runtime/internal/syscall: use ABIInternal for Syscall6 on loong64

Updates #40724

Co-authored-by: Xiaolin Zhao <[email protected]>
Change-Id: Ifcc2de35a797fd987a10f564206b14b54d736d1d
Reviewed-on: https://go-review.googlesource.com/c/go/+/521789
Auto-Submit: David Chase <[email protected]>
Reviewed-by: Meidan Li <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Run-TryBot: David Chase <[email protected]>
Reviewed-by: David Chase <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: 2 people

src/runtime/internal/syscall/asm_linux_loong64.s

@@ -5,25 +5,64 @@
 #include "textflag.h"
 
 // func Syscall6(num, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, errno uintptr)
-TEXT ·Syscall6(SB),NOSPLIT,$0-80
+//
+// We need to convert to the syscall ABI.
+//
+// arg | ABIInternal | Syscall
+// ---------------------------
+// num | R4          | R11
+// a1  | R5          | R4
+// a2  | R6          | R5
+// a3  | R7          | R6
+// a4  | R8          | R7
+// a5  | R9          | R8
+// a6  | R10         | R9
+//
+// r1  | R4          | R4
+// r2  | R5          | R5
+// err | R6          | part of R4
+TEXT ·Syscall6<ABIInternal>(SB),NOSPLIT,$0-80
+#ifdef GOEXPERIMENT_regabiargs
+	MOVV	R4, R11  // syscall entry
+	MOVV	R5, R4
+	MOVV	R6, R5
+	MOVV	R7, R6
+	MOVV	R8, R7
+	MOVV	R9, R8
+	MOVV	R10, R9
+#else
 	MOVV	num+0(FP), R11  // syscall entry
 	MOVV	a1+8(FP), R4
 	MOVV	a2+16(FP), R5
 	MOVV	a3+24(FP), R6
 	MOVV	a4+32(FP), R7
 	MOVV	a5+40(FP), R8
 	MOVV	a6+48(FP), R9
+#endif
 	SYSCALL
+#ifdef GOEXPERIMENT_regabiargs
+	MOVV	R0, R5      // r2 is not used. Always set to 0.
+	MOVW	$-4096, R12
+	BGEU	R12, R4, ok
+	SUBVU	R4, R0, R6  // errno
+	MOVV	$-1, R4     // r1
+#else
 	MOVW	$-4096, R12
 	BGEU	R12, R4, ok
 	MOVV	$-1, R12
 	MOVV	R12, r1+56(FP)
 	MOVV	R0, r2+64(FP)
 	SUBVU	R4, R0, R4
 	MOVV	R4, errno+72(FP)
+#endif
 	RET
 ok:
+#ifdef GOEXPERIMENT_regabiargs
+	// r1 already in R4
+	MOVV	R0, R6     // errno
+#else
 	MOVV	R4, r1+56(FP)
 	MOVV	R0, r2+64(FP)	// r2 is not used. Always set to 0.
 	MOVV	R0, errno+72(FP)
+#endif
 	RET