Oh

Summary: Patch for Bug 27478. Make BasicAliasAnalysis claims NoAlias if two GEPs index different fields of the same structure.

Reviewers: hfinkel, dberlin

Subscribers: dberlin, mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D20665

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@271415 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 36 insertions, 0 deletions

diff --git a/test/Analysis/BasicAA/noalias-structure.ll b/test/Analysis/BasicAA/noalias-structure.ll
new file mode 100644
index 00000000000..201c6f47479
--- /dev/null
+++ b/test/Analysis/BasicAA/noalias-structure.ll
@@ -0,0 +1,36 @@
+; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.Type = type { [10 x i32], i32 }
+@Foo = external global %struct.Type, align 4
+
+; /// Check that BasicAA claims no alias between different fileds of a structure
+; void test() {
+;   for (unsigned i = 0 ; i < 10 ; i++) 
+;     Foo.arr[i] += Foo.i;
+; }
+
+define void @test() {
+; CHECK-LABEL: Function: test:
+entry:
+  %0 = load i32, i32* getelementptr inbounds (%struct.Type, %struct.Type* @Foo, i64 0, i32 1), align 4
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.body
+  ret void
+
+for.body:                                         ; preds = %for.body, %entry
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+
+  %arrayidx = getelementptr inbounds %struct.Type, %struct.Type* @Foo, i64 0, i32 0, i64 %indvars.iv
+  %1 = load i32, i32* %arrayidx, align 4
+  %add = add nsw i32 %1, %0
+  store i32 %add, i32* %arrayidx, align 4
+; CHECK: NoAlias: i32* %arrayidx, i32* getelementptr inbounds (%struct.Type, %struct.Type* @Foo, i64 0, i32 1)
+
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 10
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+}