From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Wed, 17 Nov 2010 19:11:46 +0000 (+0000)
Subject: InstCombine: Add a missing irem identity (X % X -> 0).
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=1951a5b721187ab85db0b2db55ae39eec3733c20;p=oota-llvm.git

InstCombine: Add a missing irem identity (X % X -> 0).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119538 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index c2ae4cc6371..1433f7bbc94 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -551,6 +551,10 @@ Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
   if (Instruction *common = commonRemTransforms(I))
     return common;
 
+  // X % X == 0
+  if (Op0 == Op1)
+    return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
+
   // 0 % X == 0 for integer, we don't need to preserve faults!
   if (Constant *LHS = dyn_cast<Constant>(Op0))
     if (LHS->isNullValue())
diff --git a/test/Transforms/InstCombine/rem.ll b/test/Transforms/InstCombine/rem.ll
index bac248e58d7..b421b7c0e8b 100644
--- a/test/Transforms/InstCombine/rem.ll
+++ b/test/Transforms/InstCombine/rem.ll
@@ -81,3 +81,8 @@ define i32 @test12(i32 %i) {
 	%tmp.5 = srem i32 %tmp.1, 2
 	ret i32 %tmp.5
 }
+
+define i32 @test13(i32 %i) {
+	%x = srem i32 %i, %i
+	ret i32 %x
+}