[llvm] e1bd759 - [InstCombine] allow more matches for logical-ands --> select

[Sanjay Patel via llvm-commits]

Author: Sanjay Patel
Date: 2022-10-22T08:15:50-04:00
New Revision: e1bd759ea56710a9e7b9a4068af0ee95f1ad217e

URL: https://github.com/llvm/llvm-project/commit/e1bd759ea56710a9e7b9a4068af0ee95f1ad217e
DIFF: https://github.com/llvm/llvm-project/commit/e1bd759ea56710a9e7b9a4068af0ee95f1ad217e.diff

LOG: [InstCombine] allow more matches for logical-ands --> select

This allows patterns with real 'and' instructions because
those are safe to transform:
https://alive2.llvm.org/ce/z/7-U_Ak

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
    llvm/test/Transforms/InstCombine/select-safe-transforms.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 4e0ca608837ae..503d394c3f3c4 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -2852,18 +2852,21 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
 
       // (C && A) || (!C && B) --> sel C, A, B
       // (A && C) || (!C && B) --> sel C, A, B
-      if (match(FalseVal, m_LogicalAnd(m_Not(m_Value(C)), m_Value(B))) &&
-          match(CondVal, m_c_LogicalAnd(m_Specific(C), m_Value(A))))
-        return SelectInst::Create(C, A, B);
-
       // (C && A) || (B && !C) --> sel C, A, B
-      // TODO: (A && C) || (B && !C) is safe to transform with real 'and' ops.
-      if (match(FalseVal, m_LogicalAnd(m_Value(B), m_Not(m_Value(C)))) &&
-          match(CondVal, m_LogicalAnd(m_Specific(C), m_Value(A))))
-        return SelectInst::Create(C, A, B);
+      // (A && C) || (B && !C) --> sel C, A, B (only with real 'and' ops)
+      if (match(FalseVal, m_c_LogicalAnd(m_Not(m_Value(C)), m_Value(B))) &&
+          match(CondVal, m_c_LogicalAnd(m_Specific(C), m_Value(A)))) {
+        auto *SelCond = dyn_cast<SelectInst>(CondVal);
+        auto *SelFVal = dyn_cast<SelectInst>(FalseVal);
+        if (!SelCond || !SelFVal ||
+            !match(SelFVal->getTrueValue(),
+                   m_Not(m_Specific(SelCond->getTrueValue()))))
+          return SelectInst::Create(C, A, B);
+      }
 
       // (!C && A) || (C && B) --> sel C, B, A
       // (!C && A) || (B && C) --> sel C, B, A
+      // TODO: Allow more commutes as with the previous fold.
       if (match(CondVal, m_LogicalAnd(m_Not(m_Value(C)), m_Value(A))) &&
           match(FalseVal, m_c_LogicalAnd(m_Specific(C), m_Value(B))))
         return SelectInst::Create(C, B, A);

diff  --git a/llvm/test/Transforms/InstCombine/select-safe-transforms.ll b/llvm/test/Transforms/InstCombine/select-safe-transforms.ll
index b0b8108ac599a..4ac1bd5d7eeb0 100644
--- a/llvm/test/Transforms/InstCombine/select-safe-transforms.ll
+++ b/llvm/test/Transforms/InstCombine/select-safe-transforms.ll
@@ -529,6 +529,8 @@ define i1 @bools2_logical_commute2_and1_and2(i1 %a, i1 %c) {
   ret i1 %or
 }
 
+; This is not safe to transform if 'c' could be poison.
+
 define i1 @bools2_logical_commute3(i1 %a, i1 %b, i1 %c) {
 ; CHECK-LABEL: @bools2_logical_commute3(
 ; CHECK-NEXT:    [[NOT:%.*]] = xor i1 [[C:%.*]], true
@@ -546,10 +548,7 @@ define i1 @bools2_logical_commute3(i1 %a, i1 %b, i1 %c) {
 
 define i1 @bools2_logical_commute3_and1(i1 %a, i1 %b, i1 %c) {
 ; CHECK-LABEL: @bools2_logical_commute3_and1(
-; CHECK-NEXT:    [[NOT:%.*]] = xor i1 [[C:%.*]], true
-; CHECK-NEXT:    [[AND1:%.*]] = and i1 [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[AND2:%.*]] = select i1 [[B:%.*]], i1 [[NOT]], i1 false
-; CHECK-NEXT:    [[OR:%.*]] = select i1 [[AND1]], i1 true, i1 [[AND2]]
+; CHECK-NEXT:    [[OR:%.*]] = select i1 [[C:%.*]], i1 [[A:%.*]], i1 [[B:%.*]]
 ; CHECK-NEXT:    ret i1 [[OR]]
 ;
   %not = xor i1 %c, -1
@@ -562,10 +561,7 @@ define i1 @bools2_logical_commute3_and1(i1 %a, i1 %b, i1 %c) {
 define i1 @bools2_logical_commute3_and2(i1 %a, i1 %c) {
 ; CHECK-LABEL: @bools2_logical_commute3_and2(
 ; CHECK-NEXT:    [[B:%.*]] = call i1 @gen1()
-; CHECK-NEXT:    [[NOT:%.*]] = xor i1 [[C:%.*]], true
-; CHECK-NEXT:    [[AND1:%.*]] = select i1 [[A:%.*]], i1 [[C]], i1 false
-; CHECK-NEXT:    [[AND2:%.*]] = and i1 [[B]], [[NOT]]
-; CHECK-NEXT:    [[OR:%.*]] = select i1 [[AND1]], i1 true, i1 [[AND2]]
+; CHECK-NEXT:    [[OR:%.*]] = select i1 [[C:%.*]], i1 [[A:%.*]], i1 [[B]]
 ; CHECK-NEXT:    ret i1 [[OR]]
 ;
   %b = call i1 @gen1()
@@ -579,10 +575,7 @@ define i1 @bools2_logical_commute3_and2(i1 %a, i1 %c) {
 define i1 @bools2_logical_commute3_and1_and2(i1 %a, i1 %c) {
 ; CHECK-LABEL: @bools2_logical_commute3_and1_and2(
 ; CHECK-NEXT:    [[B:%.*]] = call i1 @gen1()
-; CHECK-NEXT:    [[NOT:%.*]] = xor i1 [[C:%.*]], true
-; CHECK-NEXT:    [[AND1:%.*]] = and i1 [[A:%.*]], [[C]]
-; CHECK-NEXT:    [[AND2:%.*]] = and i1 [[B]], [[NOT]]
-; CHECK-NEXT:    [[OR:%.*]] = select i1 [[AND1]], i1 true, i1 [[AND2]]
+; CHECK-NEXT:    [[OR:%.*]] = select i1 [[C:%.*]], i1 [[A:%.*]], i1 [[B]]
 ; CHECK-NEXT:    ret i1 [[OR]]
 ;
   %b = call i1 @gen1()