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[PATCH] MIPS: Reorder operations in stackframe.h for better scheduling (

To: David Daney <ddaney@caviumnetworks.com>
Subject: [PATCH] MIPS: Reorder operations in stackframe.h for better scheduling (v2)
From: David Daney <ddaney@caviumnetworks.com>
Date: Tue, 18 Nov 2008 15:54:10 -0800
Cc: linux-mips <linux-mips@linux-mips.org>
In-reply-to: <49235080.3070202@caviumnetworks.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <49235080.3070202@caviumnetworks.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.16 (X11/20080723)
David Daney wrote:
Reorder PT ops to avoid pipeline stalls.

--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -51,9 +51,6 @@
        LONG_S    v1, PT_ACX(sp)
#else
        mfhi    v1
-        LONG_S    v1, PT_HI(sp)
-        mflo    v1
-        LONG_S    v1, PT_LO(sp)
#endif
#ifdef CONFIG_32BIT
        LONG_S    $8, PT_R8(sp)
@@ -62,10 +59,13 @@
        LONG_S    $10, PT_R10(sp)
        LONG_S    $11, PT_R11(sp)
        LONG_S    $12, PT_R12(sp)
+        LONG_S    v1, PT_HI(sp)
+        mflo    v1
        LONG_S    $13, PT_R13(sp)
        LONG_S    $14, PT_R14(sp)
        LONG_S    $15, PT_R15(sp)
        LONG_S    $24, PT_R24(sp)
+        LONG_S    v1, PT_LO(sp)
        .endm

Those changes escaped the CONFIG_CPU_HAS_SMARTMIPS, please try this
version instead:

MIPS: Reorder operations in stackframe.h for better scheduling

Reorder PT ops to avoid pipeline stalls.

Signed-off-by: Tomaso Paoletti <tpaoletti@caviumnetworks.com>
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
---
arch/mips/include/asm/stackframe.h |   20 ++++++++++++--------
1 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/mips/include/asm/stackframe.h 
b/arch/mips/include/asm/stackframe.h
index db0fa7b..dd7e220 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -51,9 +51,6 @@
                LONG_S  v1, PT_ACX(sp)
#else
                mfhi    v1
-               LONG_S  v1, PT_HI(sp)
-               mflo    v1
-               LONG_S  v1, PT_LO(sp)
#endif
#ifdef CONFIG_32BIT
                LONG_S  $8, PT_R8(sp)
@@ -62,10 +59,17 @@
                LONG_S  $10, PT_R10(sp)
                LONG_S  $11, PT_R11(sp)
                LONG_S  $12, PT_R12(sp)
+#ifndef CONFIG_CPU_HAS_SMARTMIPS
+               LONG_S  v1, PT_HI(sp)
+               mflo    v1
+#endif
                LONG_S  $13, PT_R13(sp)
                LONG_S  $14, PT_R14(sp)
                LONG_S  $15, PT_R15(sp)
                LONG_S  $24, PT_R24(sp)
+#ifndef CONFIG_CPU_HAS_SMARTMIPS
+               LONG_S  v1, PT_LO(sp)
+#endif
                .endm

                .macro  SAVE_STATIC
@@ -166,7 +170,6 @@
                LONG_S  $0, PT_R0(sp)
                mfc0    v1, CP0_STATUS
                LONG_S  $2, PT_R2(sp)
-               LONG_S  v1, PT_STATUS(sp)
#ifdef CONFIG_MIPS_MT_SMTC
                /*
                 * Ideally, these instructions would be shuffled in
@@ -178,19 +181,20 @@
                LONG_S  v1, PT_TCSTATUS(sp)
#endif /* CONFIG_MIPS_MT_SMTC */
                LONG_S  $4, PT_R4(sp)
-               mfc0    v1, CP0_CAUSE
                LONG_S  $5, PT_R5(sp)
-               LONG_S  v1, PT_CAUSE(sp)
+               LONG_S  v1, PT_STATUS(sp)
+               mfc0    v1, CP0_CAUSE
                LONG_S  $6, PT_R6(sp)
-               MFC0    v1, CP0_EPC
                LONG_S  $7, PT_R7(sp)
+               LONG_S  v1, PT_CAUSE(sp)
+               MFC0    v1, CP0_EPC
#ifdef CONFIG_64BIT
                LONG_S  $8, PT_R8(sp)
                LONG_S  $9, PT_R9(sp)
#endif
-               LONG_S  v1, PT_EPC(sp)
                LONG_S  $25, PT_R25(sp)
                LONG_S  $28, PT_R28(sp)
                LONG_S  $31, PT_R31(sp)
+               LONG_S  v1, PT_EPC(sp)
                ori     $28, sp, _THREAD_MASK
                xori    $28, _THREAD_MASK

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