From: Siarhei Volkau <lis8215@gmail.com>
To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
Siarhei Volkau <lis8215@gmail.com>
Cc: Paul Cercueil <paul@crapouillou.net>
Subject: [PATCH] MIPS: Take in account load hazards for HI/LO restoring
Date: Thu, 12 Oct 2023 19:20:27 +0300 [thread overview]
Message-ID: <20231012162027.3411684-1-lis8215@gmail.com> (raw)
MIPS CPUs usually have 1 to 4 cycles load hazards, thus doing load
and right after move to HI/LO will usually stall the pipeline for
significant amount of time. Let's take it into account and separate
loads and mthi/lo in instruction sequence.
The patch uses t6 and t7 registers as temporaries in addition to t8.
The patch tries to deal with SmartMIPS, but I know little about and
haven't tested it.
Signed-off-by: Siarhei Volkau <lis8215@gmail.com>
---
arch/mips/include/asm/stackframe.h | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/arch/mips/include/asm/stackframe.h b/arch/mips/include/asm/stackframe.h
index a8705aef47e1..3821d91b00fd 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -308,17 +308,11 @@
jal octeon_mult_restore
#endif
#ifdef CONFIG_CPU_HAS_SMARTMIPS
- LONG_L $24, PT_ACX(sp)
- mtlhx $24
- LONG_L $24, PT_HI(sp)
- mtlhx $24
- LONG_L $24, PT_LO(sp)
- mtlhx $24
-#elif !defined(CONFIG_CPU_MIPSR6)
+ LONG_L $14, PT_ACX(sp)
+#endif
+#if defined(CONFIG_CPU_HAS_SMARTMIPS) || !defined(CONFIG_CPU_MIPSR6)
LONG_L $24, PT_LO(sp)
- mtlo $24
- LONG_L $24, PT_HI(sp)
- mthi $24
+ LONG_L $15, PT_HI(sp)
#endif
#ifdef CONFIG_32BIT
cfi_ld $8, PT_R8, \docfi
@@ -327,6 +321,14 @@
cfi_ld $10, PT_R10, \docfi
cfi_ld $11, PT_R11, \docfi
cfi_ld $12, PT_R12, \docfi
+#ifdef CONFIG_CPU_HAS_SMARTMIPS
+ mtlhx $14
+ mtlhx $15
+ mtlhx $24
+#elif !defined(CONFIG_CPU_MIPSR6)
+ mtlo $24
+ mthi $15
+#endif
cfi_ld $13, PT_R13, \docfi
cfi_ld $14, PT_R14, \docfi
cfi_ld $15, PT_R15, \docfi
--
2.41.0
next reply other threads:[~2023-10-12 16:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-12 16:20 Siarhei Volkau [this message]
2024-04-29 6:42 ` [PATCH] MIPS: Take in account load hazards for HI/LO restoring Siarhei Volkau
2024-04-29 8:18 ` Thomas Bogendoerfer
2024-04-29 8:30 ` Thomas Bogendoerfer
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