procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

PR rtl-optimization/112380: Defend against CLOBBERs in combine.cc

Browse source 
This patch addresses PR rtl-optimization/112380, an ICE-on-valid regression
where a (clobber (const_int 0)) encounters a sanity checking gcc_assert
(at line 7554) in simplify-rtx.cc.  These CLOBBERs are used internally
by GCC's combine pass much like error_mark_node is used by various
language front-ends.

The solutions are either to handle/accept these CLOBBERs through-out
(or in more places in) the middle-end's RTL optimizers, including functions
in simplify-rtx.cc that are used by passes other than combine, and/or
attempt to prevent these CLOBBERs escaping from try_combine into the
RTX/RTL stream.  The benefit of the second approach is that it actually
allows for better optimization: when try_combine fails to simplify an
expression instead of substituting a CLOBBER to avoid the instruction
pattern being recognized, noticing the CLOBBER often allows combine
to attempt alternate simplifications/transformations looking for those
that can be recognized.

This first alternative is the minimal fix to address the CLOBBER
encountered in the bugzilla PR.

2023-12-11  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	PR rtl-optimization/112380
	* combine.cc (expand_field_assignment): Check if gen_lowpart
	returned a CLOBBER, and avoid calling gen_simplify_binary with
	it if so.

gcc/testsuite/ChangeLog
	PR rtl-optimization/112380
	* gcc.dg/pr112380.c: New test case.
This commit is contained in:
Roger Sayle 2023-12-11 17:30:20 +00:00
parent 02f562484c
commit 624e274ca3
2 changed files with 39 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

9
gcc/combine.cc
View file

@ -7466,6 +7466,11 @@ expand_field_assignment (const_rtx x)
if (!targetm.scalar_mode_supported_p (compute_mode))
break;
/* gen_lowpart_for_combine returns CLOBBER on failure. */
rtx lowpart = gen_lowpart (compute_mode, SET_SRC (x));
if (GET_CODE (lowpart) == CLOBBER)
break;
/* Now compute the equivalent expression. Make a copy of INNER
for the SET_DEST in case it is a MEM into which we will substitute;
we don't want shared RTL in that case. */
@ -7480,9 +7485,7 @@ expand_field_assignment (const_rtx x)
inner);
masked = simplify_gen_binary (ASHIFT, compute_mode,
simplify_gen_binary (
AND, compute_mode,
gen_lowpart (compute_mode, SET_SRC (x)),
mask),
AND, compute_mode, lowpart, mask),
pos);
x = gen_rtx_SET (copy_rtx (inner),

33
gcc/testsuite/gcc.dg/pr112380.c Normal file
View file

@ -0,0 +1,33 @@
/* { dg-do compile } */
/* { dg-options "-O2" } */
enum { TGSI_FILE_NULL };
struct ureg_src {
unsigned File : 4;
unsigned : 2;
unsigned : 2;
unsigned : 2;
unsigned : 1;
unsigned IndirectFile : 4;
unsigned IndirectSwizzle : 2;
int : 16;
int : 6;
int : 16;
int : 16;
unsigned : 10;
} __trans_tmp_1;
int ureg_src_indirect_addr_1, ntt_emit_texture_instr_sampler_handle_src;
void ureg_scalar(struct ureg_src);
void ntt_emit_texture_instr() {
struct ureg_src sampler;
if (ntt_emit_texture_instr_sampler_handle_src)
sampler = __trans_tmp_1;
struct ureg_src reg = sampler;
reg.File != TGSI_FILE_NULL;
reg.IndirectFile = reg.IndirectSwizzle = ureg_src_indirect_addr_1;
sampler = reg;
ureg_scalar(reg);
}