On 16/08/18 23:12, Luc Van Oostenryck wrote:
> In an expression like this, if the inner constant (K) and
> the mask are disjoint ((K & M) == 0), then the OR with
> the constant is unneeded and can be optimized away since
> the constant will be 'cleared' by the mask, giving: OP(x, K)
>
> For example, code like:
> int foo(int x)
> {
> return (x | 0xfffff000) & 0xfff;
> }
Sorry to be dense, but I'm lost again. The above example implies
to me that OP == &, C == 0xfffff000, K == 0xfff. So what is M?
Yes ((K & C) == 0) leaving OP(x, K) => (x & 0xfff).
Again where is M coming from?
>
> is now optimized into:
> foo:
> and.32 %r3 <- %arg1, $0xfff
> ret.32 %r3
>
> while previously the OR mask was not optimized away:
> foo:
> or.32 %r2 <- %arg1, $0xfffff000
> and.32 %r3 <- %r2, $0xfff
> ret.32 %r3
>
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
> ---
> simplify.c | 9 +++++++++
> validation/optim/and-or-bf0.c | 1 -
> validation/optim/and-or-constant0.c | 1 -
> 3 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/simplify.c b/simplify.c
> index e985a1db7..edc84e3ba 100644
> --- a/simplify.c
> +++ b/simplify.c
> @@ -609,6 +609,15 @@ static int simplify_mask_or(struct instruction *insn, unsigned long long mask, s
> if (src2->type == PSEUDO_REG) {
> if ((rc = simplify_mask_or_and(insn, mask, src2, src1)))
> return rc;
> + } else if (src2->type == PSEUDO_VAL) {
> + unsigned long long oval = src2->value;
> + unsigned long long nval = oval & mask;
> + // Try to simplify:
> + // OP(OR(x, C), K)
> + if (nval == 0) {
> + // if (C & M) == 0: OR(x, C) -> x
Again (C & M) ?
confused again! ;-)
ATB,
Ramsay Jones
> + return replace_pseudo(insn, &insn->src1, src1);
> + }
> }
> return 0;
> }
> diff --git a/validation/optim/and-or-bf0.c b/validation/optim/and-or-bf0.c
> index a17ff82d3..cfaff4f20 100644
> --- a/validation/optim/and-or-bf0.c
> +++ b/validation/optim/and-or-bf0.c
> @@ -17,7 +17,6 @@ void bar(struct s *p, int a)
> /*
> * check-name: and-or-bf0
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-ignore
> * check-output-pattern(3): and\\.
> diff --git a/validation/optim/and-or-constant0.c b/validation/optim/and-or-constant0.c
> index e3ff0fa46..dcf440f33 100644
> --- a/validation/optim/and-or-constant0.c
> +++ b/validation/optim/and-or-constant0.c
> @@ -6,7 +6,6 @@ int foo(int x)
> /*
> * check-name: and-or-constant0
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-ignore
> * check-output-excludes: or\\.
>
