[PATCH] D61307: [InstCombine] Add new combine to sub folding

[Chris Dawson via Phabricator via llvm-commits]

cdawson updated this revision to Diff 197534.
cdawson added a comment.

Addressed review comments


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D61307/new/

https://reviews.llvm.org/D61307

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
  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
@@ -1267,6 +1267,51 @@
   ret <2 x i32> %res
 }
 
+define i32 @test70(i32 %A) {
+; CHECK-LABEL: @test70(
+; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A:%.*]], -124
+; CHECK-NEXT:    ret i32 [[TMP1]]
+;
+  %B = or i32 %A, 123
+  %C = sub i32 %B, 123
+  ret i32 %C
+}
+
+define i32 @test71(i32 %A, i32 %B) {
+; CHECK-LABEL: @test71(
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B:%.*]], -1
+; CHECK-NEXT:    [[D:%.*]] = and i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    ret i32 [[D]]
+;
+  %C = or i32 %A, %B
+  %D = sub i32 %C, %B
+  ret i32 %D
+}
+
+define i32 @test72(i32 %A, i32 %B) {
+; CHECK-LABEL: @test72(
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B:%.*]], -1
+; CHECK-NEXT:    [[D:%.*]] = and i32 [[TMP1]], [[A:%.*]]
+; CHECK-NEXT:    ret i32 [[D]]
+;
+  %C = or i32 %B, %A
+  %D = sub i32 %C, %B
+  ret i32 %D
+}
+
+define i32 @test73(i32 %A, i32 %B) {
+; CHECK-LABEL: @test73(
+; CHECK-NEXT:    [[C:%.*]] = or i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[D:%.*]] = xor i32 [[C]], [[B]]
+; CHECK-NEXT:    [[E:%.*]] = mul i32 [[C]], [[D]]
+; CHECK-NEXT:    ret i32 [[E]]
+;
+  %C = or i32 %A, %B
+  %D = sub i32 %C, %B
+  %E = mul i32 %C, %D
+  ret i32 %E
+}
+
 define i32 @nsw_inference1(i32 %x, i32 %y) {
 ; CHECK-LABEL: @nsw_inference1(
 ; CHECK-NEXT:    [[X2:%.*]] = or i32 [[X:%.*]], 1024
Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1528,8 +1528,13 @@
   if (Value *V = SimplifyUsingDistributiveLaws(I))
     return replaceInstUsesWith(I, V);
 
-  // If this is a 'B = x-(-A)', change to B = x+A.
   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+  // (X | Y) - Y --> (X | Y) ^ Y
+  // (Y | X) - Y --> (Y | X) ^ Y
+  if (match(Op0, m_c_Or(m_Specific(Op1), m_Value())))
+    return BinaryOperator::CreateXor(Op0, Op1);
+
+  // If this is a 'B = x-(-A)', change to B = x+A.
   if (Value *V = dyn_castNegVal(Op1)) {
     BinaryOperator *Res = BinaryOperator::CreateAdd(Op0, V);
 


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