From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Cc: nd <nd@arm.com>
Subject: [PATCH][AArch64] Improve legitimize_address
Date: Tue, 06 Sep 2016 13:31:00 -0000 [thread overview]
Message-ID: <AM5PR0802MB2610FED9736F1EBB2A34EAF783F90@AM5PR0802MB2610.eurprd08.prod.outlook.com> (raw)
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
OK for trunk?
ChangeLog:
2016-09-06 Wilco Dijkstra <wdijkstr@arm.com>
gcc/
* config/aarch64/aarch64.c (aarch64_legitimize_address):
Avoid use of base_offset if offset already in range.
--
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 27bbdbad8cddc576f9ed4fd0670116bd6d318412..119ff0aecb0c9f88899fa141b2c7f9158281f9c3 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -5058,9 +5058,19 @@ 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)
{
next reply other threads:[~2016-09-06 13:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-06 13:31 Wilco Dijkstra [this message]
2016-09-07 12:59 ` Richard Earnshaw (lists)
2016-09-07 20:04 ` Christophe Lyon
2016-09-08 11:56 ` Wilco Dijkstra
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