[PATCH v3] MIPS: Workaround clang inline compat branch issue

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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.

Link: https://github.com/llvm/llvm-project/issues/61045
Signed-off-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
Acked-by: Nathan Chancellor <nathan@xxxxxxxxxx>
---
v2: Add Link tag to LLVM bug
v3: Docuement issue link in Kconfig as well
---
 arch/mips/Kconfig           | 4 ++++
 arch/mips/include/asm/asm.h | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 37072e15b263..c8b878aa690f 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -3206,6 +3206,10 @@ config CC_HAS_MNO_BRANCH_LIKELY
 	def_bool y
 	depends on $(cc-option,-mno-branch-likely)
 
+# https://github.com/llvm/llvm-project/issues/61045
+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)




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