linux-kernel - [PATCH v2 1/2] ARM: drop WASM to work around LLVM issue

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Date:   Mon, 18 Mar 2019 00:05:26 +0100
From:   Stefan Agner <stefan@...er.ch>
To:     linux@...linux.org.uk
Cc:     robin.murphy@....com, will.deacon@....com, ndesaulniers@...gle.com,
        natechancellor@...il.com, arnd@...db.de, ard.biesheuvel@...aro.org,
        nicolas.pitre@...aro.org, thierry.reding@...il.com,
        julien.thierry@....com, mark.rutland@....com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Stefan Agner <stefan@...er.ch>
Subject: [PATCH v2 1/2] ARM: drop WASM to work around LLVM issue

Currently LLVM's integrated assembler does not recognize .w form
of the pld instructions (LLVM Bug 40972 [0]):

  ./arch/arm/include/asm/processor.h:133:5: error: invalid instruction
                          "pldw.w\t%a0 \n"
                           ^
  <inline asm>:2:1: note: instantiated into assembly here
  pldw.w  [r0]
  ^
  1 error generated.

The W macro for generating wide instructions when targeting Thumb-2
is not strictly required for the preload data instructions (pld, pldw)
since they are only available as wide instructions. The GNU assembler
works with or without the .w appended when compiling an Thumb-2 kernel.

Drop the macro to work around LLVM Bug 40972 issue.

[0] https://bugs.llvm.org/show_bug.cgi?id=40972

Signed-off-by: Stefan Agner <stefan@...er.ch>
---
Changes in v2:
- Reword commit message to reflect the fact that this is a work around
  for LLVM.

 arch/arm/include/asm/processor.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 57fe73ea0f72..5d06f75ffad4 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -135,8 +135,8 @@ static inline void prefetchw(const void *ptr)
 	__asm__ __volatile__(
 		".arch_extension	mp\n"
 		__ALT_SMP_ASM(
-			WASM(pldw)		"\t%a0",
-			WASM(pld)		"\t%a0"
+			"pldw\t%a0",
+			"pld\t%a0"
 		)
 		:: "p" (ptr));
 }
-- 
2.21.0