From 793cd269de49c1d4110940dfb156691be9040bce Mon Sep 17 00:00:00 2001
From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Fri, 11 Feb 2011 21:46:48 +0000
Subject: [PATCH] Also fold (A+B) == A -> B == 0 when the add is commuted.

llvm-svn: 125411
---
 .../InstCombine/InstCombineCompares.cpp       |  6 ++--
 test/Transforms/InstCombine/add.ll            | 30 ++++++++++++-------
 2 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index a24d4ca7eb3..c34e698e3e7 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2351,12 +2351,14 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
                           Constant::getNullValue(B->getType()));
 
     // (A+B) == A  ->  B == 0
-    if (match(Op0, m_Add(m_Specific(Op1), m_Value(B))))
+    if (match(Op0, m_Add(m_Specific(Op1), m_Value(B))) ||
+        match(Op0, m_Add(m_Value(B), m_Specific(Op1))))
       return new ICmpInst(I.getPredicate(), B,
                           Constant::getNullValue(B->getType()));
 
     // A == (A+B)  ->  B == 0
-    if (match(Op1, m_Add(m_Specific(Op0), m_Value(B))))
+    if (match(Op1, m_Add(m_Specific(Op0), m_Value(B))) ||
+        match(Op1, m_Add(m_Value(B), m_Specific(Op0))))
       return new ICmpInst(I.getPredicate(), B,
                           Constant::getNullValue(B->getType()));
 
diff --git a/test/Transforms/InstCombine/add.ll b/test/Transforms/InstCombine/add.ll
index b3a7f526079..a316d06894a 100644
--- a/test/Transforms/InstCombine/add.ll
+++ b/test/Transforms/InstCombine/add.ll
@@ -276,18 +276,26 @@ define i32 @test36(i32 %a) {
 	ret i32 %q
 }
 
-define i32 @test37(i32 %a, i32 %b) nounwind readnone {
-entry:
-  %add = add nsw i32 %a, %b
+define i1 @test37(i32 %a, i32 %b) nounwind readnone {
+  %add = add i32 %a, %b
   %cmp = icmp eq i32 %add, %a
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
+  ret i1 %cmp
 }
 
-define i32 @test38(i32 %a, i32 %b) nounwind readnone {
-entry:
-  %add = add nsw i32 %a, %b
-  %cmp = icmp eq i32 %add, %a
-  %conv = zext i1 %cmp to i32
-  ret i32 %conv
+define i1 @test38(i32 %a, i32 %b) nounwind readnone {
+  %add = add i32 %a, %b
+  %cmp = icmp eq i32 %add, %b
+  ret i1 %cmp
+}
+
+define i1 @test39(i32 %a, i32 %b) nounwind readnone {
+  %add = add i32 %b, %a
+  %cmp = icmp eq i32 %add, %a
+  ret i1 %cmp
+}
+
+define i1 @test40(i32 %a, i32 %b) nounwind readnone {
+  %add = add i32 %b, %a
+  %cmp = icmp eq i32 %add, %b
+  ret i1 %cmp
 }