| From 2ffa8b8660a7a17572ae5a398171c8be59985eb3 Mon Sep 17 00:00:00 2001 |
| From: "Gabriel F. T. Gomes" <gftg@linux.vnet.ibm.com> |
| Date: Mon, 25 Jan 2016 10:50:34 -0500 |
| Subject: [PATCH] powerpc: Zero pad using memset in strncpy/stpncpy |
| |
| Call __memset_power8 to pad, with zeros, the remaining bytes in the |
| dest string on __strncpy_power8 and __stpncpy_power8. This improves |
| performance when n is larger than the input string, giving ~30% gain for |
| larger strings without impacting much shorter strings. |
| |
| (cherry picked from commit 72c11b353ede72931cc474c9071d143d9a05c0d7) |
| |
| ChangeLog | 5 ++ |
| sysdeps/powerpc/powerpc64/power8/strncpy.S | 123 +++++++++++++---------------- |
| 2 files changed, 61 insertions(+), 67 deletions(-) |
| |
| diff --git a/ChangeLog b/ChangeLog |
| index 5537fc6..8d0e296 100644 |
| diff --git a/sysdeps/powerpc/powerpc64/power8/strncpy.S b/sysdeps/powerpc/powerpc64/power8/strncpy.S |
| index 5fda953..80136cc 100644 |
| |
| |
| @@ -24,6 +24,8 @@ |
| # define FUNC_NAME strncpy |
| #endif |
| |
| +#define FRAMESIZE (FRAME_MIN_SIZE+48) |
| + |
| /* Implements the function |
| |
| char * [r3] strncpy (char *dest [r3], const char *src [r4], size_t n [r5]) |
| @@ -54,8 +56,7 @@ EALIGN (FUNC_NAME, 4, 0) |
| addi r10,r4,16 |
| rlwinm r9,r4,0,19,19 |
| |
| - /* Since it is a leaf function, save some non-volatile registers on the |
| - protected/red zone. */ |
| + /* Save some non-volatile registers on the stack. */ |
| std r26,-48(r1) |
| std r27,-40(r1) |
| |
| @@ -69,6 +70,14 @@ EALIGN (FUNC_NAME, 4, 0) |
| std r30,-16(r1) |
| std r31,-8(r1) |
| |
| + /* Update CFI. */ |
| + cfi_offset(r26, -48) |
| + cfi_offset(r27, -40) |
| + cfi_offset(r28, -32) |
| + cfi_offset(r29, -24) |
| + cfi_offset(r30, -16) |
| + cfi_offset(r31, -8) |
| + |
| beq cr7,L(unaligned_lt_16) |
| rldicl r9,r4,0,61 |
| subfic r8,r9,8 |
| @@ -144,74 +153,58 @@ L(short_path_loop_end): |
| ld r31,-8(r1) |
| blr |
| |
| - /* This code pads the remainder dest with NULL bytes. The algorithm |
| - calculate the remanining size and issues a doubleword unrolled |
| - loops followed by a byte a byte set. */ |
| + /* This code pads the remainder of dest with NULL bytes. The algorithm |
| + calculates the remaining size and calls memset. */ |
| .align 4 |
| L(zero_pad_start): |
| mr r5,r10 |
| mr r9,r6 |
| L(zero_pad_start_1): |
| - srdi. r8,r5,r3 |
| - mr r10,r9 |
| -#ifdef USE_AS_STPNCPY |
| - mr r3,r9 |
| + /* At this point: |
| + - r5 holds the number of bytes that still have to be written to |
| + dest. |
| + - r9 points to the position, in dest, where the first null byte |
| + will be written. |
| + The above statements are true both when control reaches this label |
| + from a branch or when falling through the previous lines. */ |
| +#ifndef USE_AS_STPNCPY |
| + mr r30,r3 /* Save the return value of strncpy. */ |
| +#endif |
| + /* Prepare the call to memset. */ |
| + mr r3,r9 /* Pointer to the area to be zero-filled. */ |
| + li r4,0 /* Byte to be written (zero). */ |
| + |
| + /* We delayed the creation of the stack frame, as well as the saving of |
| + the link register, because only at this point, we are sure that |
| + doing so is actually needed. */ |
| + |
| + /* Save the link register. */ |
| + mflr r0 |
| + std r0,16(r1) |
| + cfi_offset(lr, 16) |
| + |
| + /* Create the stack frame. */ |
| + stdu r1,-FRAMESIZE(r1) |
| + cfi_adjust_cfa_offset(FRAMESIZE) |
| + |
| + bl __memset_power8 |
| + nop |
| + |
| + /* Restore the stack frame. */ |
| + addi r1,r1,FRAMESIZE |
| + cfi_adjust_cfa_offset(-FRAMESIZE) |
| + /* Restore the link register. */ |
| + ld r0,16(r1) |
| + mtlr r0 |
| + |
| +#ifndef USE_AS_STPNCPY |
| + mr r3,r30 /* Restore the return value of strncpy, i.e.: |
| + dest. For stpncpy, the return value is the |
| + same as return value of memset. */ |
| #endif |
| - beq- cr0,L(zero_pad_loop_b_start) |
| - cmpldi cr7,r8,1 |
| - li cr7,0 |
| - std r7,0(r9) |
| - beq cr7,L(zero_pad_loop_b_prepare) |
| - addic. r8,r8,-2 |
| - addi r10,r9,r16 |
| - std r7,8(r9) |
| - beq cr0,L(zero_pad_loop_dw_2) |
| - std r7,16(r9) |
| - li r9,0 |
| - b L(zero_pad_loop_dw_1) |
| - |
| - .align 4 |
| -L(zero_pad_loop_dw): |
| - addi r10,r10,16 |
| - std r9,-8(r10) |
| - beq cr0,L(zero_pad_loop_dw_2) |
| - std r9,0(r10) |
| -L(zero_pad_loop_dw_1): |
| - cmpldi cr7,r8,1 |
| - std r9,0(r10) |
| - addic. r8,r8,-2 |
| - bne cr7,L(zero_pad_loop_dw) |
| - addi r10,r10,8 |
| -L(zero_pad_loop_dw_2): |
| - rldicl r5,r5,0,61 |
| -L(zero_pad_loop_b_start): |
| - cmpdi cr7,r5,0 |
| - addi r5,r5,-1 |
| - addi r9,r10,-1 |
| - add r10,r10,5 |
| - subf r10,r9,r10 |
| - li r8,0 |
| - beq- cr7,L(short_path_loop_end) |
| - |
| - /* Write remaining 1-8 bytes. */ |
| - .align 4 |
| - addi r9,r9,1 |
| - mtocrf 0x1,r10 |
| - bf 29,4f |
| - stw r8,0(r9) |
| - addi r9,r9,4 |
| - |
| - .align 4 |
| -4: bf 30,2f |
| - sth r8,0(r9) |
| - addi r9,r9,2 |
| - |
| - .align 4 |
| -2: bf 31,1f |
| - stb r8,0(r9) |
| |
| - /* Restore non-volatile registers. */ |
| -1: ld r26,-48(r1) |
| + /* Restore non-volatile registers and return. */ |
| + ld r26,-48(r1) |
| ld r27,-40(r1) |
| ld r28,-32(r1) |
| ld r29,-24(r1) |
| @@ -407,10 +400,6 @@ L(short_path_prepare_2_3): |
| mr r4,r28 |
| mr r9,r29 |
| b L(short_path_2) |
| -L(zero_pad_loop_b_prepare): |
| - addi r10,r9,8 |
| - rldicl r5,r5,0,61 |
| - b L(zero_pad_loop_b_start) |
| L(zero_pad_start_prepare_1): |
| mr r5,r6 |
| mr r9,r8 |
| -- |
| 2.1.0 |
| |