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@xxxxxxxxxx> --- 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
