llvm.lists.linux.dev archive mirror
 help / color / mirror / Atom feed
From: Jiaxun Yang <jiaxun.yang@flygoat.com>
To: linux-mips@vger.kernel.org
Cc: tsbogend@alpha.franken.de, nathan@kernel.org,
	llvm@lists.linux.dev, Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: [PATCH] MIPS: Workaround clang inline compat branch issue
Date: Sat, 25 Feb 2023 21:45:00 +0000	[thread overview]
Message-ID: <20230225214500.7446-1-jiaxun.yang@flygoat.com> (raw)

Clang is unable to handle the situation that a chunk of inline
assembly ends with a compat branch instruction and then compiler
generates another control transfer instruction immediately after
this compat branch. The later instruction will end up in forbidden
slot and cause exception.

Workaround by add a option to control the use of compact branch.
Currently it's selected by CC_IS_CLANG and hopefully we can change
it to a version check in future if clang manages to fix it.

Fix boot on boston board.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
 arch/mips/Kconfig           | 3 +++
 arch/mips/include/asm/asm.h | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 37072e15b263..adf2c5a0bdba 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -3206,6 +3206,9 @@ config CC_HAS_MNO_BRANCH_LIKELY
 	def_bool y
 	depends on $(cc-option,-mno-branch-likely)
 
+config CC_HAS_BROKEN_INLINE_COMPAT_BRANCH
+	def_bool y if CC_IS_CLANG
+
 menu "Power management options"
 
 config ARCH_HIBERNATION_POSSIBLE
diff --git a/arch/mips/include/asm/asm.h b/arch/mips/include/asm/asm.h
index 336ac9b65235..2e99450f4228 100644
--- a/arch/mips/include/asm/asm.h
+++ b/arch/mips/include/asm/asm.h
@@ -336,7 +336,7 @@ symbol		=	value
  */
 #ifdef CONFIG_WAR_R10000_LLSC
 # define SC_BEQZ	beqzl
-#elif MIPS_ISA_REV >= 6
+#elif !defined(CONFIG_CC_HAS_BROKEN_INLINE_COMPAT_BRANCH) && MIPS_ISA_REV >= 6
 # define SC_BEQZ	beqzc
 #else
 # define SC_BEQZ	beqz
-- 
2.37.1 (Apple Git-137.1)


             reply	other threads:[~2023-02-25 21:45 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-25 21:45 Jiaxun Yang [this message]
2023-02-27 18:19 ` [PATCH] MIPS: Workaround clang inline compat branch issue Nick Desaulniers

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20230225214500.7446-1-jiaxun.yang@flygoat.com \
    --to=jiaxun.yang@flygoat.com \
    --cc=linux-mips@vger.kernel.org \
    --cc=llvm@lists.linux.dev \
    --cc=nathan@kernel.org \
    --cc=tsbogend@alpha.franken.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).