[PATCH] D61517: [InstCombine] Add new combine to add folding.

[Chris Dawson via Phabricator via llvm-commits]

cdawson updated this revision to Diff 198468.
cdawson added a comment.

Updated patch after test pre-commit


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D61517/new/

https://reviews.llvm.org/D61517

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  llvm/test/Transforms/InstCombine/add.ll
  llvm/test/Transforms/InstCombine/sub.ll


Index: llvm/test/Transforms/InstCombine/sub.ll
===================================================================
--- llvm/test/Transforms/InstCombine/sub.ll
+++ llvm/test/Transforms/InstCombine/sub.ll
@@ -1270,9 +1270,8 @@
 ; Check (X | Y) - Y --> X & ~Y when Y is a constant
 define i32 @test70(i32 %A) {
 ; CHECK-LABEL: @test70(
-; CHECK-NEXT:    [[B:%.*]] = or i32 [[A:%.*]], 123
-; CHECK-NEXT:    [[C:%.*]] = add nsw i32 [[B]], -123
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A:%.*]], -124
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %B = or i32 %A, 123
   %C = sub i32 %B, 123
Index: llvm/test/Transforms/InstCombine/add.ll
===================================================================
--- llvm/test/Transforms/InstCombine/add.ll
+++ llvm/test/Transforms/InstCombine/add.ll
@@ -982,9 +982,8 @@
 ; (X | C1) + C2 --> (X | C1) ^ C1 iff (C1 == -C2)
 define i32 @test44(i32 %A) {
 ; CHECK-LABEL: @test44(
-; CHECK-NEXT:    [[B:%.*]] = or i32 [[A:%.*]], 123
-; CHECK-NEXT:    [[C:%.*]] = add nsw i32 [[B]], -123
-; CHECK-NEXT:    ret i32 [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A:%.*]], -124
+; CHECK-NEXT:    ret i32 [[TMP1]]
 ;
   %B = or i32 %A, 123
   %C = add i32 %B, -123
@@ -994,8 +993,8 @@
 define i32 @test44_extra_use(i32 %A) {
 ; CHECK-LABEL: @test44_extra_use(
 ; CHECK-NEXT:    [[B:%.*]] = or i32 [[A:%.*]], 123
-; CHECK-NEXT:    [[C:%.*]] = add nsw i32 [[B]], -123
-; CHECK-NEXT:    [[D:%.*]] = mul i32 [[B]], [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A]], -124
+; CHECK-NEXT:    [[D:%.*]] = mul i32 [[B]], [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[D]]
 ;
   %B = or i32 %A, 123
@@ -1017,9 +1016,8 @@
 
 define <2 x i32> @test44_vec(<2 x i32> %A) {
 ; CHECK-LABEL: @test44_vec(
-; CHECK-NEXT:    [[B:%.*]] = or <2 x i32> [[A:%.*]], <i32 123, i32 123>
-; CHECK-NEXT:    [[C:%.*]] = add nsw <2 x i32> [[B]], <i32 -123, i32 -123>
-; CHECK-NEXT:    ret <2 x i32> [[C]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[A:%.*]], <i32 -124, i32 -124>
+; CHECK-NEXT:    ret <2 x i32> [[TMP1]]
 ;
   %B = or <2 x i32> %A, <i32 123, i32 123>
   %C = add <2 x i32> %B, <i32 -123, i32 -123>
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -892,6 +892,15 @@
   if (!match(Op1, m_APInt(C)))
     return nullptr;
 
+  // (X | C2) + C --> (X | C2) ^ C2
+  // (C2 | X) + C --> (C2 | X) ^ C2
+  // iff (C2 == -C)
+  const APInt *C2;
+  if (match(Op0, m_Or(m_Value(), m_APInt(C2))) &&
+      *C2 == -*C)
+    return BinaryOperator::CreateXor(Op0,
+                                     ConstantInt::get(Add.getType(), *C2));
+
   if (C->isSignMask()) {
     // If wrapping is not allowed, then the addition must set the sign bit:
     // X + (signmask) --> X | signmask
@@ -906,7 +915,6 @@
   // Is this add the last step in a convoluted sext?
   // add(zext(xor i16 X, -32768), -32768) --> sext X
   Type *Ty = Add.getType();
-  const APInt *C2;
   if (match(Op0, m_ZExt(m_Xor(m_Value(X), m_APInt(C2)))) &&
       C2->isMinSignedValue() && C2->sext(Ty->getScalarSizeInBits()) == *C)
     return CastInst::Create(Instruction::SExt, X, Ty);


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