[llvm] r315718 - [InstCombine] add hasOneUse check to add-zext-add fold to prevent increasing instructions

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Fri Oct 13 10:47:25 2017
New Revision: 315718

URL: http://llvm.org/viewvc/llvm-project?rev=315718&view=rev
Log:
[InstCombine] add hasOneUse check to add-zext-add fold to prevent increasing instructions

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    llvm/trunk/test/Transforms/InstCombine/add.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=315718&r1=315717&r2=315718&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Fri Oct 13 10:47:25 2017
@@ -988,10 +988,8 @@ Instruction *InstCombiner::foldAddWithCo
     return CastInst::Create(Instruction::SExt, X, Ty);
 
   // (add (zext (add nuw X, C2)), C) --> (zext (add nuw X, C2 + C))
-  // FIXME: This should check hasOneUse to not increase the instruction count?
-  if (C->isNegative() &&
-      match(Op0, m_ZExt(m_NUWAdd(m_Value(X), m_APInt(C2)))) &&
-      C->sge(-C2->sext(C->getBitWidth()))) {
+  if (match(Op0, m_OneUse(m_ZExt(m_NUWAdd(m_Value(X), m_APInt(C2))))) &&
+      C->isNegative() && C->sge(-C2->sext(C->getBitWidth()))) {
     Constant *NewC =
         ConstantInt::get(X->getType(), *C2 + C->trunc(C2->getBitWidth()));
     return new ZExtInst(Builder.CreateNUWAdd(X, NewC), Ty);

Modified: llvm/trunk/test/Transforms/InstCombine/add.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/add.ll?rev=315718&r1=315717&r2=315718&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/add.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/add.ll Fri Oct 13 10:47:25 2017
@@ -633,9 +633,8 @@ define <2 x i64> @test41vec_and_multiuse
 ; CHECK-LABEL: @test41vec_and_multiuse(
 ; CHECK-NEXT:    [[ADD:%.*]] = add nuw <2 x i32> %a, <i32 16, i32 16>
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext <2 x i32> [[ADD]] to <2 x i64>
-; CHECK-NEXT:    [[TMP1:%.*]] = add nuw <2 x i32> %a, <i32 15, i32 15>
-; CHECK-NEXT:    [[SUB:%.*]] = zext <2 x i32> [[TMP1]] to <2 x i64>
-; CHECK-NEXT:    [[EXTRAUSE:%.*]] = add nuw nsw <2 x i64> [[ZEXT]], [[SUB]]
+; CHECK-NEXT:    [[SUB:%.*]] = add nsw <2 x i64> [[ZEXT]], <i64 -1, i64 -1>
+; CHECK-NEXT:    [[EXTRAUSE:%.*]] = add nsw <2 x i64> [[SUB]], [[ZEXT]]
 ; CHECK-NEXT:    ret <2 x i64> [[EXTRAUSE]]
 ;
   %add = add nuw <2 x i32> %a, <i32 16, i32 16>