On November 16, 2018 10:23:33 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>The documentation for this function says that it wants to go through
>all
>(integral) conversions (both promotions and demotions), as long as the
>whole sequence of conversions is functionally equivalent to
>(optionally)
>casting the returned value to a signed or unsigned type with the same
>precision as the returned value (depending on the ->type filled in)
>and then (optionally) promoting it to the original argument's type.
>
>On the following testcase, we have:
> _39 = (long int) iftmp.0_19;
>in the loop and
> _4 = _2 >> a.4_3;
> iftmp.0_19 = (signed char) _4;
>before the loop, with
> int _4;
> signed char iftmp.0_19;
> long int _39;
>Currently we return _4, which is incorrect, we can't represent the
>series of
>conversions as simple zero or sign extension from int to long int,
>because
>there is a (signed char) cast in the middle. So, instead of returning
>_4 we
>need to return iftmp.0_19 in this case. That doesn't mean we need to
>stop
>the search for further candidates at that point, but just that all
>further
>candidates need to be at most with that precision.
>
>The following patch fixes that, bootstrapped/regtested on x86_64-linux
>and
>i686-linux, ok for trunk?
OK.
Richard.
>2018-11-16 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/87546
> * tree-vect-patterns.c (vect_look_through_possible_promotion): Add
> min_precision variable, initially set it to orig_precision, only does
> something if op_type's precision is <= min_precision and update
> min_precision whenever calling set_op.
>
> * gcc.dg/vect/O3-pr87546.c: New test.
>
>--- gcc/tree-vect-patterns.c.jj 2018-10-23 10:13:25.200876565 +0200
>+++ gcc/tree-vect-patterns.c 2018-11-16 16:53:08.668610905 +0100
>@@ -367,6 +367,7 @@ vect_look_through_possible_promotion (ve
> tree res = NULL_TREE;
> tree op_type = TREE_TYPE (op);
> unsigned int orig_precision = TYPE_PRECISION (op_type);
>+ unsigned int min_precision = orig_precision;
> stmt_vec_info caster = NULL;
> while (TREE_CODE (op) == SSA_NAME && INTEGRAL_TYPE_P (op_type))
> {
>@@ -385,7 +386,7 @@ vect_look_through_possible_promotion (ve
> This copes with cases such as the result of an arithmetic
> operation being truncated before being stored, and where that
> arithmetic operation has been recognized as an over-widened one. */
>- if (TYPE_PRECISION (op_type) <= orig_precision)
>+ if (TYPE_PRECISION (op_type) <= min_precision)
> {
> /* Use OP as the UNPROM described above if we haven't yet
> found a promotion, or if using the new input preserves the
>@@ -393,7 +394,10 @@ vect_look_through_possible_promotion (ve
> if (!res
> || TYPE_PRECISION (unprom->type) == orig_precision
> || TYPE_SIGN (unprom->type) == TYPE_SIGN (op_type))
>- unprom->set_op (op, dt, caster);
>+ {
>+ unprom->set_op (op, dt, caster);
>+ min_precision = TYPE_PRECISION (op_type);
>+ }
> /* Stop if we've already seen a promotion and if this
> conversion does more than change the sign. */
> else if (TYPE_PRECISION (op_type)
>--- gcc/testsuite/gcc.dg/vect/O3-pr87546.c.jj 2018-11-16
>17:03:39.294149070 +0100
>+++ gcc/testsuite/gcc.dg/vect/O3-pr87546.c 2018-11-16
>17:05:25.620385151 +0100
>@@ -0,0 +1,29 @@
>+#include "tree-vect.h"
>+
>+int a;
>+long b, f;
>+signed char c, g;
>+short int d = 219;
>+int e[64];
>+
>+__attribute__((noipa)) void
>+foo (void)
>+{
>+ asm volatile ("" : : "g" (&a), "g" (&d) : "memory");
>+ for (c = 0; c < 64; c++)
>+ {
>+ g = d < 0 ? d : d >> a;
>+ f = g + b;
>+ e[c] = f;
>+ }
>+ if (e[1] != (signed char) d)
>+ __builtin_abort ();
>+}
>+
>+int
>+main ()
>+{
>+ check_vect ();
>+ foo ();
>+ return 0;
>+}
>
>
> Jakub
