[NewGVN] Make sure we do not add a user to itself.

If we simplify an instruction to itself, we do not need to add a user to
itself. For congruence classes with a defining expression, we already
use a similar logic.

Fixes PR38259.

Reviewers: davide, efriedma, mcrosier

Reviewed By: davide

Differential Revision: https://reviews.llvm.org/D51168

llvm-svn: 346335

1 files changed, 27 insertions, 0 deletions

diff --git a/llvm/test/Transforms/NewGVN/simp-to-self.ll b/llvm/test/Transforms/NewGVN/simp-to-self.ll
new file mode 100644
index 00000000000..ca46af76849
--- /dev/null
+++ b/llvm/test/Transforms/NewGVN/simp-to-self.ll
@@ -0,0 +1,27 @@
+; RUN: opt -S < %s -newgvn | FileCheck %s
+
+; CHECK-LABEL: for.cond:
+; CHECK-NEXT:    %lv = load i32, i32* bitcast (i64* @a to i32*)
+; CHECK-NEXT:    %bf.clear = and i32 %lv, -131072
+; CHECK-NEXT:    %bf.set = or i32 1, %bf.clear
+; CHECK-NEXT:    br i1 %bc, label %for.cond, label %exit
+@a = external global i64
+
+define void @fn1(i1 %bc) {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.cond1.1, %entry
+  %tmp = phi i1 [ undef, %entry ], [ 1, %for.cond ]
+  %conv = zext i1 %tmp to i32
+  %lv = load i32, i32* bitcast (i64* @a to i32*)
+  %bf.clear = and i32 %lv, -131072
+  %bf.set = or i32 %conv, %bf.clear
+  %bf.clear.1 = and i32 %bf.set, -131072
+  %bf.set.1 = or i32 1, %bf.clear.1
+  br i1 %bc, label %for.cond, label %exit
+
+exit:                              ; preds = %for.cond1
+  store i32 %bf.set.1, i32* bitcast (i64* @a to i32*)
+  ret void
+}