From 371905d12259c180efb9b1f1b5716e969feb60f9 Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Wed, 6 May 2020 09:39:45 +0200 Subject: [PATCH] tree-optimization/94963 - avoid bogus uninit warning with store-motion Eliding the load for store-motion causes an uninitialized variable flowing into the loop, conditionally initialized and used. The uninit warning cannot relate the flag used to guard the initialization and use with the actual initialization so the following robustifies the previous approach of marking the conditional store as not to be warned on by instead initializing the variable on loop entry from an uninitialized variable we mark as not to be warned for. 2020-05-06 Richard Biener PR tree-optimization/94963 * tree-ssa-loop-im.c (execute_sm_if_changed): Remove no-warning marking of the conditional store. (execute_sm): Instead mark the uninitialized state on loop entry to be not warned about. * gcc.dg/pr94963.c: New testcase. --- gcc/ChangeLog | 8 ++++++++ gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/gcc.dg/pr94963.c | 35 ++++++++++++++++++++++++++++++++++ gcc/tree-ssa-loop-im.c | 18 ++++++++++------- 4 files changed, 59 insertions(+), 7 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/pr94963.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index c40d8879274..73a601528f0 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2020-05-06 Richard Biener + + PR tree-optimization/94963 + * tree-ssa-loop-im.c (execute_sm_if_changed): Remove + no-warning marking of the conditional store. + (execute_sm): Instead mark the uninitialized state + on loop entry to be not warned about. + 2020-05-06 Hongtao Liu * common/config/i386/i386-common.c (OPTION_MASK_ISA2_TSXLDTRK_SET, diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index b917e810588..a3cf68d0a10 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2020-05-06 Richard Biener + + PR tree-optimization/94963 + * gcc.dg/pr94963.c: New testcase. + 2020-05-06 Hongtao Liu * g++.dg/other/i386-2.c: Add -mtsxldtrk. diff --git a/gcc/testsuite/gcc.dg/pr94963.c b/gcc/testsuite/gcc.dg/pr94963.c new file mode 100644 index 00000000000..aca9e161301 --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr94963.c @@ -0,0 +1,35 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -Wall" } */ + +typedef struct +{ + int p1; + int p2; + int p3; +} P; +struct S +{ + int field; +}; +extern int v2; +extern void foo (struct S *map); +static struct S var; +const P *pv; +int ps; +void +f (void) +{ + if (pv != 0) + for (const P *ph = pv; ph < &pv[ps]; ++ph) + switch (ph->p1) + { + case 1: + v2 = ph->p2; + break; + case 2: + var.field = ph->p3; + break; + } + if (var.field != 0) /* { dg-bogus "uninitialized" } */ + foo (&var); +} diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c index 554dd4be5bb..3056b4bfed2 100644 --- a/gcc/tree-ssa-loop-im.c +++ b/gcc/tree-ssa-loop-im.c @@ -1994,8 +1994,6 @@ execute_sm_if_changed (edge ex, tree mem, tree tmp_var, tree flag, gsi = gsi_start_bb (then_bb); /* Insert actual store. */ stmt = gimple_build_assign (unshare_expr (mem), tmp_var); - /* Make sure to not warn about maybe-uninit uses of tmp_var here. */ - gimple_set_no_warning (stmt, true); gsi_insert_after (&gsi, stmt, GSI_CONTINUE_LINKING); edge e1 = single_succ_edge (new_bb); @@ -2149,13 +2147,19 @@ execute_sm (class loop *loop, vec exits, im_mem_ref *ref) store then. */ if ((!always_stored && !multi_threaded_model_p) || (ref->loaded && bitmap_bit_p (ref->loaded, loop->num))) + load = gimple_build_assign (tmp_var, unshare_expr (ref->mem.ref)); + else { - load = gimple_build_assign (tmp_var, unshare_expr (ref->mem.ref)); - lim_data = init_lim_data (load); - lim_data->max_loop = loop; - lim_data->tgt_loop = loop; - gsi_insert_before (&gsi, load, GSI_SAME_STMT); + /* If not emitting a load mark the uninitialized state on the + loop entry as not to be warned for. */ + tree uninit = create_tmp_reg (TREE_TYPE (tmp_var)); + TREE_NO_WARNING (uninit) = 1; + load = gimple_build_assign (tmp_var, uninit); } + lim_data = init_lim_data (load); + lim_data->max_loop = loop; + lim_data->tgt_loop = loop; + gsi_insert_before (&gsi, load, GSI_SAME_STMT); if (multi_threaded_model_p) { -- 2.30.2