From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
For some reason GCC 6.2.1 here unrolls the from and to stack memcpy
here in per-byte fashion and also by repeatedly loading offset
constants. It look horrible like this for example:
...
fdc: 48 b8 41 00 00 00 00 movabs rax,0xffff880000000041
fe3: 88 ff ff
fe6: 44 88 74 06 80 mov BYTE PTR [rsi+rax*1-0x80],r14b
feb: 48 b8 42 00 00 00 00 movabs rax,0xffff880000000042
ff2: 88 ff ff
ff5: 44 88 6c 06 80 mov BYTE PTR [rsi+rax*1-0x80],r13b
ffa: 48 b8 43 00 00 00 00 movabs rax,0xffff880000000043
1001: 88 ff ff
1004: 44 88 64 06 80 mov BYTE PTR [rsi+rax*1-0x80],r12b
1009: 48 b8 44 00 00 00 00 movabs rax,0xffff880000000044
1010: 88 ff ff
1013: 88 5c 06 80 mov BYTE PTR [rsi+rax*1-0x80],bl
1017: 48 b8 45 00 00 00 00 movabs rax,0xffff880000000045
101e: 88 ff ff
1021: 44 88 5c 06 80 mov BYTE PTR [rsi+rax*1-0x80],r11b
1026: 48 b8 46 00 00 00 00 movabs rax,0xffff880000000046
102d: 88 ff ff
1030: 44 88 54 06 80 mov BYTE PTR [rsi+rax*1-0x80],r10b
1035: 48 b8 47 00 00 00 00 movabs rax,0xffff880000000047
103c: 88 ff ff
103f: 44 88 4c 06 80 mov BYTE PTR [rsi+rax*1-0x80],r9b
1044: 0f b6 5d d0 movzx ebx,BYTE PTR [rbp-0x30]
1048: 48 b8 48 00 00 00 00 movabs rax,0xffff880000000048
104f: 88 ff ff
1052: 88 5c 06 80 mov BYTE PTR [rsi+rax*1-0x80],bl
1056: 48 b8 49 00 00 00 00 movabs rax,0xffff880000000049
105d: 88 ff ff
1060: 40 88 7c 06 80 mov BYTE PTR [rsi+rax*1-0x80],dil
1065: 0f b6 5d cf movzx ebx,BYTE PTR [rbp-0x31]
1069: 48 b8 4a 00 00 00 00 movabs rax,0xffff88000000004a
1070: 88 ff ff
1073: 88 5c 06 80 mov BYTE PTR [rsi+rax*1-0x80],bl
1077: 0f b6 7d ce movzx edi,BYTE PTR [rbp-0x32]
107b: 48 b8 4b 00 00 00 00 movabs rax,0xffff88000000004b
...
So change the code a bit which makes it generate a more reasonable
code like:
...
bf1: 48 89 78 b8 mov QWORD PTR [rax-0x48],rdi
bf5: 4c 89 60 c0 mov QWORD PTR [rax-0x40],r12
bf9: 48 89 58 c8 mov QWORD PTR [rax-0x38],rbx
bfd: 4c 89 58 d0 mov QWORD PTR [rax-0x30],r11
c01: 4c 89 50 d8 mov QWORD PTR [rax-0x28],r10
...
Which saves 2087 bytes of code.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_fence_reg.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
index e03983973252..d665d2e74641 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence_reg.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
@@ -631,9 +631,9 @@ i915_gem_swizzle_page(struct page *page)
vaddr = kmap(page);
for (i = 0; i < PAGE_SIZE; i += 128) {
- memcpy(temp, &vaddr[i], 64);
+ memcpy(&temp[0], &vaddr[i], 64);
memcpy(&vaddr[i], &vaddr[i + 64], 64);
- memcpy(&vaddr[i + 64], temp, 64);
+ memcpy(&vaddr[i + 64], &temp[0], 64);
}
kunmap(page);
--
2.7.4
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