[InstCombine] Fold (a | b) ^ (~a | ~b) --> ~(a ^ b) and (a & b) ^ (~a & ~b) --> ~(a ^ b)

Summary:
I came across this while thinking about what would happen if one of the operands in this xor pattern was itself a inverted (A & ~B) ^ (~A & B)-> (A^B).

The patterns here assume that the (~a | ~b) will be demorganed to ~(a & b) first. Though I wonder if there's a multiple use case that would prevent the demorgan.

Reviewers: spatel

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34870

llvm-svn: 306967

2 files changed, 16 insertions, 32 deletions

diff --git a/llvm/test/Transforms/InstCombine/and-or-not.ll b/llvm/test/Transforms/InstCombine/and-or-not.ll
index 1baecb4a13a..04f7be01eaf 100644
--- a/llvm/test/Transforms/InstCombine/and-or-not.ll
+++ b/llvm/test/Transforms/InstCombine/and-or-not.ll
@@ -570,10 +570,8 @@ define i32 @xor_to_xnor1(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xnor1(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[A]], [[B]]
-; CHECK-NEXT:    [[OR2_DEMORGAN:%.*]] = and i32 [[A]], [[B]]
-; CHECK-NEXT:    [[OR2:%.*]] = xor i32 [[OR2_DEMORGAN]], -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR1]], [[OR2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
@@ -591,10 +589,8 @@ define i32 @xor_to_xnor2(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xnor2(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[A]], [[B]]
-; CHECK-NEXT:    [[OR2_DEMORGAN:%.*]] = and i32 [[B]], [[A]]
-; CHECK-NEXT:    [[OR2:%.*]] = xor i32 [[OR2_DEMORGAN]], -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR1]], [[OR2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
@@ -612,10 +608,8 @@ define i32 @xor_to_xnor3(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xnor3(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[OR1_DEMORGAN:%.*]] = and i32 [[A]], [[B]]
-; CHECK-NEXT:    [[OR1:%.*]] = xor i32 [[OR1_DEMORGAN]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[A]], [[B]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR2]], [[OR1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
@@ -633,10 +627,8 @@ define i32 @xor_to_xnor4(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xnor4(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[OR1_DEMORGAN:%.*]] = and i32 [[A]], [[B]]
-; CHECK-NEXT:    [[OR1:%.*]] = xor i32 [[OR1_DEMORGAN]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[B]], [[A]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR2]], [[OR1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[B]], [[A]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
diff --git a/llvm/test/Transforms/InstCombine/or-xor.ll b/llvm/test/Transforms/InstCombine/or-xor.ll
index 2164f0df8d2..947971c6c83 100644
--- a/llvm/test/Transforms/InstCombine/or-xor.ll
+++ b/llvm/test/Transforms/InstCombine/or-xor.ll
@@ -348,10 +348,8 @@ define i8 @test18(i8 %A, i8 %B) {
 ; ((x | y) ^ (~x | ~y)) -> ~(x ^ y)
 define i32 @test19(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test19(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[OR2_DEMORGAN:%.*]] = and i32 [[X]], [[Y]]
-; CHECK-NEXT:    [[OR2:%.*]] = xor i32 [[OR2_DEMORGAN]], -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR1]], [[OR2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
@@ -365,10 +363,8 @@ define i32 @test19(i32 %x, i32 %y) {
 ; ((x | y) ^ (~y | ~x)) -> ~(x ^ y)
 define i32 @test20(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test20(
-; CHECK-NEXT:    [[OR1:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[OR2_DEMORGAN:%.*]] = and i32 [[Y]], [[X]]
-; CHECK-NEXT:    [[OR2:%.*]] = xor i32 [[OR2_DEMORGAN]], -1
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR1]], [[OR2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
@@ -382,10 +378,8 @@ define i32 @test20(i32 %x, i32 %y) {
 ; ((~x | ~y) ^ (x | y)) -> ~(x ^ y)
 define i32 @test21(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test21(
-; CHECK-NEXT:    [[OR1_DEMORGAN:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[OR1:%.*]] = xor i32 [[OR1_DEMORGAN]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[X]], [[Y]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR2]], [[OR1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
@@ -399,10 +393,8 @@ define i32 @test21(i32 %x, i32 %y) {
 ; ((~x | ~y) ^ (y | x)) -> ~(x ^ y)
 define i32 @test22(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test22(
-; CHECK-NEXT:    [[OR1_DEMORGAN:%.*]] = and i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[OR1:%.*]] = xor i32 [[OR1_DEMORGAN]], -1
-; CHECK-NEXT:    [[OR2:%.*]] = or i32 [[Y]], [[X]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[OR2]], [[OR1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = xor i32 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[TMP1]], -1
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1