NewOps[0] == NewOps[1])
return NewOps[0];
+ // x - x -> 0. This is non-refining, because x is non-poison by assumption
+ // and this case never wraps, so nowrap flags can be ignored.
+ if (Opcode == Instruction::Sub && NewOps[0] == NewOps[1]) {
+ assert(NewOps[0] == RepOp && "Precondition for non-poison assumption");
+ return Constant::getNullValue(I->getType());
+ }
+
// If we are substituting an absorber constant into a binop and extra
// poison can't leak if we remove the select -- because both operands of
// the binop are based on the same value -- then it may be safe to replace
define i8 @select_sub_cmp(i8 %0, i8 %1) {
; CHECK-LABEL: @select_sub_cmp(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i8 [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw i8 [[TMP1]], [[TMP0]]
-; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP3]], i8 0, i8 [[TMP4]]
-; CHECK-NEXT: ret i8 [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw i8 [[TMP1:%.*]], [[TMP0:%.*]]
+; CHECK-NEXT: ret i8 [[TMP3]]
;
%3 = icmp eq i8 %1, %0
%4 = sub nsw i8 %1, %0
define <2 x i8> @select_sub_cmp_vec(<2 x i8> %0, <2 x i8> %1) {
; CHECK-LABEL: @select_sub_cmp_vec(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw <2 x i8> [[TMP1]], [[TMP0]]
-; CHECK-NEXT: [[TMP5:%.*]] = select <2 x i1> [[TMP3]], <2 x i8> zeroinitializer, <2 x i8> [[TMP4]]
-; CHECK-NEXT: ret <2 x i8> [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]]
+; CHECK-NEXT: ret <2 x i8> [[TMP3]]
;
%3 = icmp eq <2 x i8> %1, %0
%4 = sub nsw <2 x i8> %1, %0
define i8 @select_sub_cmp_swap(i8 %0, i8 %1) {
; CHECK-LABEL: @select_sub_cmp_swap(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq i8 [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw i8 [[TMP0]], [[TMP1]]
-; CHECK-NEXT: [[TMP5:%.*]] = select i1 [[TMP3]], i8 0, i8 [[TMP4]]
-; CHECK-NEXT: ret i8 [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw i8 [[TMP0:%.*]], [[TMP1:%.*]]
+; CHECK-NEXT: ret i8 [[TMP3]]
;
%3 = icmp eq i8 %1, %0
%4 = sub nsw i8 %0, %1
define <2 x i8> @select_sub_cmp_vec_swap(<2 x i8> %0, <2 x i8> %1) {
; CHECK-LABEL: @select_sub_cmp_vec_swap(
-; CHECK-NEXT: [[TMP3:%.*]] = icmp eq <2 x i8> [[TMP1:%.*]], [[TMP0:%.*]]
-; CHECK-NEXT: [[TMP4:%.*]] = sub nsw <2 x i8> [[TMP0]], [[TMP1]]
-; CHECK-NEXT: [[TMP5:%.*]] = select <2 x i1> [[TMP3]], <2 x i8> zeroinitializer, <2 x i8> [[TMP4]]
-; CHECK-NEXT: ret <2 x i8> [[TMP5]]
+; CHECK-NEXT: [[TMP3:%.*]] = sub nsw <2 x i8> [[TMP0:%.*]], [[TMP1:%.*]]
+; CHECK-NEXT: ret <2 x i8> [[TMP3]]
;
%3 = icmp eq <2 x i8> %1, %0
%4 = sub nsw <2 x i8> %0, %1