On 16/08/18 23:12, Luc Van Oostenryck wrote:
> Currently, in simplify_mask_or_and(), only the cases where
> (M' & M) == 0 or (M' & M) == M are simplified. However, if the
> effective mask (M' & M) is different than the original inner mask
> (M'), this inner mask can be replaced by the smaller effective one,
> giving: OP(((x & M'') | y), K) with M'' == (M' & M)
>
> For example, code like:
> int foo(int x, int y)
> {
> return (((x & 0xfffffff0) | y) & 0xfff);
> }
>
> is now simplified into:
> foo:
> and.32 %r2 <- %arg1, $0xff0
> or.32 %r4 <- %r2, %arg2
> and.32 %r5 <- %r4, $0xfff
> ret.32 %r5
>
> while previously, the mask was not reduced:
> foo:
> and.32 %r2 <- %arg1, $0xfffffff0
> ...
>
> Note: this is not a very effective simplification like directly
> removing an instruction, nevertheless the smaller mask can
> trigger other simplifications and may also be advantageous
> for a subsequent code generation phase.
Heh, just before reading this note, I was thinking: this is not
all that good a simplification, its just a smaller mask, what
gives ... :-D
ATB,
Ramsay Jones
>
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
> ---
> simplify.c | 5 +++++
> validation/optim/and-or-bf2.c | 1 -
> validation/optim/and-or-lsr2.c | 1 -
> validation/optim/and-or-mask2.c | 1 -
> 4 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/simplify.c b/simplify.c
> index 01e4b489a..e985a1db7 100644
> --- a/simplify.c
> +++ b/simplify.c
> @@ -578,6 +578,11 @@ static int simplify_mask_or_and(struct instruction *insn, unsigned long long mas
> // if (M' & M) == M: ((a & M') | b) -> (a | b)
> return replace_pseudo(or, arg, and->src1);
> }
> + if (nmask != omask && !multi_users(ora)) {
> + // if (M' & M) != M': AND(a, M') -> AND(a, (M' & M))
> + and->src2 = value_pseudo(nmask);
> + return REPEAT_CSE;
> + }
> return 0;
> }
>
> diff --git a/validation/optim/and-or-bf2.c b/validation/optim/and-or-bf2.c
> index cccaa85bc..2296da122 100644
> --- a/validation/optim/and-or-bf2.c
> +++ b/validation/optim/and-or-bf2.c
> @@ -14,7 +14,6 @@ void foo(struct s *p)
> /*
> * check-name: and-or-bf2
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-start
> foo:
> diff --git a/validation/optim/and-or-lsr2.c b/validation/optim/and-or-lsr2.c
> index a0df29631..d1af0135d 100644
> --- a/validation/optim/and-or-lsr2.c
> +++ b/validation/optim/and-or-lsr2.c
> @@ -6,7 +6,6 @@ int foo(int x, int y)
> /*
> * check-name: and-or-lsr2
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-ignore
> * check-output-contains: and\\..*\\$0xf0fff
> diff --git a/validation/optim/and-or-mask2.c b/validation/optim/and-or-mask2.c
> index 6c340c7ee..cab802a66 100644
> --- a/validation/optim/and-or-mask2.c
> +++ b/validation/optim/and-or-mask2.c
> @@ -6,7 +6,6 @@ int foo(int x, int y)
> /*
> * check-name: and-or-mask2
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-ignore
> * check-output-contains: and\\..*\\$0xf0f
>
