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From: Charlie Jenkins <charlie@rivosinc.com>
Date: Thu, 18 Jan 2024 13:53:59 -0800
Subject: [PATCH] riscv: lib: Support csum on GCC <11
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Message-Id: <20240118-csum_remove_output_operands_asm_goto-v1-1-47c672bb9d4b@rivosinc.com>
To: Paul Walmsley <paul.walmsley@sifive.com>, 
 Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, 
 Charlie Jenkins <charlie@rivosinc.com>

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.

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.
---
 arch/riscv/lib/csum.c | 42 ++++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/arch/riscv/lib/csum.c b/arch/riscv/lib/csum.c
index 06ce8e7250d9..23be289f52b6 100644
--- a/arch/riscv/lib/csum.c
+++ b/arch/riscv/lib/csum.c
@@ -177,22 +177,35 @@ do_csum_with_alignment(const unsigned char *buff, int len)
 				  : no_zbb);
 
 #ifdef CONFIG_32BIT
-		asm_volatile_goto(".option push			\n\
+		/*
+		 * OutputOperands in asm goto is not supported until GCC 11, so
+		 * this asm has to be split to be compatible.
+		 */
+		asm (".option push				\n\
 		.option arch,+zbb				\n\
 			rori	%[fold_temp], %[csum], 16	\n\
 			andi	%[offset], %[offset], 1		\n\
 			add	%[csum], %[fold_temp], %[csum]	\n\
-			beq	%[offset], zero, %l[end]	\n\
-			rev8	%[csum], %[csum]		\n\
 		.option pop"
 			: [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
-			: [offset] "r" (offset)
-			:
-			: end);
+			: [offset] "r" (offset));
+
+		if (offset == 0)
+			goto end;
+
+		asm (".option push				\n\
+		.option arch, +zbb				\n\
+			rev8	%[csum], %[csum]		\n\
+		.option pop"
+			: [csum] "+r" (csum));
 
 		return (unsigned short)csum;
 #else /* !CONFIG_32BIT */
-		asm_volatile_goto(".option push			\n\
+		/*
+		 * OutputOperands in asm goto is not supported until GCC 11, so
+		 * this asm has to be split to be compatible.
+		 */
+		asm (".option push				\n\
 		.option arch,+zbb				\n\
 			rori	%[fold_temp], %[csum], 32	\n\
 			add	%[csum], %[fold_temp], %[csum]	\n\
@@ -200,13 +213,18 @@ do_csum_with_alignment(const unsigned char *buff, int len)
 			roriw	%[fold_temp], %[csum], 16	\n\
 			addw	%[csum], %[fold_temp], %[csum]	\n\
 			andi	%[offset], %[offset], 1		\n\
-			beq	%[offset], zero, %l[end]	\n\
-			rev8	%[csum], %[csum]		\n\
 		.option pop"
 			: [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)
-			: [offset] "r" (offset)
-			:
-			: end);
+			: [offset] "r" (offset));
+
+		if (offset == 0)
+			goto end;
+
+		asm (".option push				\n\
+		.option arch, +zbb				\n\
+			rev8	%[csum], %[csum]		\n\
+		.option pop"
+			: [csum] "+r" (csum));
 
 		return (csum << 16) >> 48;
 #endif /* !CONFIG_32BIT */

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