[llvm] r335527 - [InstCombine] fold sdiv with sext bool divisor

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Mon Jun 25 14:39:41 2018
New Revision: 335527

URL: http://llvm.org/viewvc/llvm-project?rev=335527&view=rev
Log:
[InstCombine] fold sdiv with sext bool divisor

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
    llvm/trunk/test/Transforms/InstCombine/div.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=335527&r1=335526&r2=335527&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp Mon Jun 25 14:39:41 2018
@@ -1019,12 +1019,15 @@ Instruction *InstCombiner::visitSDiv(Bin
     return Common;
 
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+  Value *X;
+  // sdiv Op0, -1 --> -Op0
+  // sdiv Op0, (sext i1 X) --> -Op0 (because if X is 0, the op is undefined)
+  if (match(Op1, m_AllOnes()) ||
+      (match(Op1, m_SExt(m_Value(X))) && X->getType()->isIntOrIntVectorTy(1)))
+    return BinaryOperator::CreateNeg(Op0);
+
   const APInt *Op1C;
   if (match(Op1, m_APInt(Op1C))) {
-    // sdiv X, -1 == -X
-    if (Op1C->isAllOnesValue())
-      return BinaryOperator::CreateNeg(Op0);
-
     // sdiv exact X, C  -->  ashr exact X, log2(C)
     if (I.isExact() && Op1C->isNonNegative() && Op1C->isPowerOf2()) {
       Value *ShAmt = ConstantInt::get(Op1->getType(), Op1C->exactLogBase2());

Modified: llvm/trunk/test/Transforms/InstCombine/div.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/div.ll?rev=335527&r1=335526&r2=335527&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/div.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/div.ll Mon Jun 25 14:39:41 2018
@@ -48,8 +48,7 @@ define <2 x i64> @sdiv_by_minus1_vec_und
 
 define i32 @sdiv_by_sext_minus1(i1 %x, i32 %y) {
 ; CHECK-LABEL: @sdiv_by_sext_minus1(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext i1 [[X:%.*]] to i32
-; CHECK-NEXT:    [[DIV:%.*]] = sdiv i32 [[Y:%.*]], [[SEXT]]
+; CHECK-NEXT:    [[DIV:%.*]] = sub i32 0, [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[DIV]]
 ;
   %sext = sext i1 %x to i32
@@ -59,8 +58,7 @@ define i32 @sdiv_by_sext_minus1(i1 %x, i
 
 define <2 x i32> @sdiv_by_sext_minus1_vec(<2 x i1> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @sdiv_by_sext_minus1_vec(
-; CHECK-NEXT:    [[SEXT:%.*]] = sext <2 x i1> [[X:%.*]] to <2 x i32>
-; CHECK-NEXT:    [[DIV:%.*]] = sdiv <2 x i32> [[Y:%.*]], [[SEXT]]
+; CHECK-NEXT:    [[DIV:%.*]] = sub <2 x i32> zeroinitializer, [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[DIV]]
 ;
   %sext = sext <2 x i1> %x to <2 x i32>