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Subject[PATCH] crc32-pclmul: remove useless relative addressing
In 32-bit mode, the x86 architecture can hold full 32-bit pointers.
Therefore, the code that copies the current address to the %ecx register
and uses %ecx-relative addressing is useless, we could just use absolute
addressing.

The processors have a stack of return addresses for branch prediction. If
we use a call instruction and pop the return address, it desynchronizes
the return stack and causes branch prediction misses.

This patch also moves the data to the .rodata section.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
arch/x86/crypto/crc32-pclmul_asm.S | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

Index: linux-2.6/arch/x86/crypto/crc32-pclmul_asm.S
===================================================================
--- linux-2.6.orig/arch/x86/crypto/crc32-pclmul_asm.S
+++ linux-2.6/arch/x86/crypto/crc32-pclmul_asm.S
@@ -41,6 +41,7 @@
#include <asm/inst.h>


+.section .rodata
.align 16
/*
* [x4*128+32 mod P(x) << 32)]' << 1 = 0x154442bd4
@@ -111,19 +112,13 @@ ENTRY(crc32_pclmul_le_16) /* buffer and
pxor CONSTANT, %xmm1
sub $0x40, LEN
add $0x40, BUF
-#ifndef __x86_64__
- /* This is for position independent code(-fPIC) support for 32bit */
- call delta
-delta:
- pop %ecx
-#endif
cmp $0x40, LEN
jb less_64

#ifdef __x86_64__
movdqa .Lconstant_R2R1(%rip), CONSTANT
#else
- movdqa .Lconstant_R2R1 - delta(%ecx), CONSTANT
+ movdqa .Lconstant_R2R1, CONSTANT
#endif

loop_64:/* 64 bytes Full cache line folding */
@@ -172,7 +167,7 @@ less_64:/* Folding cache line into 128b
#ifdef __x86_64__
movdqa .Lconstant_R4R3(%rip), CONSTANT
#else
- movdqa .Lconstant_R4R3 - delta(%ecx), CONSTANT
+ movdqa .Lconstant_R4R3, CONSTANT
#endif
prefetchnta (BUF)

@@ -220,8 +215,8 @@ fold_64:
movdqa .Lconstant_R5(%rip), CONSTANT
movdqa .Lconstant_mask32(%rip), %xmm3
#else
- movdqa .Lconstant_R5 - delta(%ecx), CONSTANT
- movdqa .Lconstant_mask32 - delta(%ecx), %xmm3
+ movdqa .Lconstant_R5, CONSTANT
+ movdqa .Lconstant_mask32, %xmm3
#endif
psrldq $0x04, %xmm2
pand %xmm3, %xmm1
@@ -232,7 +227,7 @@ fold_64:
#ifdef __x86_64__
movdqa .Lconstant_RUpoly(%rip), CONSTANT
#else
- movdqa .Lconstant_RUpoly - delta(%ecx), CONSTANT
+ movdqa .Lconstant_RUpoly, CONSTANT
#endif
movdqa %xmm1, %xmm2
pand %xmm3, %xmm1
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