if ((SPF == SPF_SMAX || SPF == SPF_UMAX) &&
IsFreeToInvert(LHS, LHS->hasNUses(2)) &&
IsFreeToInvert(RHS, RHS->hasNUses(2))) {
- // This transform adds a not operation, and that extra cost needs to be
- // justified. We look for simplifications that will result from applying
- // this rule:
- bool Profitable =
- (LHS->hasNUses(2) && match(LHS, m_Not(m_Value()))) ||
- (RHS->hasNUses(2) && match(RHS, m_Not(m_Value()))) ||
+ // For this transform to be profitable, we need to eliminate at least two
+ // 'not' instructions if we're going to add one 'not' instruction.
+ int NumberOfNots =
+ (LHS->hasNUses(2) && match(LHS, m_Not(m_Value()))) +
+ (RHS->hasNUses(2) && match(RHS, m_Not(m_Value()))) +
(SI.hasOneUse() && match(*SI.user_begin(), m_Not(m_Value())));
- if (Profitable) {
+ if (NumberOfNots >= 2) {
Value *NewLHS = Builder->CreateNot(LHS);
Value *NewRHS = Builder->CreateNot(RHS);
Value *NewCmp = SPF == SPF_SMAX
ret i32 %min
}
+; Don't increase the critical path by moving the 'not' op after the 'select'.
+
define i32 @compute_min_arithmetic(i32 %x, i32 %y) {
; CHECK-LABEL: @compute_min_arithmetic(
-; CHECK-NEXT: [[TMP1:%.*]] = add i32 %x, -4
-; CHECK-NEXT: [[TMP2:%.*]] = icmp slt i32 [[TMP1]], %y
-; CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[TMP1]], i32 %y
-; CHECK-NEXT: [[TMP4:%.*]] = xor i32 [[TMP3]], -1
-; CHECK-NEXT: ret i32 [[TMP4]]
+; CHECK-NEXT: [[NOT_VALUE:%.*]] = sub i32 3, %x
+; CHECK-NEXT: [[NOT_Y:%.*]] = xor i32 %y, -1
+; CHECK-NEXT: [[CMP:%.*]] = icmp sgt i32 [[NOT_VALUE]], [[NOT_Y]]
+; CHECK-NEXT: [[NOT_MIN:%.*]] = select i1 [[CMP]], i32 [[NOT_VALUE]], i32 [[NOT_Y]]
+; CHECK-NEXT: ret i32 [[NOT_MIN]]
;
%not_value = sub i32 3, %x
%not_y = sub i32 -1, %y