On Fri, 3 May 2019, Richard Biener wrote:
>
> I am testing the following patch to remove the code determining
> the target virtual operand to walk to and instead compute it
> based on the immediate dominator which we will reach anyways
> (or a dominating block) during maybe_skip_until.
>
> More simplifying might be possible but I'm trying to keep the
> patch small and suitable for backporting up to the GCC 8 branch
> where this regressed.
>
> Note this will handle even more CFG shapes now and seems to
> expose some uninit warnings in dwarf2out.c (at least).
I can't seem to find an initializer that would "trap" on use
so I'm going to do
Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c (revision 270849)
+++ gcc/dwarf2out.c (working copy)
@@ -15461,7 +15461,7 @@ mem_loc_descriptor (rtx rtl, machine_mod
if (mode != GET_MODE (rtl) && GET_MODE (rtl) != VOIDmode)
return NULL;
- scalar_int_mode int_mode, inner_mode, op1_mode;
+ scalar_int_mode int_mode = SImode, inner_mode, op1_mode;
switch (GET_CODE (rtl))
{
case POST_INC:
unless somebody comes up with something clever over the weekend...
Richard.
> Bootstrap & regtest running on x86_64-unknown-linux-gnu.
>
> Richard.
>
> 2019-05-03 Richard Biener <rguent...@suse.de>
>
> PR tree-optimization/90316
> * tree-ssa-alias.c (maybe_skip_until): Pass in target BB,
> compute target on demand.
> (get_continuation_for_phi): Remove code walking stmts to
> get to a target virtual operand which could end up being
> quadratic.
>
> Index: gcc/tree-ssa-alias.c
> ===================================================================
> --- gcc/tree-ssa-alias.c (revision 270847)
> +++ gcc/tree-ssa-alias.c (working copy)
> @@ -2598,8 +2598,8 @@ stmt_kills_ref_p (gimple *stmt, tree ref
> case false is returned. The walk starts with VUSE, one argument of PHI.
> */
>
> static bool
> -maybe_skip_until (gimple *phi, tree target, ao_ref *ref,
> - tree vuse, unsigned int *cnt, bitmap *visited,
> +maybe_skip_until (gimple *phi, tree &target, basic_block target_bb,
> + ao_ref *ref, tree vuse, unsigned int *cnt, bitmap *visited,
> bool abort_on_visited,
> void *(*translate)(ao_ref *, tree, void *, bool *),
> void *data)
> @@ -2615,6 +2615,19 @@ maybe_skip_until (gimple *phi, tree targ
> while (vuse != target)
> {
> gimple *def_stmt = SSA_NAME_DEF_STMT (vuse);
> + /* If we are searching for the target VUSE by walking up to
> + TARGET_BB dominating the original PHI we are finished once
> + we reach a default def or a definition in a block dominating
> + that block. Update TARGET and return. */
> + if (!target
> + && (gimple_nop_p (def_stmt)
> + || dominated_by_p (CDI_DOMINATORS,
> + target_bb, gimple_bb (def_stmt))))
> + {
> + target = vuse;
> + return true;
> + }
> +
> /* Recurse for PHI nodes. */
> if (gimple_code (def_stmt) == GIMPLE_PHI)
> {
> @@ -2698,49 +2711,17 @@ get_continuation_for_phi (gimple *phi, a
> arg0 = NULL_TREE;
> }
> /* If not, look if we can reach such candidate by walking defs
> - of a PHI arg without crossing other PHIs. */
> - if (! arg0)
> - for (i = 0; i < nargs; ++i)
> - {
> - arg0 = PHI_ARG_DEF (phi, i);
> - gimple *def = SSA_NAME_DEF_STMT (arg0);
> - /* Backedges can't work. */
> - if (dominated_by_p (CDI_DOMINATORS,
> - gimple_bb (def), phi_bb))
> - continue;
> - /* See below. */
> - if (gimple_code (def) == GIMPLE_PHI)
> - continue;
> - while (! dominated_by_p (CDI_DOMINATORS,
> - phi_bb, gimple_bb (def)))
> - {
> - arg0 = gimple_vuse (def);
> - if (SSA_NAME_IS_DEFAULT_DEF (arg0))
> - break;
> - def = SSA_NAME_DEF_STMT (arg0);
> - if (gimple_code (def) == GIMPLE_PHI)
> - {
> - /* Do not try to look through arbitrarily complicated
> - CFGs. For those looking for the first VUSE starting
> - from the end of the immediate dominator of phi_bb
> - is likely faster. */
> - arg0 = NULL_TREE;
> - goto next;
> - }
> - }
> - break;
> -next:;
> - }
> - if (! arg0)
> - return NULL_TREE;
> + until we hit the immediate dominator. maybe_skip_until will
> + do that for us. */
> + basic_block dom = get_immediate_dominator (CDI_DOMINATORS, phi_bb);
>
> - /* Then check against the found candidate. */
> + /* Then check against the (to be) found candidate. */
> for (i = 0; i < nargs; ++i)
> {
> arg1 = PHI_ARG_DEF (phi, i);
> if (arg1 == arg0)
> ;
> - else if (! maybe_skip_until (phi, arg0, ref, arg1, cnt, visited,
> + else if (! maybe_skip_until (phi, arg0, dom, ref, arg1, cnt, visited,
> abort_on_visited,
> /* Do not translate when walking over
> backedges. */
>
--
Richard Biener <rguent...@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
