[EarlyCSE] recognize swapped variants of abs/nabs as equivalent

Extends https://reviews.llvm.org/rL320640

Differential Revision: https://reviews.llvm.org/D41136

llvm-svn: 320653

llvm/lib/Transforms/Scalar/EarlyCSE.cpp

@@ -143,14 +143,16 @@ unsigned DenseMapInfo<SimpleValue>::getHashValue(SimpleValue Val) {
     return hash_combine(Inst->getOpcode(), Pred, LHS, RHS);
   }
 
-  // Hash min/max (cmp + select) to allow for commuted operands, non-canonical
-  // compare predicate (eg, the compare for smin may use 'sgt' rather than
-  // 'slt'), and non-canonical operands in the compare.
+  // Hash min/max/abs (cmp + select) to allow for commuted operands.
+  // Min/max may also have non-canonical compare predicate (eg, the compare for
+  // smin may use 'sgt' rather than 'slt'), and non-canonical operands in the
+  // compare.
   Value *A, *B;
   SelectPatternFlavor SPF = matchSelectPattern(Inst, A, B).Flavor;
-  // TODO: We should also detect abs and FP min/max.
+  // TODO: We should also detect FP min/max.
   if (SPF == SPF_SMIN || SPF == SPF_SMAX ||
-      SPF == SPF_UMIN || SPF == SPF_UMAX) {
+      SPF == SPF_UMIN || SPF == SPF_UMAX ||
+      SPF == SPF_ABS || SPF == SPF_NABS) {
     if (A > B)
       std::swap(A, B);
     return hash_combine(Inst->getOpcode(), SPF, A, B);
@@ -214,13 +216,14 @@ bool DenseMapInfo<SimpleValue>::isEqual(SimpleValue LHS, SimpleValue RHS) {
            LHSCmp->getSwappedPredicate() == RHSCmp->getPredicate();
   }
 
-  // Min/max can occur with commuted operands, non-canonical predicates, and/or
-  // non-canonical operands.
+  // Min/max/abs can occur with commuted operands, non-canonical predicates,
+  // and/or non-canonical operands.
   Value *LHSA, *LHSB;
   SelectPatternFlavor LSPF = matchSelectPattern(LHSI, LHSA, LHSB).Flavor;
-  // TODO: We should also detect abs and FP min/max.
+  // TODO: We should also detect FP min/max.
   if (LSPF == SPF_SMIN || LSPF == SPF_SMAX ||
-      LSPF == SPF_UMIN || LSPF == SPF_UMAX) {
+      LSPF == SPF_UMIN || LSPF == SPF_UMAX ||
+      LSPF == SPF_ABS || LSPF == SPF_NABS) {
     Value *RHSA, *RHSB;
     SelectPatternFlavor RSPF = matchSelectPattern(RHSI, RHSA, RHSB).Flavor;
     return (LSPF == RSPF && ((LHSA == RHSA && LHSB == RHSB) ||

llvm/test/Transforms/EarlyCSE/commute.ll

@@ -224,9 +224,7 @@ define i8 @abs_swapped(i8 %a) {
 ; CHECK-NEXT:    [[CMP1:%.*]] = icmp sgt i8 %a, 0
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp slt i8 %a, 0
 ; CHECK-NEXT:    [[M1:%.*]] = select i1 [[CMP1]], i8 %a, i8 [[NEG]]
-; CHECK-NEXT:    [[M2:%.*]] = select i1 [[CMP2]], i8 [[NEG]], i8 %a
-; CHECK-NEXT:    [[R:%.*]] = or i8 [[M2]], [[M1]]
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 [[M1]]
 ;
   %neg = sub i8 0, %a
   %cmp1 = icmp sgt i8 %a, 0
@@ -243,9 +241,7 @@ define i8 @nabs_swapped(i8 %a) {
 ; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i8 %a, 0
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp sgt i8 %a, 0
 ; CHECK-NEXT:    [[M1:%.*]] = select i1 [[CMP1]], i8 %a, i8 [[NEG]]
-; CHECK-NEXT:    [[M2:%.*]] = select i1 [[CMP2]], i8 [[NEG]], i8 %a
-; CHECK-NEXT:    [[R:%.*]] = xor i8 [[M2]], [[M1]]
-; CHECK-NEXT:    ret i8 [[R]]
+; CHECK-NEXT:    ret i8 0
 ;
   %neg = sub i8 0, %a
   %cmp1 = icmp slt i8 %a, 0