[llvm] r358328 - [InstCombine] Canonicalize (-X srem Y) to -(X srem Y).

[Chen Zheng via llvm-commits]

Author: shchenz
Date: Sat Apr 13 02:21:22 2019
New Revision: 358328

URL: http://llvm.org/viewvc/llvm-project?rev=358328&view=rev
Log:
[InstCombine] Canonicalize (-X srem Y) to -(X srem Y).

Differential Revision: https://reviews.llvm.org/D60647

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
    llvm/trunk/test/Transforms/InstCombine/srem-canonicalize.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=358328&r1=358327&r2=358328&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp Sat Apr 13 02:21:22 2019
@@ -1351,6 +1351,11 @@ Instruction *InstCombiner::visitSRem(Bin
     }
   }
 
+  // -X srem Y --> -(X srem Y)
+  Value *X, *Y;
+  if (match(&I, m_SRem(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y))))
+    return BinaryOperator::CreateNSWNeg(Builder.CreateSRem(X, Y)); 
+
   // If the sign bits of both operands are zero (i.e. we can prove they are
   // unsigned inputs), turn this into a urem.
   APInt Mask(APInt::getSignMask(I.getType()->getScalarSizeInBits()));

Modified: llvm/trunk/test/Transforms/InstCombine/srem-canonicalize.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/srem-canonicalize.ll?rev=358328&r1=358327&r2=358328&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/srem-canonicalize.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/srem-canonicalize.ll Sat Apr 13 02:21:22 2019
@@ -3,8 +3,8 @@
 
 define i32 @test_srem_canonicalize_op0(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test_srem_canonicalize_op0(
-; CHECK-NEXT:    [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]]
-; CHECK-NEXT:    [[SREM:%.*]] = srem i32 [[NEG]], [[Y:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = srem i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SREM:%.*]] = sub nsw i32 0, [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[SREM]]
 ;
   %neg = sub nsw i32 0, %x
@@ -39,8 +39,8 @@ define i32 @test_srem_canonicalize_nonsw
 
 define <2 x i32> @test_srem_canonicalize_vec(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @test_srem_canonicalize_vec(
-; CHECK-NEXT:    [[NEG:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
-; CHECK-NEXT:    [[SREM:%.*]] = srem <2 x i32> [[NEG]], [[Y:%.*]]
+; CHECK-NEXT:    [[TMP1:%.*]] = srem <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SREM:%.*]] = sub nsw <2 x i32> zeroinitializer, [[TMP1]]
 ; CHECK-NEXT:    ret <2 x i32> [[SREM]]
 ;
   %neg = sub nsw <2 x i32> <i32 0, i32 0>, %x