[PATCH] D34498: [InstCombine] Add one use checks to or/and->xnor folding

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.

If the components of the and/or have multiple uses this transform creates an additional instruction.

This patch makes sure we remove one of the components.


https://reviews.llvm.org/D34498

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  test/Transforms/InstCombine/and-or-not.ll


Index: test/Transforms/InstCombine/and-or-not.ll
===================================================================
--- test/Transforms/InstCombine/and-or-not.ll
+++ test/Transforms/InstCombine/and-or-not.ll
@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -instcombine -S | FileCheck %s
 
 ; PR1510
@@ -516,3 +517,52 @@
   ret i64 %and
 }
 
+; (~a | b) & (~b | a) --> ~(a ^ b)
+; TODO: this increases instrunction count if the pieces have additional users
+define i32 @and_to_nxor_multiuse(float %fa, float %fb) {
+; CHECK-LABEL: @and_to_nxor_multiuse(
+; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
+; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
+; CHECK-NEXT:    [[NOTA:%.*]] = xor i32 [[A]], -1
+; CHECK-NEXT:    [[NOTB:%.*]] = xor i32 [[B]], -1
+; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[NOTA]], [[B]]
+; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[NOTB]], [[A]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B]], [[A]]
+; CHECK-NEXT:    [[AND:%.*]] = xor i32 [[TMP1]], -1
+; CHECK-NEXT:    [[MUL1:%.*]] = mul i32 [[OR1]], [[OR2]]
+; CHECK-NEXT:    [[MUL2:%.*]] = mul i32 [[MUL1]], [[AND]]
+; CHECK-NEXT:    ret i32 [[MUL2]]
+;
+  %a = fptosi float %fa to i32
+  %b = fptosi float %fb to i32
+  %nota = xor i32 %a, -1
+  %notb = xor i32 %b, -1
+  %or1 = or i32 %nota, %b
+  %or2 = or i32 %notb, %a
+  %and = and i32 %or1, %or2
+  %mul1 = mul i32 %or1, %or2 ; here to increase the use count of the inputs to the and
+  %mul2 = mul i32 %mul1, %and
+  ret i32 %mul2
+}
+
+; (a & b) | ~(a | b) --> ~(a ^ b)
+; TODO: this increases instrunction count if the pieces have additional users
+define i32 @or_to_nxor_multiuse(i32 %a, i32 %b) {
+; CHECK-LABEL: @or_to_nxor_multiuse(
+; CHECK-NEXT:    [[AND:%.*]] = and i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[OR:%.*]] = or i32 [[A]], [[B]]
+; CHECK-NEXT:    [[NOTOR:%.*]] = xor i32 [[OR]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[OR2:%.*]] = xor i32 [[TMP1]], -1
+; CHECK-NEXT:    [[MUL1:%.*]] = mul i32 [[AND]], [[NOTOR]]
+; CHECK-NEXT:    [[MUL2:%.*]] = mul i32 [[MUL1]], [[OR2]]
+; CHECK-NEXT:    ret i32 [[MUL2]]
+;
+  %and = and i32 %a, %b
+  %or = or i32 %a, %b
+  %notor = xor i32 %or, -1
+  %or2 = or i32 %and, %notor
+  %mul1 = mul i32 %and, %notor ; here to increase the use count of the inputs to the or
+  %mul2 = mul i32 %mul1, %or2
+  ret i32 %mul2
+}
Index: lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1239,9 +1239,10 @@
   // (A | ~B) & (B | ~A) --> ~(A ^ B)
   // (~B | A) & (~A | B) --> ~(A ^ B)
   // (~B | A) & (B | ~A) --> ~(A ^ B)
-  if (match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) &&
-      match(Op1, m_c_Or(m_Not(m_Specific(A)), m_Specific(B))))
-    return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
+  if (Op0->hasOneUse() || Op1->hasOneUse())
+    if (match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) &&
+        match(Op1, m_c_Or(m_Not(m_Specific(A)), m_Specific(B))))
+      return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
 
   return nullptr;
 }
@@ -1256,9 +1257,10 @@
   // Operand complexity canonicalization guarantees that the 'and' is Op0.
   // (A & B) | ~(A | B) --> ~(A ^ B)
   // (A & B) | ~(B | A) --> ~(A ^ B)
-  if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
-      match(Op1, m_Not(m_c_Or(m_Specific(A), m_Specific(B)))))
-    return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
+  if (Op0->hasOneUse() || Op1->hasOneUse())
+    if (match(Op0, m_And(m_Value(A), m_Value(B))) &&
+        match(Op1, m_Not(m_c_Or(m_Specific(A), m_Specific(B)))))
+      return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
 
   // (A & ~B) | (~A & B) --> A ^ B
   // (A & ~B) | (B & ~A) --> A ^ B


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