[InstCombine] Use m_NotForbidPoison when folding (X u< Y) ? -1 : (~X + Y) --> uadd.sat(~X, Y)

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -1051,7 +1051,7 @@ static Value *canonicalizeSaturatedAdd(ICmpInst *Cmp, Value *TVal, Value *FVal,
   // Strictness of the comparison is irrelevant.
   X = Cmp0;
   Y = Cmp1;
-  if (match(FVal, m_c_Add(m_Not(m_Specific(X)), m_Specific(Y)))) {
+  if (match(FVal, m_c_Add(m_NotForbidPoison(m_Specific(X)), m_Specific(Y)))) {
     // (X u< Y) ? -1 : (~X + Y) --> uadd.sat(~X, Y)
     // (X u< Y) ? -1 : (Y + ~X) --> uadd.sat(Y, ~X)
     BinaryOperator *BO = cast<BinaryOperator>(FVal);

llvm/test/Transforms/InstCombine/saturating-add-sub.ll

@@ -1893,7 +1893,9 @@ define <2 x i32> @uadd_sat_not_ugt_commute_add(<2 x i32> %x, <2 x i32> %yp) {
 define <2 x i32> @uadd_sat_not_ugt_commute_add_partial_poison(<2 x i32> %x, <2 x i32> %yp) {
 ; CHECK-LABEL: @uadd_sat_not_ugt_commute_add_partial_poison(
 ; CHECK-NEXT:    [[NOTX:%.*]] = xor <2 x i32> [[X:%.*]], <i32 -1, i32 poison>
-; CHECK-NEXT:    [[R:%.*]] = call <2 x i32> @llvm.uadd.sat.v2i32(<2 x i32> [[YP:%.*]], <2 x i32> [[NOTX]])
+; CHECK-NEXT:    [[A:%.*]] = add nuw <2 x i32> [[YP:%.*]], [[NOTX]]
+; CHECK-NEXT:    [[C:%.*]] = icmp ugt <2 x i32> [[YP]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[C]], <2 x i32> <i32 -1, i32 -1>, <2 x i32> [[A]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %notx = xor <2 x i32> %x, <i32 -1, i32 poison>