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Improve aarch64_legitimize_address - avoid splitting the offset if it is supported.

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Improve aarch64_legitimize_address - avoid splitting the offset if it is
supported.  When we do split, take the mode size into account.  BLKmode
falls into the unaligned case but should be treated like LDP/STP.
This improves codesize slightly due to fewer base address calculations:

int f(int *p) { return p[5000] + p[7000]; }

Now generates:

f:
	add	x0, x0, 16384
	ldr	w1, [x0, 3616]
	ldr	w0, [x0, 11616]
	add	w0, w1, w0
	ret

instead of:

f:
	add	x1, x0, 16384
	add	x0, x0, 24576
	ldr	w1, [x1, 3616]
	ldr	w0, [x0, 3424]
	add	w0, w1, w0
	ret

    gcc/
	* config/aarch64/aarch64.c (aarch64_legitimize_address):
	Avoid use of base_offset if offset already in range.

From-SVN: r240026
This commit is contained in:
Wilco Dijkstra 2016-09-07 14:56:59 +00:00 committed by Wilco Dijkstra
parent ca235a8500
commit ff0f3f1cb5
2 changed files with 17 additions and 2 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2016-09-07 Wilco Dijkstra <wdijkstr@arm.com>
* config/aarch64/aarch64.c (aarch64_legitimize_address):
Avoid use of base_offset if offset already in range.
2016-09-07 Kaz Kojima <kkojima@gcc.gnu.org>
* config/sh/sh-protos.h (struct sh_atomic_model,

14
gcc/config/aarch64/aarch64.c
View File

@ -5082,9 +5082,19 @@ aarch64_legitimize_address (rtx x, rtx /* orig_x */, machine_mode mode)
/* For offsets aren't a multiple of the access size, the limit is
-256...255. */
else if (offset & (GET_MODE_SIZE (mode) - 1))
base_offset = (offset + 0x100) & ~0x1ff;
{
base_offset = (offset + 0x100) & ~0x1ff;
/* BLKmode typically uses LDP of X-registers. */
if (mode == BLKmode)
base_offset = (offset + 512) & ~0x3ff;
}
/* Small negative offsets are supported. */
else if (IN_RANGE (offset, -256, 0))
base_offset = 0;
/* Use 12-bit offset by access size. */
else
base_offset = offset & ~0xfff;
base_offset = offset & (~0xfff * GET_MODE_SIZE (mode));
if (base_offset != 0)
{