https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127056
Bug ID: 127056
Summary: [17 Regression] AArch64 prefetch insn broken since
r17-3557-ge2f3007f4d5
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: ice-on-valid-code
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: tnfchris at gcc dot gnu.org
CC: ktkachov at gcc dot gnu.org
Target Milestone: ---
Target: aarch64*
Following example
char (*a)[8];
int b;
void c() {
if (b >= 0)
__builtin_prefetch(a[b]);
}
compiled at -O1 -march=armv8-a is broken since
commit g:e2f3007f4d58dbf09b18f360895c5ca48f8503bb
Author: Kyrylo Tkachov <[email protected]>
Date: Fri Aug 14 17:04:40 2026 -0700
combine: give a prefetch address the same treatment as a MEM address
because the MEM_REF is no longer being merged into the INSN by combine.
This causes a reload to happen to
>>> p debug (insn)
(insn 36 16 37 3 (set (reg:DI 115)
(and:DI (mult:DI (subreg:DI (reg:SI 101 [ b.0_1 ]) 0)
(const_int 8 [0x8]))
(const_int 34359738360 [0x7fffffff8]))) "x264-ice.c":5:5 -1
(nil))
and we get an ICE because that new insn is bogus
internal compiler error: in lra_set_insn_recog_data, at lra.cc:1045
6 | }
| ^
0x3f0a9f7 internal_error(char const*, ...)
src/gcc/gcc/diagnostic-global-context.cc:787
0x3f1a7a0 fancy_abort(char const*, int, char const*)
src/gcc/gcc/diagnostics/context.cc:1813
0x18ad760 lra_set_insn_recog_data(rtx_insn*)
src/gcc/gcc/lra.cc:1045
0x18b2088 lra_get_insn_recog_data(rtx_insn*)
src/gcc/gcc/lra-int.h:546
0x18affea setup_sp_offset
src/gcc/gcc/lra.cc:1905
0x18b026d lra_process_new_insns(rtx_insn*, rtx_insn*, rtx_insn*, char const*,
bool)
src/gcc/gcc/lra.cc:1953
0x18cb103 curr_insn_transform
src/gcc/gcc/lra-constraints.cc:5472
0x18cd3f7 lra_constraints(bool)
src/gcc/gcc/lra-constraints.cc:6182
0x18b19d8 lra(_IO_FILE*, int)
src/gcc/gcc/lra.cc:2511
0x1852efd do_reload
src/gcc/gcc/ira.cc:6095
0x18533dc execute
src/gcc/gcc/ira.cc:6283
This breaks x264_r in SPECCPU 2017.
