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From 561857f53a543684862c2b6d2308bc13affa2a18 Mon Sep 17 00:00:00 2001
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From: Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
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Date: Tue, 18 Aug 2015 22:40:56 +0530
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Subject: [PATCH] powerpc: Handle worstcase behavior in strstr() for POWER7
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Instead of checking needle length, constant 'n' number of comparisons
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is checked to fall back to default implementation. This patch is tested
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on powerpc64 and powerpc64le.
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2015-08-25 Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
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* sysdeps/powerpc/powerpc64/power7/strstr.S: Handle worst case.
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(cherry picked from commit fe7faec3e56a8dd64f78023a2f4a74fc8d42e79f)
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---
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ChangeLog | 4 ++++
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sysdeps/powerpc/powerpc64/power7/strstr.S | 22 +++++++++++++++-------
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2 files changed, 19 insertions(+), 7 deletions(-)
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diff --git a/ChangeLog b/ChangeLog
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index cf95a84..5cbd6d6 100644
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diff --git a/sysdeps/powerpc/powerpc64/power7/strstr.S b/sysdeps/powerpc/powerpc64/power7/strstr.S
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index bfb0c49..fb3c810 100644
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--- a/sysdeps/powerpc/powerpc64/power7/strstr.S
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+++ b/sysdeps/powerpc/powerpc64/power7/strstr.S
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@@ -23,6 +23,8 @@
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/* The performance gain is obtained using aligned memory access, load
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* doubleword and usage of cmpb instruction for quicker comparison. */
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+#define ITERATIONS 64
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+
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#ifndef STRLEN
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/* For builds with no IFUNC support, local calls should be made to internal
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GLIBC symbol (created by libc_hidden_builtin_def). */
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@@ -62,6 +64,8 @@ EALIGN (strstr, 4, 0)
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cfi_offset(r30, -16)
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std r29, -24(r1) /* Save callers register r29. */
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cfi_offset(r29, -24)
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+ std r28, -32(r1) /* Save callers register r28. */
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+ cfi_offset(r28, -32)
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std r0, 16(r1) /* Store the link register. */
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cfi_offset(lr, 16)
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stdu r1, -FRAMESIZE(r1) /* Create the stack frame. */
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@@ -69,7 +73,6 @@ EALIGN (strstr, 4, 0)
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dcbt 0, r3
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dcbt 0, r4
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-
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cmpdi cr7, r3, 0
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beq cr7, L(retnull)
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cmpdi cr7, r4, 0
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@@ -84,10 +87,6 @@ EALIGN (strstr, 4, 0)
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cmpdi cr7, r3, 0 /* If search str is null. */
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beq cr7, L(ret_r3)
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- /* Call __strstr_ppc if needle len > 2048 */
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- cmpdi cr7, r3, 2048
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- bgt cr7, L(default)
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-
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mr r31, r3
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mr r4, r3
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mr r3, r29
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@@ -105,7 +104,8 @@ EALIGN (strstr, 4, 0)
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/* If first char of search str is not present. */
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cmpdi cr7, r3, 0
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ble cr7, L(end)
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-
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+ /* Reg r28 is used to count the number of iterations. */
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+ li r28, 0
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rldicl r8, r3, 0, 52 /* Page cross check. */
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cmpldi cr7, r8, 4096-16
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bgt cr7, L(bytebybyte)
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@@ -324,6 +324,10 @@ L(return4):
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.align 4
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L(begin):
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mr r3, r8
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+ /* When our iterations exceed ITERATIONS,fall back to default. */
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+ addi r28, r28, 1
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+ cmpdi cr7, r28, ITERATIONS
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+ beq cr7, L(default)
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lbz r4, 0(r30)
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bl STRCHR
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nop
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@@ -423,6 +427,10 @@ L(nextbyte):
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cmpdi cr7, r9, -1
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beq cr7, L(end)
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addi r3, r4, 1
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+ /* When our iterations exceed ITERATIONS,fall back to default. */
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+ addi r28, r28, 1
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+ cmpdi cr7, r28, ITERATIONS
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+ beq cr7, L(default)
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lbz r4, 0(r30)
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bl STRCHR
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nop
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@@ -490,7 +498,6 @@ L(retnull):
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.align 4
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L(default):
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- mr r3, r29
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mr r4, r30
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bl __strstr_ppc
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nop
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@@ -500,6 +507,7 @@ L(end):
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addi r1, r1, FRAMESIZE /* Restore stack pointer. */
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cfi_adjust_cfa_offset(-FRAMESIZE)
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ld r0, 16(r1) /* Restore the saved link register. */
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+ ld r28, -32(r1) /* Restore callers save register r28. */
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ld r29, -24(r1) /* Restore callers save register r29. */
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ld r30, -16(r1) /* Restore callers save register r30. */
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ld r31, -8(r1) /* Restore callers save register r31. */
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--
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2.1.0
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