[PATCH] D60395: [InstCombine] canonicalize sdiv with NEG operand

[ChenZheng via Phabricator via llvm-commits]

shchenz updated this revision to Diff 194094.
shchenz added a comment.

move ***exact* flag fixup code to a seperated patch https://reviews.llvm.org/D60396


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60395/new/

https://reviews.llvm.org/D60395

Files:
  llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll


Index: llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll
===================================================================
--- llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll
+++ llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll
@@ -3,8 +3,8 @@
 
 define i32 @test_sdiv_canonicalize_op0(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test_sdiv_canonicalize_op0(
-; CHECK-NEXT:    [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]]
-; CHECK-NEXT:    [[SDIV:%.*]] = sdiv i32 [[NEG]], [[Y:%.*]]
+; CHECK-NEXT:    [[NEG:%.*]] = sdiv i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sub i32 0, [[NEG]]
 ; CHECK-NEXT:    ret i32 [[SDIV]]
 ;
   %neg = sub nsw i32 0, %x
@@ -15,8 +15,8 @@
 define i32 @test_sdiv_canonicalize_op1(i32 %x, i32 %z) {
 ; CHECK-LABEL: @test_sdiv_canonicalize_op1(
 ; CHECK-NEXT:    [[Y:%.*]] = mul i32 [[Z:%.*]], 3
-; CHECK-NEXT:    [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]]
-; CHECK-NEXT:    [[SDIV:%.*]] = sdiv i32 [[Y]], [[NEG]]
+; CHECK-NEXT:    [[NEG:%.*]] = sdiv i32 [[Y]], [[X:%.*]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sub i32 0, [[NEG]]
 ; CHECK-NEXT:    ret i32 [[SDIV]]
 ;
   %y = mul i32 %z, 3
@@ -38,8 +38,8 @@
 
 define <2 x i32> @test_sdiv_canonicalize_vec(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @test_sdiv_canonicalize_vec(
-; CHECK-NEXT:    [[NEG:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]]
-; CHECK-NEXT:    [[SDIV:%.*]] = sdiv <2 x i32> [[NEG]], [[Y:%.*]]
+; CHECK-NEXT:    [[NEG:%.*]] = sdiv <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sub <2 x i32> zeroinitializer, [[NEG]]
 ; CHECK-NEXT:    ret <2 x i32> [[SDIV]]
 ;
   %neg = sub nsw <2 x i32> <i32 0, i32 0>, %x
Index: llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1021,6 +1021,14 @@
       return new SExtInst(NarrowOp, Op0->getType());
     }
   }
+  
+  // -X / Y --> -(X / Y)
+  // X / -Y --> -(X / Y)
+  Value *Y;
+  if (match(&I, m_SDiv(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y))) ||
+    match(&I, m_SDiv(m_Value(X), m_OneUse(m_NSWSub(m_Zero(), m_Value(Y))))))
+    return BinaryOperator::CreateNeg(
+        Builder.CreateSDiv(X, Y, I.getName(), I.isExact()));
 
   if (Constant *RHS = dyn_cast<Constant>(Op1)) {
     // X/INT_MIN -> X == INT_MIN


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