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[PR114415][scheduler]: Fixing wrong code generation

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For the test case, the insn scheduler (working for live range
shrinkage) moves insns modifying stack memory before an insn reserving
the stack memory. Comments in the patch contains more details about
the problem and its solution.

gcc/ChangeLog:

	PR rtl-optimization/114415
	* sched-deps.cc (add_insn_mem_dependence): Add memory check for mem argument.
	(sched_analyze_1): Treat stack pointer modification as memory read.
	(sched_analyze_2, sched_analyze_insn): Add memory guard for processing pending_read_mems.
	* sched-int.h (deps_desc): Add comment to pending_read_mems.

gcc/testsuite/ChangeLog:

	PR rtl-optimization/114415
	* gcc.target/i386/pr114415.c: New test.
This commit is contained in:
Vladimir N. Makarov 2024-04-04 16:04:04 -04:00
parent 7520a4992c
commit a24476422b
3 changed files with 83 additions and 17 deletions
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49
gcc/sched-deps.cc
View file

@ -1735,7 +1735,7 @@ add_insn_mem_dependence (class deps_desc *deps, bool read_p,
insn_node = alloc_INSN_LIST (insn, *insn_list);
*insn_list = insn_node;
if (sched_deps_info->use_cselib)
if (sched_deps_info->use_cselib && MEM_P (mem))
{
mem = shallow_copy_rtx (mem);
XEXP (mem, 0) = cselib_subst_to_values_from_insn (XEXP (mem, 0),
@ -2458,6 +2458,25 @@ sched_analyze_1 (class deps_desc *deps, rtx x, rtx_insn *insn)
FIRST_STACK_REG);
}
#endif
if (!deps->readonly && regno == STACK_POINTER_REGNUM)
{
/* Please see PR114115. We have insn modifying memory on the stack
and not addressed by stack pointer and we have insn reserving the
stack space. If we move the insn modifying memory before insn
reserving the stack space, we can change memory out of the red
zone. Even worse, some optimizations (e.g. peephole) can add
insns using temporary stack slots before insn reserving the stack
space but after the insn modifying memory. This will corrupt the
modified memory. Therefore we treat insn changing the stack as
reading unknown memory. This will create anti-dependence. We
don't need to treat the insn as writing memory because GCC by
itself does not generate code reading undefined stack memory. */
if ((deps->pending_read_list_length + deps->pending_write_list_length)
>= param_max_pending_list_length
&& !DEBUG_INSN_P (insn))
flush_pending_lists (deps, insn, true, true);
add_insn_mem_dependence (deps, true, insn, dest);
}
}
else if (MEM_P (dest))
{
@ -2498,10 +2517,11 @@ sched_analyze_1 (class deps_desc *deps, rtx x, rtx_insn *insn)
pending_mem = deps->pending_read_mems;
while (pending)
{
if (anti_dependence (pending_mem->element (), t)
&& ! sched_insns_conditions_mutex_p (insn, pending->insn ()))
note_mem_dep (t, pending_mem->element (), pending->insn (),
DEP_ANTI);
rtx mem = pending_mem->element ();
if (REG_P (mem)
|| (anti_dependence (mem, t)
&& ! sched_insns_conditions_mutex_p (insn, pending->insn ())))
note_mem_dep (t, mem, pending->insn (), DEP_ANTI);
pending = pending->next ();
pending_mem = pending_mem->next ();
@ -2637,12 +2657,10 @@ sched_analyze_2 (class deps_desc *deps, rtx x, rtx_insn *insn)
pending_mem = deps->pending_read_mems;
while (pending)
{
if (read_dependence (pending_mem->element (), t)
&& ! sched_insns_conditions_mutex_p (insn,
pending->insn ()))
note_mem_dep (t, pending_mem->element (),
pending->insn (),
DEP_ANTI);
rtx mem = pending_mem->element ();
if (MEM_P (mem) && read_dependence (mem, t)
&& ! sched_insns_conditions_mutex_p (insn, pending->insn ()))
note_mem_dep (t, mem, pending->insn (), DEP_ANTI);
pending = pending->next ();
pending_mem = pending_mem->next ();
@ -3026,8 +3044,7 @@ sched_analyze_insn (class deps_desc *deps, rtx x, rtx_insn *insn)
while (pending)
{
if (! sched_insns_conditions_mutex_p (insn, pending->insn ()))
add_dependence (insn, pending->insn (),
REG_DEP_OUTPUT);
add_dependence (insn, pending->insn (), REG_DEP_OUTPUT);
pending = pending->next ();
pending_mem = pending_mem->next ();
}
@ -3036,10 +3053,10 @@ sched_analyze_insn (class deps_desc *deps, rtx x, rtx_insn *insn)
pending_mem = deps->pending_read_mems;
while (pending)
{
if (MEM_VOLATILE_P (pending_mem->element ())
rtx mem = pending_mem->element ();
if (MEM_P (mem) && MEM_VOLATILE_P (mem)
&& ! sched_insns_conditions_mutex_p (insn, pending->insn ()))
add_dependence (insn, pending->insn (),
REG_DEP_OUTPUT);
add_dependence (insn, pending->insn (), REG_DEP_OUTPUT);
pending = pending->next ();
pending_mem = pending_mem->next ();
}

4
gcc/sched-int.h
View file

@ -471,7 +471,9 @@ public:
/* An INSN_LIST containing all insns with pending read operations. */
rtx_insn_list *pending_read_insns;
/* An EXPR_LIST containing all MEM rtx's which are pending reads. */
/* An EXPR_LIST containing all MEM rtx's which are pending reads. The list
can contain stack pointer instead of memory. This is a special case (see
sched-deps.cc::sched_analyze_1). */
rtx_expr_list *pending_read_mems;
/* An INSN_LIST containing all insns with pending write operations. */

47
gcc/testsuite/gcc.target/i386/pr114415.c Normal file
View file

@ -0,0 +1,47 @@
/* { dg-do run { target int128 } } */
/* { dg-options "-Oz -fno-dce -fno-forward-propagate -flive-range-shrinkage -fweb -Wno-psabi" } */
typedef unsigned V __attribute__((vector_size (64)));
typedef unsigned __int128 W __attribute__((vector_size (64)));
__int128 i;
V v;
W w;
W
bar2 (V, W c)
{
v |= (V){c[3]};
i = 0;
return c;
}
W
bar1 (W, W d)
{
v[0] %= 2;
return d;
}
W
bar0 (V a, W b)
{
W t = bar2 ((V) { }, w);
(void)bar2 ((V){b[0] - a[0]}, (W){});
b += bar1 (t, (W){1});
a[5] &= __builtin_mul_overflow_p (a[0], i, 0u);
return (W) a + b;
}
int
main ()
{
W x = bar0 ((V) { }, (W) { });
if (x[0] != 1)
__builtin_abort();
if (x[1])
__builtin_abort();
if (x[2])
__builtin_abort();
if (x[3])
__builtin_abort();
}