[PATCH v2] riscv: lib: Check if output in asm goto supported

Charlie Jenkins
2024-01-18T22:37:07Z

The output field of an asm goto statement is not supported by all
compilers. If it is not supported, fallback to the non-optimized code.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Fixes: a04c192eabfb ("riscv: Add checksum library")
---
The OutputOperands field for asm goto statements is only supported
starting from GCC 11. Split the asm goto to remove the use of this
feature.
---
Changes in v2:
- Use CC_HAS_ASM_GOTO_TIED_OUTPUT
- Link to v1: https://lore.kernel.org/r/20240118-csum_remove_output_operands_asm_goto-v1-1-47c672bb9d4b@rivosinc.com
---
arch/riscv/lib/csum.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/riscv/lib/csum.c b/arch/riscv/lib/csum.c
index 06ce8e7250d9..af3df5274ccb 100644
--- a/arch/riscv/lib/csum.c
+++ b/arch/riscv/lib/csum.c
@@ -156,6 +156,7 @@ do_csum_with_alignment(const unsigned char *buff, int len)
end = (const unsigned long *)(buff + len);
csum = do_csum_common(ptr, end, data);

+#ifdef CC_HAS_ASM_GOTO_TIED_OUTPUT
/*
* Zbb support saves 6 instructions, so not worth checking without
* alternatives if supported
@@ -214,6 +215,7 @@ do_csum_with_alignment(const unsigned char *buff, int len)
return csum >> 16;
}
no_zbb:
+#endif /* CC_HAS_ASM_GOTO_TIED_OUTPUT */
#ifndef CONFIG_32BIT
csum += ror64(csum, 32);
csum >>= 32;

---
base-commit: 080c4324fa5e81ff3780206a138223abfb57a68e
change-id: 20240118-csum_remove_output_operands_asm_goto-49922c141ce7
--
- Charlie