From 60d410d7bb2eb11f36a004237e5948ffc5aff5a6 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 14 Dec 2010 08:01:53 +0000
Subject: fix two significant issues with FoldTwoEntryPHINode:

first, it can kick in on blocks whose conditions have been
folded to a constant, even though one of the edges will be
trivially folded.

second, it doesn't clean up the "if diamond" that it just
eliminated away.  This is a problem because other simplifycfg
xforms kick in depending on the order of block visitation,
causing pointless work.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121762 91177308-0d34-0410-b5e6-96231b3b80d8
---
 test/Transforms/SimplifyCFG/PhiBlockMerge.ll | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

(limited to 'test')

diff --git a/test/Transforms/SimplifyCFG/PhiBlockMerge.ll b/test/Transforms/SimplifyCFG/PhiBlockMerge.ll
index a648efd174..c28d0bac37 100644
--- a/test/Transforms/SimplifyCFG/PhiBlockMerge.ll
+++ b/test/Transforms/SimplifyCFG/PhiBlockMerge.ll
@@ -1,12 +1,14 @@
 ; Test merging of blocks that only have PHI nodes in them
 ;
-; RUN: opt < %s -simplifycfg -S | not grep N:
+; RUN: opt < %s -simplifycfg -S | FileCheck %s
 ;
 
 define i32 @test(i1 %a, i1 %b) {
-; <label>:0
+; CHECK: br i1 %a
         br i1 %a, label %M, label %O
 O:              ; preds = %0
+; CHECK: select i1 %b, i32 0, i32 1
+; CHECK-NOT: phi
         br i1 %b, label %N, label %Q
 Q:              ; preds = %O
         br label %N
@@ -15,6 +17,7 @@ N:              ; preds = %Q, %O
         %Wp = phi i32 [ 0, %O ], [ 1, %Q ]              ; <i32> [#uses=1]
         br label %M
 M:              ; preds = %N, %0
+; CHECK: %W = phi i32
         %W = phi i32 [ %Wp, %N ], [ 2, %0 ]             ; <i32> [#uses=1]
         %R = add i32 %W, 1              ; <i32> [#uses=1]
         ret i32 %R
-- 
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