[InstCombine] Handle commuted patterns in foldSelectWithSRem

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -2823,9 +2823,9 @@ static Instruction *foldSelectWithSRem(SelectInst &SI, InstCombinerImpl &IC,
   // %cnd = icmp slt i32 %rem, 0
   // %add = add i32 %rem, %n
   // %sel = select i1 %cnd, i32 %add, i32 %rem
-  if (match(TrueVal, m_Add(m_Specific(RemRes), m_Value(Remainder))) &&
+  if (match(TrueVal, m_c_Add(m_Specific(RemRes), m_Value(Remainder))) &&
       match(RemRes, m_SRem(m_Value(Op), m_Specific(Remainder))) &&
-      IC.isKnownToBeAPowerOfTwo(Remainder, /*OrZero*/ true) &&
+      IC.isKnownToBeAPowerOfTwo(Remainder, /*OrZero=*/true) &&
       FalseVal == RemRes)
     return FoldToBitwiseAnd(Remainder);
 

llvm/test/Transforms/InstCombine/select-divrem.ll

@@ -324,11 +324,9 @@ define i8 @rem_euclid_non_const_pow2(i8 %0, i8 %1) {
 
 define i8 @rem_euclid_non_const_pow2_commuted(i8 %0, i8 %1) {
 ; CHECK-LABEL: @rem_euclid_non_const_pow2_commuted(
-; CHECK-NEXT:    [[POW2:%.*]] = shl nuw i8 1, [[TMP0:%.*]]
-; CHECK-NEXT:    [[REM:%.*]] = srem i8 [[TMP1:%.*]], [[POW2]]
-; CHECK-NEXT:    [[COND:%.*]] = icmp slt i8 [[REM]], 0
-; CHECK-NEXT:    [[ADD:%.*]] = select i1 [[COND]], i8 [[POW2]], i8 0
-; CHECK-NEXT:    [[SEL:%.*]] = add i8 [[REM]], [[ADD]]
+; CHECK-NEXT:    [[NOTMASK:%.*]] = shl nsw i8 -1, [[TMP0:%.*]]
+; CHECK-NEXT:    [[TMP3:%.*]] = xor i8 [[NOTMASK]], -1
+; CHECK-NEXT:    [[SEL:%.*]] = and i8 [[TMP1:%.*]], [[TMP3]]
 ; CHECK-NEXT:    ret i8 [[SEL]]
 ;
   %pow2 = shl i8 1, %0