diff options
| author | H.J. Lu <hjl.tools@gmail.com> | 2016-05-19 08:49:45 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2016-06-06 13:21:08 -0700 |
| commit | dff8bcdab5968ac53e52ef06cabe8d921b429d22 (patch) | |
| tree | d6c72f2aca3e3b1cb18b56e51e33a476e711b8f3 | |
| parent | aba9d000bf8441d77f0557af360e3aea7525d03e (diff) | |
| download | glibc-dff8bcdab5968ac53e52ef06cabe8d921b429d22.tar.gz | |
Remove alignments on jump targets in memset
X86-64 memset-vec-unaligned-erms.S aligns many jump targets, which
increases code sizes, but not necessarily improve performance. As
memset benchtest data of align vs no align on various Intel and AMD
processors
https://sourceware.org/bugzilla/attachment.cgi?id=9277
shows that aligning jump targets isn't necessary.
[BZ #20115]
* sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S (__memset):
Remove alignments on jump targets.
| -rw-r--r-- | sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S | 37 |
1 files changed, 5 insertions, 32 deletions
diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S index 89f6886393..28e71fd576 100644 --- a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S +++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S @@ -18,12 +18,10 @@ /* memset is implemented as: 1. Use overlapping store to avoid branch. - 2. Force 32-bit displacement for branches to avoid long nop between - instructions. - 3. If size is less than VEC, use integer register stores. - 4. If size is from VEC_SIZE to 2 * VEC_SIZE, use 2 VEC stores. - 5. If size is from 2 * VEC_SIZE to 4 * VEC_SIZE, use 4 VEC stores. - 6. If size is more to 4 * VEC_SIZE, align to 4 * VEC_SIZE with + 2. If size is less than VEC, use integer register stores. + 3. If size is from VEC_SIZE to 2 * VEC_SIZE, use 2 VEC stores. + 4. If size is from 2 * VEC_SIZE to 4 * VEC_SIZE, use 4 VEC stores. + 5. If size is more to 4 * VEC_SIZE, align to 4 * VEC_SIZE with 4 VEC stores and store 4 * VEC at a time until done. */ #include <sysdep.h> @@ -143,14 +141,10 @@ ENTRY (MEMSET_SYMBOL (__memset, unaligned_erms)) VZEROUPPER ret - .p2align 4 L(stosb_more_2x_vec): cmpq $REP_STOSB_THRESHOLD, %rdx - /* Force 32-bit displacement to avoid long nop between - instructions. */ - ja.d32 L(stosb) + ja L(stosb) #endif - .p2align 4 L(more_2x_vec): cmpq $(VEC_SIZE * 4), %rdx ja L(loop_start) @@ -162,26 +156,12 @@ L(return): VZEROUPPER ret - .p2align 4 L(loop_start): leaq (VEC_SIZE * 4)(%rdi), %rcx -# if VEC_SIZE == 32 || VEC_SIZE == 64 - /* Force 32-bit displacement to avoid long nop between - instructions. */ - VMOVU.d32 %VEC(0), (%rdi) -# else VMOVU %VEC(0), (%rdi) -# endif andq $-(VEC_SIZE * 4), %rcx -# if VEC_SIZE == 32 - /* Force 32-bit displacement to avoid long nop between - instructions. */ - VMOVU.d32 %VEC(0), -VEC_SIZE(%rdi,%rdx) - VMOVU.d32 %VEC(0), VEC_SIZE(%rdi) -# else VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx) VMOVU %VEC(0), VEC_SIZE(%rdi) -# endif VMOVU %VEC(0), -(VEC_SIZE * 2)(%rdi,%rdx) VMOVU %VEC(0), (VEC_SIZE * 2)(%rdi) VMOVU %VEC(0), -(VEC_SIZE * 3)(%rdi,%rdx) @@ -190,14 +170,7 @@ L(loop_start): addq %rdi, %rdx andq $-(VEC_SIZE * 4), %rdx cmpq %rdx, %rcx -# if VEC_SIZE == 32 || VEC_SIZE == 64 - /* Force 32-bit displacement to avoid long nop between - instructions. */ - je.d32 L(return) -# else je L(return) -# endif - .p2align 4 L(loop): VMOVA %VEC(0), (%rcx) VMOVA %VEC(0), VEC_SIZE(%rcx) |