From: Chris Lattner <sabre@nondot.org>
Date: Sun, 6 Feb 2011 22:05:31 +0000 (+0000)
Subject: teach instsimplify to transform (X / Y) * Y to X
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c6ee9181a51fdfa3c07e1e53695681c55aa98ce4;p=oota-llvm.git

teach instsimplify to transform (X / Y) * Y to X
when the div is an exact udiv.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124994 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index 220868fe1db..7bb8f699928 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -735,9 +735,11 @@ static Value *SimplifyMulInst(Value *Op0, Value *Op1, const TargetData *TD,
   // (X / Y) * Y -> X if the division is exact.
   Value *X = 0, *Y = 0;
   if ((match(Op0, m_SDiv(m_Value(X), m_Value(Y))) && Y == Op1) || // (X / Y) * Y
-      (match(Op1, m_SDiv(m_Value(X), m_Value(Y))) && Y == Op0)) { // Y * (X / Y)
-    BinaryOperator *SDiv = cast<BinaryOperator>(Y == Op1 ? Op0 : Op1);
-    if (SDiv->isExact())
+      (match(Op0, m_UDiv(m_Value(X), m_Value(Y))) && Y == Op1) ||
+      (match(Op1, m_SDiv(m_Value(X), m_Value(Y))) && Y == Op0) || // Y * (X / Y)
+      (match(Op1, m_UDiv(m_Value(X), m_Value(Y))) && Y == Op0)) {
+    BinaryOperator *Div = cast<BinaryOperator>(Y == Op1 ? Op0 : Op1);
+    if (Div->isExact())
       return X;
   }
 
diff --git a/test/Transforms/InstSimplify/reassociate.ll b/test/Transforms/InstSimplify/reassociate.ll
index 928442ac56c..3c8169e5e28 100644
--- a/test/Transforms/InstSimplify/reassociate.ll
+++ b/test/Transforms/InstSimplify/reassociate.ll
@@ -137,6 +137,7 @@ define i32 @sdiv5(i32 %x, i32 %y) {
 ; CHECK: ret i32 %x
 }
 
+
 define i32 @udiv1(i32 %x, i32 %y) {
 ; CHECK: @udiv1
 ; (no overflow X * Y) / Y -> X
@@ -164,3 +165,22 @@ define i32 @udiv3(i32 %x, i32 %y) {
   ret i32 %div
 ; CHECK: ret i32 0
 }
+
+define i32 @udiv4(i32 %x, i32 %y) {
+; CHECK: @udiv4
+; (X / Y) * Y -> X if the division is exact
+  %div = udiv exact i32 %x, %y
+  %mul = mul i32 %div, %y
+  ret i32 %mul
+; CHECK: ret i32 %x
+}
+
+define i32 @udiv5(i32 %x, i32 %y) {
+; CHECK: @udiv5
+; Y * (X / Y) -> X if the division is exact
+  %div = udiv exact i32 %x, %y
+  %mul = mul i32 %y, %div
+  ret i32 %mul
+; CHECK: ret i32 %x
+}
+