runtime: save and restore fcc registers in async preempt on loong64

During the context switch of goroutine scheduling, the value of the
fcc0 register needs to be saved on the stack.

Fixs #59000.

Change-Id: Ie80dbae738f60df6c11a3fe31fc57de817d76afc
Reviewed-on: https://go-review.googlesource.com/c/go/+/475577
Reviewed-by: Cherry Mui <[email protected]>
Run-TryBot: Cherry Mui <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: abner chenc <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: WANG Xuerui <[email protected]>

Author: Huang Qiqi

src/runtime/mkpreempt.go

@@ -481,6 +481,12 @@ func genLoong64() {
 		l.add(movf, reg, regsize)
 	}
 
+	// save/restore FCC0
+	l.addSpecial(
+		mov+" FCC0, R4\n"+mov+" R4, %d(R3)",
+		mov+" %d(R3), R4\n"+mov+" R4, FCC0",
+		regsize)
+
 	// allocate frame, save PC of interrupted instruction (in LR)
 	p(mov+" R1, -%d(R3)", l.stack)
 	p(sub+" $%d, R3", l.stack)

src/runtime/preempt_loong64.s

@@ -4,8 +4,8 @@
 #include "textflag.h"
 
 TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
-	MOVV R1, -472(R3)
-	SUBV $472, R3
+	MOVV R1, -480(R3)
+	SUBV $480, R3
 	MOVV R4, 8(R3)
 	MOVV R5, 16(R3)
 	MOVV R6, 24(R3)
@@ -64,7 +64,11 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	MOVD F29, 448(R3)
 	MOVD F30, 456(R3)
 	MOVD F31, 464(R3)
+	MOVV FCC0, R4
+	MOVV R4, 472(R3)
 	CALL ·asyncPreempt2(SB)
+	MOVV 472(R3), R4
+	MOVV R4, FCC0
 	MOVD 464(R3), F31
 	MOVD 456(R3), F30
 	MOVD 448(R3), F29
@@ -123,7 +127,7 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	MOVV 24(R3), R6
 	MOVV 16(R3), R5
 	MOVV 8(R3), R4
-	MOVV 472(R3), R1
+	MOVV 480(R3), R1
 	MOVV (R3), R30
-	ADDV $480, R3
+	ADDV $488, R3
 	JMP (R30)