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i386: Improve memory copy from named address space [PR111657]

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The stringop strategy selection algorithm falls back to a libcall strategy
when it exhausts its pool of available strategies.  The memory area copy
function (memcpy) is not availabe from the system library for non-default
address spaces, so the compiler emits the most trivial byte-at-a-time
copy loop instead.

The compiler should instead emit an optimized copy loop as a fallback for
non-default address spaces.

	PR target/111657

gcc/ChangeLog:

	* config/i386/i386-expand.cc (alg_usable_p): Reject libcall
	strategy for non-default address spaces.
	(decide_alg): Use loop strategy as a fallback strategy for
	non-default address spaces.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr111657.c: New test.
This commit is contained in:
Uros Bizjak 2023-10-05 17:40:37 +02:00
parent e866d08d8b
commit c6bff80d78
2 changed files with 19 additions and 1 deletions
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11
gcc/config/i386/i386-expand.cc
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@ -8320,6 +8320,11 @@ alg_usable_p (enum stringop_alg alg, bool memset, bool have_as)
{
if (alg == no_stringop)
return false;
/* It is not possible to use a library call if we have non-default
address space. We can do better than the generic byte-at-a-time
loop, used as a fallback. */
if (alg == libcall && have_as)
return false;
if (alg == vector_loop)
return TARGET_SSE || TARGET_AVX;
/* Algorithms using the rep prefix want at least edi and ecx;
@ -8494,8 +8499,12 @@ decide_alg (HOST_WIDE_INT count, HOST_WIDE_INT expected_size,
gcc_assert (alg != libcall);
return alg;
}
/* Try to use some reasonable fallback algorithm. Note that for
non-default address spaces we default to a loop instead of
a libcall. */
return (alg_usable_p (algs->unknown_size, memset, have_as)
? algs->unknown_size : libcall);
? algs->unknown_size : have_as ? loop : libcall);
}
/* Decide on alignment. We know that the operand is already aligned to ALIGN

9
gcc/testsuite/gcc.target/i386/pr111657.c Normal file
View file

@ -0,0 +1,9 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-rtl-expand -mno-sse" } */
struct a { long arr[30]; };
__seg_gs struct a m;
void bar (struct a *dst) { *dst = m; }
/* { dg-final { scan-rtl-dump-not "libcall" "expand" } } */