[PATCH] D113945: [InstSimplify] Fold A|B | (A^B) --> A|B

[Mehrnoosh Heidarpour via Phabricator via llvm-commits]

MehrHeidar created this revision.
MehrHeidar added reviewers: foad, spatel.
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This patch adds the following fold opportunity:
A|B | (A^B) --> A|B

that is reported here : https://bugs.llvm.org/show_bug.cgi?id=52479

https://alive2.llvm.org/ce/z/33-My-

Test cases with base results are added in D113860 <https://reviews.llvm.org/D113860>

Previously authored in D113861 <https://reviews.llvm.org/D113861>, but due to  committing with not giving the credits has been reverted.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113945

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/or.ll


Index: llvm/test/Transforms/InstSimplify/or.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/or.ll
+++ llvm/test/Transforms/InstSimplify/or.ll
@@ -451,9 +451,7 @@
 define i69 @or_or_xor(i69 %A, i69 %B) {
 ; CHECK-LABEL: @or_or_xor(
 ; CHECK-NEXT:    [[I1:%.*]] = or i69 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[I2:%.*]] = xor i69 [[A]], [[B]]
-; CHECK-NEXT:    [[I3:%.*]] = or i69 [[I1]], [[I2]]
-; CHECK-NEXT:    ret i69 [[I3]]
+; CHECK-NEXT:    ret i69 [[I1]]
 ;
   %i1 = or i69 %A, %B
   %i2 = xor i69 %A, %B
@@ -461,12 +459,25 @@
   ret i69 %i3
 }
 
+; (B | A) | (A ^ B) --> B | A
+
+define i8 @or_or_xor_inner_or_commuted(i8 %A, i8 %B) {
+; CHECK-LABEL: @or_or_xor_inner_or_commuted(
+; CHECK-NEXT:    [[I1:%.*]] = or i8 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT:    ret i8 [[I1]]
+;
+  %i1 = or i8 %B, %A
+  %i2 = xor i8 %A, %B
+  %i3 = or i8 %i1, %i2
+  ret i8 %i3
+}
+
+; (A ^ B) | (A | B) --> A | B
+
 define <4 x i4> @or_or_xor_commuted(<4 x i4> %A, <4 x i4> %B) {
 ; CHECK-LABEL: @or_or_xor_commuted(
 ; CHECK-NEXT:    [[I1:%.*]] = or <4 x i4> [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[I2:%.*]] = xor <4 x i4> [[A]], [[B]]
-; CHECK-NEXT:    [[I3:%.*]] = or <4 x i4> [[I2]], [[I1]]
-; CHECK-NEXT:    ret <4 x i4> [[I3]]
+; CHECK-NEXT:    ret <4 x i4> [[I1]]
 ;
   %i1 = or <4 x i4> %A, %B
   %i2 = xor <4 x i4> %A, %B
@@ -474,6 +485,19 @@
   ret <4 x i4> %i3
 }
 
+; (A ^ B) | (B | A) --> B | A
+
+define i4 @or_or_xor_inner_or_outer_or_commuted(i4 %A, i4 %B) {
+; CHECK-LABEL: @or_or_xor_inner_or_outer_or_commuted(
+; CHECK-NEXT:    [[I1:%.*]] = or i4 [[B:%.*]], [[A:%.*]]
+; CHECK-NEXT:    ret i4 [[I1]]
+;
+  %i1 = or i4 %B, %A
+  %i2 = xor i4 %A, %B
+  %i3 = or i4 %i2, %i1
+  ret i4 %i3
+}
+
 define i32 @shifted_all_ones(i32 %shamt) {
 ; CHECK-LABEL: @shifted_all_ones(
 ; CHECK-NEXT:    ret i32 -1
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2265,6 +2265,19 @@
        match(Op0, m_c_Xor(m_Not(m_Specific(A)), m_Specific(B)))))
     return Op0;
 
+  // (A | B) | (A ^ B) --> A | B
+  // (B | A) | (A ^ B) --> B | A
+  if (match(Op1, m_Xor(m_Value(A), m_Value(B))) &&
+      match(Op0, m_c_Or(m_Specific(A), m_Specific(B))))
+    return Op0;
+
+  // Commute the outer 'or' operands.
+  // (A ^ B) | (A | B) --> A | B
+  // (A ^ B) | (B | A) --> B | A
+  if (match(Op0, m_Xor(m_Value(A), m_Value(B))) &&
+      match(Op1, m_c_Or(m_Specific(A), m_Specific(B))))
+    return Op1;
+
   // (~A & B) | ~(A | B) --> ~A
   // (~A & B) | ~(B | A) --> ~A
   // (B & ~A) | ~(A | B) --> ~A


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