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[InstCombine] update code/test comments; NFC 

Follow-up for post-commit suggestion on:
28afaed691

The comments were partly copied from the original
code, but not updated to match the new code.
This commit is contained in:
Sanjay Patel 2021-09-11 10:52:00 -04:00
parent f5806830e0
commit 75e8eb2b10
2 changed files with 10 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
View File

@ -2057,11 +2057,11 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
return BinaryOperator::CreateAnd(
Op0, Builder.CreateNot(Y, Y->getName() + ".not"));
// ~X - Min/Max(~X, O) -> Max/Min(X, ~O) - X
// ~X - Min/Max(O, ~X) -> Max/Min(X, ~O) - X
// Min/Max(~X, O) - ~X -> A - Max/Min(X, ~O)
// Min/Max(O, ~X) - ~X -> A - Max/Min(X, ~O)
// So long as O here is freely invertible, this will be neutral or a win.
// ~X - Min/Max(~X, Y) -> ~Min/Max(X, ~Y) - X
// ~X - Min/Max(Y, ~X) -> ~Min/Max(X, ~Y) - X
// Min/Max(~X, Y) - ~X -> X - ~Min/Max(X, ~Y)
// Min/Max(Y, ~X) - ~X -> X - ~Min/Max(X, ~Y)
// As long as Y is freely invertible, this will be neutral or a win.
// Note: We don't generate the inverse max/min, just create the 'not' of
// it and let other folds do the rest.
if (match(Op0, m_Not(m_Value(X))) &&
@ -2094,7 +2094,7 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
match(NotA, m_Not(m_Value(A))) && (NotA == LHS || NotA == RHS)) {
if (NotA == LHS)
std::swap(LHS, RHS);
// LHS is now O above and expected to have at least 2 uses (the min/max)
// LHS is now Y above and expected to have at least 2 uses (the min/max)
// NotA is expected to have 2 uses from the min/max and 1 from the sub.
if (isFreeToInvert(LHS, !LHS->hasNUsesOrMore(3)) &&
!NotA->hasNUsesOrMore(4)) {

8
llvm/test/Transforms/InstCombine/sub-minmax.ll
View File

@ -394,10 +394,10 @@ define void @umin3_not_all_ops_extra_uses_invert_subs(i8 %x, i8 %y, i8 %z) {
}
; Handle this pattern with extra uses because it shows up in benchmarks.
; ~X - Min/Max(~X, O) -> Max/Min(X, ~O) - X
; ~X - Min/Max(O, ~X) -> Max/Min(X, ~O) - X
; Min/Max(~X, O) - ~X -> A - Max/Min(X, ~O)
; Min/Max(O, ~X) - ~X -> A - Max/Min(X, ~O)
; ~X - Min/Max(~X, Y) -> ~Min/Max(X, ~Y) - X
; ~X - Min/Max(Y, ~X) -> ~Min/Max(X, ~Y) - X
; Min/Max(~X, Y) - ~X -> X - ~Min/Max(X, ~Y)
; Min/Max(Y, ~X) - ~X -> X - ~Min/Max(X, ~Y)
define i8 @umin_not_sub_intrinsic_commute0(i8 %x, i8 %y) {
; CHECK-LABEL: @umin_not_sub_intrinsic_commute0(