Changes since version 2:
patch 1 is reworked again.
patch 2 is unchanged from v2, it's included here only for completeness.
patch 3 is unchanged, it's included here only for completeness.
-------------
This short patch series is designed to address some more cases where we
can usefully lower memcpy operations during gimple fold. The current
code restricts this lowering to a maximum size of MOVE_MAX, ie the size
of a single integer register on the machine, but with modern architectures
this is likely too restrictive. The motivating example is
uint64_t bar64(const uint8_t *rData1)
{
uint64_t buffer;
__builtin_memcpy(&buffer, rData1, sizeof(buffer));
return buffer;
}
which on a 32-bit machine ends up with an inlined memcpy followed by a
load from the copied buffer.
The patch series is in three parts, although the middle patch is an
arm-specific tweak to handle unaligned 64-bit moves on more versions
of the Arm architecture.
Patch 1 changes gen_highpart to directly handle forming the highpart
of a MEM by calling adjust_address, this removes the need to validate
a MEM on return from simplify_gen_subreg, so we replace that with an
assert.
Patch 2 addresses an issue in the arm backend. Currently
movmisaligndi only supports vector targets. This patch reworks the
code so that the pattern can work on any architecture version that
supports misaligned accesses.
Patch 3 then relaxes the gimple fold simplification of memcpy to allow
larger memcpy operations to be folded away, provided that the total
size is less than MOVE_MAX * MOVE_RATIO and provided that the machine
has a suitable SET insn for the appropriate integer mode.
With these three changes, the testcase above now optimizes to
mov r3, r0
ldr r0, [r0] @ unaligned
ldr r1, [r3, #4] @ unaligned
bx lr
R.
Richard Earnshaw (3):
rtl: directly handle MEM in gen_highpart [PR102125]
arm: expand handling of movmisalign for DImode [PR102125]
gimple: allow more folding of memcpy [PR102125]
gcc/config/arm/arm.md | 16 ++++++++++++++++
gcc/config/arm/vec-common.md | 4 ++--
gcc/emit-rtl.c | 23 +++++++++++++----------
gcc/gimple-fold.c | 16 +++++++++++-----
4 files changed, 42 insertions(+), 17 deletions(-)
--
2.25.1
