On 16/08/18 23:12, Luc Van Oostenryck wrote:
> If the effective mask (C & M) is equal to the outer mask (M),
> then the OR operation is unneeded and can be replaced by M itself,
> giving: OP(M', K) with M' == (C & M)
>
> For example, code like:
> unsigned int foo(int x)
> {
> return (x | 7) & 2;
> }
C == 7, K == 2, OP == &, (C & K) == K. Hmm, so M == K?
ATB,
Ramsay Jones
>
> is now simplified into:
> foo:
> ret.32 $2
>
> which previously was not optimized
> foo:
> or.32 %r2 <- %arg1, $7
> and.32 %r3 <- %r2, $2
> ret.32 %r3
>
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
> ---
> simplify.c | 4 ++++
> validation/optim/and-or-constant1.c | 1 -
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/simplify.c b/simplify.c
> index edc84e3ba..755371002 100644
> --- a/simplify.c
> +++ b/simplify.c
> @@ -618,6 +618,10 @@ static int simplify_mask_or(struct instruction *insn, unsigned long long mask, s
> // if (C & M) == 0: OR(x, C) -> x
> return replace_pseudo(insn, &insn->src1, src1);
> }
> + if (nval == mask) {
> + // if (C & M) == M: OR(x, C) -> (C & M)
> + return replace_pseudo(insn, &insn->src1, value_pseudo(nval));
> + }
> }
> return 0;
> }
> diff --git a/validation/optim/and-or-constant1.c b/validation/optim/and-or-constant1.c
> index 3f1c90528..49823d5ca 100644
> --- a/validation/optim/and-or-constant1.c
> +++ b/validation/optim/and-or-constant1.c
> @@ -6,7 +6,6 @@ int foo(int x)
> /*
> * check-name: or-and-constant1
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-ignore
> * check-output-contains: ret\\..*\\$0xfff
>
