On 23/08/18 23:24, Luc Van Oostenryck wrote:
> The simplication of AND(SHIFT(a | b, S), M) can be done by combining
s/simplication/simplification/
> the mask M with the effective mask corresponding to SHIFT(_, S).
>
> This intruction pattern is generated when accessing bitfields,
s/intruction/instruction/
ATB,
Ramsay Jones
> for example, code like:
> struct u {
> unsigned int :2;
> unsigned int f:3;
> };
> int bfu(struct u s, int a)
> {
> s.f = a;
> return s.f;
> }
>
> is now simplified into the minimal:
> bfu:
> and.32 %r11 <- %arg2, $7
> ret.32 %r11
>
> The simplification is done by introducing a small helper,
> simplify_mask_shift(), doing the pattern matching and then calling
> simplify_mask_shift_or() with the mask M.
>
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
> ---
> simplify.c | 18 ++++++++++++++++++
> validation/optim/and-or-bfu.c | 1 -
> validation/optim/bitfield-store-loadu.c | 1 -
> 3 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/simplify.c b/simplify.c
> index e398d727e..78688c7c3 100644
> --- a/simplify.c
> +++ b/simplify.c
> @@ -686,6 +686,21 @@ static int simplify_mask_shift_or(struct instruction *sh, struct instruction *or
> return simplify_mask_or(sh, smask & mask, or);
> }
>
> +static int simplify_mask_shift(struct instruction *sh, unsigned long long mask)
> +{
> + struct instruction *inner;
> +
> + if (!constant(sh->src2) || sh->tainted)
> + return 0;
> + switch (DEF_OPCODE(inner, sh->src1)) {
> + case OP_OR:
> + if (!multi_users(sh->target))
> + return simplify_mask_shift_or(sh, inner, mask);
> + break;
> + }
> + return 0;
> +}
> +
> static long long check_shift_count(struct instruction *insn, unsigned long long uval)
> {
> unsigned int size = insn->size;
> @@ -986,6 +1001,9 @@ static int simplify_constant_mask(struct instruction *insn, unsigned long long m
> goto oldsize;
> case OP_OR:
> return simplify_mask_or(insn, mask, def);
> + case OP_LSR:
> + case OP_SHL:
> + return simplify_mask_shift(def, mask);
> case OP_ZEXT:
> osize = def->orig_type->bit_size;
> /* fall through */
> diff --git a/validation/optim/and-or-bfu.c b/validation/optim/and-or-bfu.c
> index c9dcfc33e..b6a080bd1 100644
> --- a/validation/optim/and-or-bfu.c
> +++ b/validation/optim/and-or-bfu.c
> @@ -12,7 +12,6 @@ int bfu(struct u s, int a)
> /*
> * check-name: and-or-bfu
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-ignore
> * check-output-pattern(1): and\\.
> diff --git a/validation/optim/bitfield-store-loadu.c b/validation/optim/bitfield-store-loadu.c
> index 4c289504c..7fa1593d9 100644
> --- a/validation/optim/bitfield-store-loadu.c
> +++ b/validation/optim/bitfield-store-loadu.c
> @@ -12,7 +12,6 @@ int foo(struct s s, int a)
> /*
> * check-name: bitfield-store-load unsigned
> * check-command: test-linearize -Wno-decl $file
> - * check-known-to-fail
> *
> * check-output-ignore
> * check-output-excludes: shl\\.
>
