linux-kernel - [PATCH v2 3/9] LoongArch: Prepare for assemblers with proper FCSR class support

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Message-Id: <20230624184055.3000636-4-kernel@xen0n.name>
Date:   Sun, 25 Jun 2023 02:40:49 +0800
From:   WANG Xuerui <kernel@...0n.name>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     WANG Rui <wangrui@...ngson.cn>, Xi Ruoyao <xry111@...111.site>,
        loongarch@...ts.linux.dev, linux-kbuild@...r.kernel.org,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        WANG Xuerui <git@...0n.name>
Subject: [PATCH v2 3/9] LoongArch: Prepare for assemblers with proper FCSR class support

From: WANG Xuerui <git@...0n.name>

The GNU assembler (as of 2.40) mis-treats FCSR operands as GPRs, but
the LLVM IAS does not. Probe for this and refer to FCSRs as "$fcsrNN"
if support is present.

Signed-off-by: WANG Xuerui <git@...0n.name>
---
 arch/loongarch/Kconfig                 | 3 +++
 arch/loongarch/include/asm/fpregdef.h  | 7 +++++++
 arch/loongarch/include/asm/loongarch.h | 9 ++++++++-
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 743d87655742..ac3564935281 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -242,6 +242,9 @@ config SCHED_OMIT_FRAME_POINTER
 config AS_HAS_EXPLICIT_RELOCS
 	def_bool $(as-instr,x:pcalau12i \$t0$(comma)%pc_hi20(x))
 
+config AS_HAS_FCSR_CLASS
+	def_bool $(as-instr,x:movfcsr2gr \$t0$(comma)\$fcsr0)
+
 config CC_HAS_LSX_EXTENSION
 	def_bool $(cc-option,-mlsx)
 
diff --git a/arch/loongarch/include/asm/fpregdef.h b/arch/loongarch/include/asm/fpregdef.h
index b6be527831dd..3eb7ff9e1d8e 100644
--- a/arch/loongarch/include/asm/fpregdef.h
+++ b/arch/loongarch/include/asm/fpregdef.h
@@ -40,6 +40,12 @@
 #define fs6	$f30
 #define fs7	$f31
 
+#ifdef CONFIG_AS_HAS_FCSR_CLASS
+#define fcsr0	$fcsr0
+#define fcsr1	$fcsr1
+#define fcsr2	$fcsr2
+#define fcsr3	$fcsr3
+#else
 /*
  * Current binutils expects *GPRs* at FCSR position for the FCSR
  * operation instructions, so define aliases for those used.
@@ -48,5 +54,6 @@
 #define fcsr1	$r1
 #define fcsr2	$r2
 #define fcsr3	$r3
+#endif
 
 #endif /* _ASM_FPREGDEF_H */
diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
index ac83e60c60d1..ff4482fd8ad7 100644
--- a/arch/loongarch/include/asm/loongarch.h
+++ b/arch/loongarch/include/asm/loongarch.h
@@ -1445,11 +1445,18 @@ __BUILD_CSR_OP(tlbidx)
 #define EXCCODE_INT_START	64
 #define EXCCODE_INT_END		(EXCCODE_INT_START + EXCCODE_INT_NUM - 1)
 
-/* FPU register names */
+/* FPU Status Register Names */
+#ifdef CONFIG_AS_HAS_FCSR_CLASS
+#define LOONGARCH_FCSR0	$fcsr0
+#define LOONGARCH_FCSR1	$fcsr1
+#define LOONGARCH_FCSR2	$fcsr2
+#define LOONGARCH_FCSR3	$fcsr3
+#else
 #define LOONGARCH_FCSR0	$r0
 #define LOONGARCH_FCSR1	$r1
 #define LOONGARCH_FCSR2	$r2
 #define LOONGARCH_FCSR3	$r3
+#endif
 
 /* FPU Status Register Values */
 #define FPU_CSR_RSVD	0xe0e0fce0
-- 
2.40.0