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