On Fri, Oct 24, 2025 at 10:23 PM Georg-Johann Lay <[email protected]> wrote:
>
> Am 24.10.25 um 15:45 schrieb H.J. Lu:
> > For x86, volatile memory can be used as source operand for loads. Add
> > -fcombine-op-with-volatile-memory-load to allow operations with volatile
> > memory load:
> >
> > 1. Add a field, try_combine_insn, to recog_data_d for the combine pass to
> > pass the instruction information to general_operand.
> > 2. Update recog_for_combine_1 to set recog_data.try_combine_insn and clear
> > when calling recog.
> > 3. Add a function, volatile_memory_ok, which returns true if volatile
> > memory is used for load and -fcombine-op-with-volatile-memory-load is
> > enabled.
> > 4. Update general_operand to call volatile_memory_ok to determine if
> > a memory operand is OK.
> >
> > Enabled at -O1 and higher for x86. It optimizes
>
> Hi, what's the reason why this is not enabled for all targets?
There are 2 reasons:
1. RISC processors only allow moves with memory. Since this optimization
only applies to other load operations, it is nop for most RISC processors.
2. Some GCC tests scan compiler assembly outputs which don't expect other
load operations with volatile memory. I have to disable this optimization
in 100+ x86 tests in my patch. If this is enabled for other targets, it may
cause many GCC tests failures.
If your target supports this, you can give it a try.
> Can it break volatile correctness or so?
No. My patch has some tests to verify the volatile correctness.
> Johann
>
>
> > extern volatile int bar;
> >
> > int
> > foo (int z)
> > {
> > z *= 123;
> > return bar + z;
> > }
> >
> > into
> >
> > foo:
> > imull $123, %edi, %eax
> > addl bar(%rip), %eax
> > ret
> >
> > instead of
> >
> > foo:
> > imull $123, %edi, %eax
> > movl bar(%rip), %edx
> > addl %edx, %eax
> > ret
> >
> > Tested with Linux kernel 6.17.4 on Intel Core i7-1195G7.
> >
> > gcc/
> >
> > PR target/122343
> > * combine.cc (recog_for_combine_1): Set and clear
> > recog_data.try_combine_insn when calling recog.
> > * common.opt (-fcombine-op-with-volatile-memory-load): New option.
> > * recog.cc (volatile_memory_ok): New.
> > (general_operand): Call volatile_memory_ok.
> > * recog.h (recog_data_d): Add try_combine_insn.
> > * config/i386/i386-options.cc (ix86_recompute_optlev_based_flags):
> > Set -fcombine-op-with-volatile-memory-load for -O1 and above if
> > unset.
> > * doc/invoke.texi: Document -fcombine-op-with-volatile-memory-load.
> >
> > gcc/testsuite/
> >
> > PR target/122343
> > * gcc.target/i386/avx10_2-bf16-1.c: Compile with
> > -fno-combine-op-with-volatile-memory-load.
> > * gcc.target/i386/avx10_2-convert-1.c: Likewise.
> > * gcc.target/i386/avx10_2-satcvt-1.c: Likewise.
> > * gcc.target/i386/avx512bf16-vcvtneps2bf16-1.c: Likewise.
> > * gcc.target/i386/avx512bf16vl-vcvtneps2bf16-1a.c: Likewise.
> > * gcc.target/i386/avx512bf16vl-vcvtneps2bf16-1b.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvtps2qq-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvtps2uqq-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvtqq2pd-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvtqq2ps-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvttps2qq-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvttps2uqq-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvtuqq2pd-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vcvtuqq2ps-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vfpclasspd-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vfpclassps-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vfpclasssd-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vfpclassss-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vpmullq-1.c: Likewise.
> > * gcc.target/i386/avx512dq-vpmullq-3.c: Likewise.
> > * gcc.target/i386/avx512fp16-complex-fma.c: Likewise.
> > * gcc.target/i386/avx512fp16-vaddph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtpd2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2dq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2pd-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2psx-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2qq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2udq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2uqq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2uw-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtph2w-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtps2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtqq2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvttph2dq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvttph2qq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvttph2udq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvttph2uqq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvttph2uw-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvttph2w-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vcvtuqq2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vfcmaddcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vfcmulcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vfmaddcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vfmulcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vfpclassph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vfpclasssh-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vaddph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtpd2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtph2dq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtph2psx-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtph2qq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtph2udq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtph2uqq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtph2uw-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtph2w-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtps2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtqq2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvttph2dq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvttph2udq-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvttph2uw-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvttph2w-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vcvtuqq2ph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vfcmaddcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vfcmulcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vfmaddcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vfmulcph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vfpclassph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vmulph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vrcpph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vrsqrtph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16vl-vsqrtph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vmulph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vrcpph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vrsqrtph-1a.c: Likewise.
> > * gcc.target/i386/avx512fp16-vsqrtph-1a.c: Likewise.
> > * gcc.target/i386/avx512f-pr100267-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtps2pd-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtsd2si-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtsd2si64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtsd2usi-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtsd2usi64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtss2si-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtss2si64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtss2usi-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvtss2usi64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttsd2si-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttsd2si64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttsd2usi-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttsd2usi64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttss2si-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttss2si64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttss2usi-1.c: Likewise.
> > * gcc.target/i386/avx512f-vcvttss2usi64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vmovapd-1.c: Likewise.
> > * gcc.target/i386/avx512f-vmovaps-1.c: Likewise.
> > * gcc.target/i386/avx512f-vmovdqa64-1.c: Likewise.
> > * gcc.target/i386/avx512f-vpandnq-1.c: Likewise.
> > * gcc.target/i386/avx512f-vpbroadcastd-1.c: Likewise.
> > * gcc.target/i386/avx512f-vpbroadcastq-1.c: Likewise.
> > * gcc.target/i386/avx512f-vpcmpeqq-1.c: Likewise.
> > * gcc.target/i386/avx512f-vpcmpequq-1.c: Likewise.
> > * gcc.target/i386/avx512f-vrndscalepd-1.c: Likewise.
> > * gcc.target/i386/avx512f-vrndscaleps-1.c: Likewise.
> > * gcc.target/i386/avx512vl-pr100267-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vcvtpd2ps-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vcvtpd2udq-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vcvttpd2udq-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vcvttps2udq-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vmovapd-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vmovaps-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vmovdqa64-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vpcmpeqq-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vpcmpequq-1.c: Likewise.
> > * gcc.target/i386/avx512vl-vpcmpuq-1.c: Likewise.
> > * gcc.target/i386/avx-ne-convert-1.c: Likewise.
> > * gcc.target/i386/pr122343-1a.c: New test.
> > * gcc.target/i386/pr122343-1b.c: Likewise.
> > * gcc.target/i386/pr122343-2a.c: Likewise.
> > * gcc.target/i386/pr122343-2b.c: Likewise.
> > * gcc.target/i386/pr122343-3.c: Likewise.
> > * gcc.target/i386/pr122343-4a.c: Likewise.
> > * gcc.target/i386/pr122343-4b.c: Likewise.
> >
> >
>
--
H.J.
