https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87948
Bug ID: 87948
Summary: LRA register allocator does not support
HARD_REGNO_CALLER_SAVE_MODE returning VOIDmode
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: meissner at gcc dot gnu.org
Target Milestone: ---
The documentation for HARD_REGNO_CALLER_SAVE_MODE states:
@defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs})
A C expression specifying which mode is required for saving @var{nregs}
of a pseudo-register in call-clobbered hard register @var{regno}. If
@var{regno} is unsuitable for caller save, @code{VOIDmode} should be
returned. For most machines this macro need not be defined since GCC
will select the smallest suitable mode.
@end defmac
I was trying to prevent the GCC compiler from saving and restoring CR registers
across calls, so I defined HARD_REGNO_CALLER_SAVE_MODE as:
/* When setting up caller-save slots (MODE == VOIDmode) ensure we allocate
enough space to account for vectors in FP regs. However, TFmode/TDmode
should not use VSX instructions to do a caller save. Return VOIDmode
for the CR registers so that we don't try to save them across calls. */
#define HARD_REGNO_CALLER_SAVE_MODE(REGNO, NREGS, MODE) \
(CR_REGNO_P (REGNO) \
? VOIDmode \
: (NREGS) <= rs6000_hard_regno_nregs[MODE][REGNO] \
? (MODE) \
: TARGET_VSX \
&& ((MODE) == VOIDmode || ALTIVEC_OR_VSX_VECTOR_MODE (MODE)) \
&& FP_REGNO_P (REGNO) \
? V2DFmode \
: FLOAT128_IBM_P (MODE) && FP_REGNO_P (REGNO) \
? DFmode \
: (MODE) == TDmode && FP_REGNO_P (REGNO) \
? DImode \
: choose_hard_reg_mode ((REGNO), (NREGS), false))
However, when I try to build the compiler (without bootstrap initially), I get
the following error:
during RTL pass: reload
/home/meissner/fsf-src/test/libbacktrace/elf.c: In function 'elf_add':
/home/meissner/fsf-src/test/libbacktrace/elf.c:3211:1: internal compiler error:
in lra_create_new_reg_with_unique_value, at lra.c:189
3211 | }
| ^
0x107bba3f lra_create_new_reg_with_unique_value(machine_mode, rtx_def*,
reg_class, char const*)
/home/meissner/fsf-src/test/gcc/lra.c:189
0x107bbabf lra_create_new_reg(machine_mode, rtx_def*, reg_class, char const*)
/home/meissner/fsf-src/test/gcc/lra.c:229
0x107ce00b split_reg
/home/meissner/fsf-src/test/gcc/lra-constraints.c:5566
0x107d5aa3 inherit_in_ebb
/home/meissner/fsf-src/test/gcc/lra-constraints.c:6568
0x107d5aa3 lra_inheritance()
/home/meissner/fsf-src/test/gcc/lra-constraints.c:6639
0x107c0f37 lra(_IO_FILE*)
/home/meissner/fsf-src/test/gcc/lra.c:2486
0x1075abeb do_reload
/home/meissner/fsf-src/test/gcc/ira.c:5469
0x1075abeb execute
/home/meissner/fsf-src/test/gcc/ira.c:5653
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Makefile:820: recipe for target 'elf.lo' failed
make[3]: *** [elf.lo] Error 1
make[3]: Leaving directory
'/home/meissner/fsf-build-ppc64le/test/powerpc64le-unknown-linux-gnu/libbacktrace'
Makefile:700: recipe for target 'all' failed
make[2]: *** [all] Error 2
make[2]: Leaving directory
'/home/meissner/fsf-build-ppc64le/test/powerpc64le-unknown-linux-gnu/libbacktrace'
Makefile:13084: recipe for target 'all-target-libbacktrace' failed
make[1]: *** [all-target-libbacktrace] Error 2
make[1]: Leaving directory '/home/meissner/fsf-build-ppc64le/test'
Makefile:939: recipe for target 'all' failed
make: *** [all] Error 2
