From: Chen Zheng <czhengsz@cn.ibm.com>
Date: Tue, 9 Apr 2019 16:34:31 +0000 (+0000)
Subject: [InstCombine] [InstCombine] Canonicalize (-X s/ Y) to -(X s/ Y).
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c92ab7af6f8abd8f9ed129b454c6d282319f2c48;p=llvm

[InstCombine] [InstCombine] Canonicalize (-X s/ Y) to -(X s/ Y).

Differential Revision: https://reviews.llvm.org/D60395


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358017 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index cb8708446b2..2db6e849b19 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1043,6 +1043,12 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
       Value *NarrowOp = Builder.CreateSDiv(Op0Src, NarrowDivisor);
       return new SExtInst(NarrowOp, Op0->getType());
     }
+  
+  // -X / Y --> -(X / Y)
+  Value *Y;
+  if (match(&I, m_SDiv(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y))))
+    return BinaryOperator::CreateNSWNeg(
+        Builder.CreateSDiv(X, Y, I.getName(), I.isExact()));
 
     // -X / C --> X / -C (if the negation doesn't overflow).
     // TODO: This could be enhanced to handle arbitrary vector constants by
diff --git a/test/Transforms/InstCombine/sdiv-canonicalize.ll b/test/Transforms/InstCombine/sdiv-canonicalize.ll
index 8e1497b900a..39ba5120ed6 100644
--- a/test/Transforms/InstCombine/sdiv-canonicalize.ll
+++ b/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:    [[SDIV1:%.*]] = sdiv i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sub nsw i32 0, [[SDIV1]]
 ; CHECK-NEXT:    ret i32 [[SDIV]]
 ;
   %neg = sub nsw i32 0, %x
@@ -14,8 +14,8 @@ define i32 @test_sdiv_canonicalize_op0(i32 %x, i32 %y) {
 
 define i32 @test_sdiv_canonicalize_op0_exact(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test_sdiv_canonicalize_op0_exact(
-; CHECK-NEXT:    [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]]
-; CHECK-NEXT:    [[SDIV:%.*]] = sdiv exact i32 [[NEG]], [[Y:%.*]]
+; CHECK-NEXT:    [[SDIV1:%.*]] = sdiv exact i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sub nsw i32 0, [[SDIV1]]
 ; CHECK-NEXT:    ret i32 [[SDIV]]
 ;
   %neg = sub nsw i32 0, %x
@@ -23,6 +23,7 @@ define i32 @test_sdiv_canonicalize_op0_exact(i32 %x, i32 %y) {
   ret i32 %sdiv
 }
 
+; (X/-Y) is not equal to -(X/Y), don't canonicalize.
 define i32 @test_sdiv_canonicalize_op1(i32 %x, i32 %z) {
 ; CHECK-LABEL: @test_sdiv_canonicalize_op1(
 ; CHECK-NEXT:    [[Y:%.*]] = mul i32 [[Z:%.*]], 3
@@ -49,8 +50,8 @@ define i32 @test_sdiv_canonicalize_nonsw(i32 %x, i32 %y) {
 
 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:    [[SDIV1:%.*]] = sdiv <2 x i32> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[SDIV:%.*]] = sub nsw <2 x i32> zeroinitializer, [[SDIV1]]
 ; CHECK-NEXT:    ret <2 x i32> [[SDIV]]
 ;
   %neg = sub nsw <2 x i32> <i32 0, i32 0>, %x
@@ -71,9 +72,8 @@ define i32 @test_sdiv_canonicalize_multiple_uses(i32 %x, i32 %y) {
   ret i32 %sdiv2
 }
 
-; There is combination: (X/-CE) -> -(X/CE)
-; There is another combination: -(X/CE) -> (X/-CE)
-; Make sure don't combine them endless.
+; There is combination: -(X/CE) -> (X/-CE).
+; If combines (X/-CE) to -(X/CE), make sure don't combine them endless.
 
 @X = global i32 5