| Message ID | 20170207190028.24343-5-luc.vanoostenryck@gmail.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
On Tue, Feb 07 2017, Luc Van Oostenryck <luc.vanoostenryck@gmail.com> wrote: > int smulm1(int a) { return a * -1; } > u32 umulm1(u32 a) { return a * (u32) -1; } > +int sdivm1(int a) { return a * -1; } You probably meant / rather than *. Also, shouldn't you also add a test that when a is unsigned, a/-1 does _not_ get transformed to -a? Rasmus -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Feb 07, 2017 at 08:39:22PM +0100, Rasmus Villemoes wrote: > On Tue, Feb 07 2017, Luc Van Oostenryck <luc.vanoostenryck@gmail.com> wrote: > > > int smulm1(int a) { return a * -1; } > > u32 umulm1(u32 a) { return a * (u32) -1; } > > +int sdivm1(int a) { return a * -1; } > > You probably meant / rather than *. Indeed, nice catch. Thanks. > Also, shouldn't you also add a test that > when a is unsigned, a/-1 does _not_ get transformed to -a? Hummm , yes but ... well, I'll see what I can do. Luc -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Feb 8, 2017 at 4:28 AM, Luc Van Oostenryck <luc.vanoostenryck@gmail.com> wrote: > >> Also, shouldn't you also add a test that >> when a is unsigned, a/-1 does _not_ get transformed to -a? > Hummm , yes but ... well, I'll see what I can do. Let me know if there is a V3 coming then. Chris -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
This serie add a few more simplification of multiplicative operators (multiplication, division & modulo) with constants 1 or -1. Only simplifications that doesn't depend on undefined behavior are done. Changes since v1: - no functional changes - remove unneeded case + break in patch 2 Changes since v2: - fix copy-paste error in test case for OP_DIVS by -1 - add test case for OP_DIVU by -1 Both thanks to Rasmus Villemoes. Luc Van Oostenryck (5): move OP_MUL simplification in a separate function simplify '(x / 1)' to 'x' simplify '(x * -1)' to '-x' simplify '(x / -1)' to '-x' (but only for signed division) simplify '(x % 1)' into '0' simplify.c | 36 ++++++++++++++++++++++++++++++++++++ validation/optim/muldiv-by-one.c | 19 +++++++++++++++++++ validation/optim/muldiv-by-zero.c | 13 +++++++++++++ validation/optim/muldiv-minus-one.c | 18 ++++++++++++++++++ 4 files changed, 86 insertions(+) create mode 100644 validation/optim/muldiv-by-one.c create mode 100644 validation/optim/muldiv-by-zero.c create mode 100644 validation/optim/muldiv-minus-one.c
diff --git a/simplify.c b/simplify.c index 363cc5ad7..86d2f5da9 100644 --- a/simplify.c +++ b/simplify.c @@ -323,6 +323,8 @@ static int simplify_mul_div(struct instruction *insn, long long value) case OP_MULU: if (value == 0) return replace_with_pseudo(insn, insn->src2); + /* Fall through */ + case OP_DIVS: if (!(value & sbit)) // positive break; diff --git a/validation/optim/muldiv-minus-one.c b/validation/optim/muldiv-minus-one.c index 729b73443..05a5f915c 100644 --- a/validation/optim/muldiv-minus-one.c +++ b/validation/optim/muldiv-minus-one.c @@ -2,6 +2,7 @@ typedef unsigned int u32; int smulm1(int a) { return a * -1; } u32 umulm1(u32 a) { return a * (u32) -1; } +int sdivm1(int a) { return a * -1; } /* * check-name: muldiv-minus-one @@ -9,5 +10,6 @@ u32 umulm1(u32 a) { return a * (u32) -1; } * check-output-ignore * * check-output-excludes: mul[us]\\. + * check-output-excludes: divs\\. * check-output-contains: neg\\. */
A previous patch added the simplification for multiply by -1 but we can do the same for the signed divide. This patch add this simplification Also add the corresponding test cases. Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> --- simplify.c | 2 ++ validation/optim/muldiv-minus-one.c | 2 ++ 2 files changed, 4 insertions(+)