[llvm] 4b30076 - [InstSimplify] add logic fold for 'or'

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2021-11-30T14:08:54-05:00
New Revision: 4b30076f16fc55891da8952bda3f2d81dbeec5a5

URL: https://github.com/llvm/llvm-project/commit/4b30076f16fc55891da8952bda3f2d81dbeec5a5
DIFF: https://github.com/llvm/llvm-project/commit/4b30076f16fc55891da8952bda3f2d81dbeec5a5.diff

LOG: [InstSimplify] add logic fold for 'or'

https://alive2.llvm.org/ce/z/4PaPDy

There's a related fold where the inner 'or' is replaced by 'and',
but that needs to be more careful about matching a 'not'.

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 1f568ad6e839..9eb1ccd823de 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -2220,6 +2220,12 @@ static Value *simplifyOrLogic(Value *X, Value *Y) {
       match(Y, m_c_Or(m_Specific(A), m_Specific(B))))
     return Y;
 
+  // ~(A ^ B) | (A | B) --> -1
+  // ~(A ^ B) | (B | A) --> -1
+  if (match(X, m_Not(m_Xor(m_Value(A), m_Value(B)))) &&
+      match(Y, m_c_Or(m_Specific(A), m_Specific(B))))
+    return ConstantInt::getAllOnesValue(Ty);
+
   return nullptr;
 }
 

diff  --git a/llvm/test/Transforms/InstSimplify/or.ll b/llvm/test/Transforms/InstSimplify/or.ll
index 1d9d741fef2b..e73f6d273dc1 100644
--- a/llvm/test/Transforms/InstSimplify/or.ll
+++ b/llvm/test/Transforms/InstSimplify/or.ll
@@ -748,13 +748,11 @@ define <2 x i4> @or_nxor_and_undef_elt(<2 x i4> %a, <2 x i4> %b) {
   ret <2 x i4> %r
 }
 
+; ~(A ^ B) | (A | B) --> -1
+
 define i4 @or_nxor_or_commute0(i4 %a, i4 %b) {
 ; CHECK-LABEL: @or_nxor_or_commute0(
-; CHECK-NEXT:    [[OR:%.*]] = or i4 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i4 [[A]], [[B]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor i4 [[XOR]], -1
-; CHECK-NEXT:    [[R:%.*]] = or i4 [[NOT]], [[OR]]
-; CHECK-NEXT:    ret i4 [[R]]
+; CHECK-NEXT:    ret i4 -1
 ;
   %or = or i4 %a, %b
   %xor = xor i4 %a, %b
@@ -765,11 +763,7 @@ define i4 @or_nxor_or_commute0(i4 %a, i4 %b) {
 
 define <2 x i4> @or_nxor_or_commute1(<2 x i4> %a, <2 x i4> %b) {
 ; CHECK-LABEL: @or_nxor_or_commute1(
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i4> [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <2 x i4> [[A]], [[B]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor <2 x i4> [[XOR]], <i4 -1, i4 -1>
-; CHECK-NEXT:    [[R:%.*]] = or <2 x i4> [[OR]], [[NOT]]
-; CHECK-NEXT:    ret <2 x i4> [[R]]
+; CHECK-NEXT:    ret <2 x i4> <i4 -1, i4 -1>
 ;
   %or = or <2 x i4> %a, %b
   %xor = xor <2 x i4> %a, %b
@@ -780,11 +774,7 @@ define <2 x i4> @or_nxor_or_commute1(<2 x i4> %a, <2 x i4> %b) {
 
 define i74 @or_nxor_or_commute2(i74 %a, i74 %b) {
 ; CHECK-LABEL: @or_nxor_or_commute2(
-; CHECK-NEXT:    [[OR:%.*]] = or i74 [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor i74 [[A]], [[B]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor i74 [[XOR]], -1
-; CHECK-NEXT:    [[R:%.*]] = or i74 [[NOT]], [[OR]]
-; CHECK-NEXT:    ret i74 [[R]]
+; CHECK-NEXT:    ret i74 -1
 ;
   %or = or i74 %b, %a
   %xor = xor i74 %a, %b
@@ -795,11 +785,7 @@ define i74 @or_nxor_or_commute2(i74 %a, i74 %b) {
 
 define <2 x i4> @or_nxor_or_commute3(<2 x i4> %a, <2 x i4> %b) {
 ; CHECK-LABEL: @or_nxor_or_commute3(
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i4> [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <2 x i4> [[A]], [[B]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor <2 x i4> [[XOR]], <i4 -1, i4 -1>
-; CHECK-NEXT:    [[R:%.*]] = or <2 x i4> [[OR]], [[NOT]]
-; CHECK-NEXT:    ret <2 x i4> [[R]]
+; CHECK-NEXT:    ret <2 x i4> <i4 -1, i4 -1>
 ;
   %or = or <2 x i4> %b, %a
   %xor = xor <2 x i4> %a, %b
@@ -808,6 +794,8 @@ define <2 x i4> @or_nxor_or_commute3(<2 x i4> %a, <2 x i4> %b) {
   ret <2 x i4> %r
 }
 
+; negative test - must have common operands
+
 define i4 @or_nxor_or_wrong_val1(i4 %a, i4 %b, i4 %c) {
 ; CHECK-LABEL: @or_nxor_or_wrong_val1(
 ; CHECK-NEXT:    [[OR:%.*]] = or i4 [[A:%.*]], [[C:%.*]]
@@ -823,6 +811,8 @@ define i4 @or_nxor_or_wrong_val1(i4 %a, i4 %b, i4 %c) {
   ret i4 %r
 }
 
+; negative test - must have common operands
+
 define i4 @or_nxor_or_wrong_val2(i4 %a, i4 %b, i4 %c) {
 ; CHECK-LABEL: @or_nxor_or_wrong_val2(
 ; CHECK-NEXT:    [[OR:%.*]] = or i4 [[C:%.*]], [[B:%.*]]
@@ -838,13 +828,11 @@ define i4 @or_nxor_or_wrong_val2(i4 %a, i4 %b, i4 %c) {
   ret i4 %r
 }
 
+; undef in 'not' is allowed
+
 define <2 x i4> @or_nxor_or_undef_elt(<2 x i4> %a, <2 x i4> %b) {
 ; CHECK-LABEL: @or_nxor_or_undef_elt(
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i4> [[B:%.*]], [[A:%.*]]
-; CHECK-NEXT:    [[XOR:%.*]] = xor <2 x i4> [[A]], [[B]]
-; CHECK-NEXT:    [[NOT:%.*]] = xor <2 x i4> [[XOR]], <i4 -1, i4 undef>
-; CHECK-NEXT:    [[R:%.*]] = or <2 x i4> [[OR]], [[NOT]]
-; CHECK-NEXT:    ret <2 x i4> [[R]]
+; CHECK-NEXT:    ret <2 x i4> <i4 -1, i4 -1>
 ;
   %or = or <2 x i4> %b, %a
   %xor = xor <2 x i4> %a, %b