reflect, runtime: add reflect support for regabi on riscv64

This CL adds regabi support needed for reflect and reimplement
of CL 360994, which is reverted.

Change-Id: I140673f09109dd9f72eff70aad64c0aa00d6857a
Reviewed-on: https://go-review.googlesource.com/c/go/+/396077
Reviewed-by: Cherry Mui <cherryyz@google.com>
Trust: mzh <mzh@golangcn.org>

2 files changed, 48 insertions, 9 deletions

diff --git a/src/reflect/asm_riscv64.s b/src/reflect/asm_riscv64.s
index e707112277..1200b4d08e 100644
--- a/src/reflect/asm_riscv64.s
+++ b/src/reflect/asm_riscv64.s
@@ -5,34 +5,72 @@
 #include "textflag.h"
 #include "funcdata.h"
 
+// The frames of each of the two functions below contain two locals, at offsets
+// that are known to the runtime.
+//
+// The first local is a bool called retValid with a whole pointer-word reserved
+// for it on the stack. The purpose of this word is so that the runtime knows
+// whether the stack-allocated return space contains valid values for stack
+// scanning.
+//
+// The second local is an abi.RegArgs value whose offset is also known to the
+// runtime, so that a stack map for it can be constructed, since it contains
+// pointers visible to the GC.
+#define LOCAL_RETVALID 40
+#define LOCAL_REGARGS 48
+
+// The frame size of the functions below is
+// 32 (args of callReflect/callMethod) + (8 bool with padding) + 392 (abi.RegArgs) = 432.
+
 // makeFuncStub is the code half of the function returned by MakeFunc.
 // See the comment on the declaration of makeFuncStub in makefunc.go
 // for more details.
 // No arg size here, runtime pulls arg map out of the func value.
-TEXT ·makeFuncStub(SB),(NOSPLIT|WRAPPER),$40
+TEXT ·makeFuncStub(SB),(NOSPLIT|WRAPPER),$432
 	NO_LOCAL_POINTERS
+	ADD	$LOCAL_REGARGS, SP, X25 // spillArgs using X25
+	CALL	runtime·spillArgs(SB)
+	MOV	CTXT, 32(SP) // save CTXT > args of moveMakeFuncArgPtrs < LOCAL_REGARGS
+	MOV	CTXT, 8(SP)
+	MOV	X25, 16(SP)
+	CALL	·moveMakeFuncArgPtrs(SB)
+	MOV	32(SP), CTXT // restore CTXT
+
 	MOV	CTXT, 8(SP)
 	MOV	$argframe+0(FP), T0
 	MOV	T0, 16(SP)
-	ADD	$40, SP, T1
+	MOV	ZERO, LOCAL_RETVALID(SP)
+	ADD	$LOCAL_RETVALID, SP, T1
 	MOV	T1, 24(SP)
-	MOV	ZERO, 32(SP)
-	MOVB	ZERO, 40(SP)
+	ADD	$LOCAL_REGARGS, SP, T1
+	MOV	T1, 32(SP)
 	CALL	·callReflect(SB)
+	ADD	$LOCAL_REGARGS, SP, X25 // unspillArgs using X25
+	CALL	runtime·unspillArgs(SB)
 	RET
 
 // methodValueCall is the code half of the function returned by makeMethodValue.
 // See the comment on the declaration of methodValueCall in makefunc.go
 // for more details.
 // No arg size here; runtime pulls arg map out of the func value.
-TEXT ·methodValueCall(SB),(NOSPLIT|WRAPPER),$40
+TEXT ·methodValueCall(SB),(NOSPLIT|WRAPPER),$432
 	NO_LOCAL_POINTERS
+	ADD	$LOCAL_REGARGS, SP, X25 // spillArgs using X25
+	CALL	runtime·spillArgs(SB)
+	MOV	CTXT, 32(SP) // save CTXT
+	MOV	CTXT, 8(SP)
+	MOV	X25, 16(SP)
+	CALL	·moveMakeFuncArgPtrs(SB)
+	MOV	32(SP), CTXT // restore CTXT
 	MOV	CTXT, 8(SP)
 	MOV	$argframe+0(FP), T0
 	MOV	T0, 16(SP)
-	ADD	$40, SP, T1
+	MOV	ZERO, LOCAL_RETVALID(SP)
+	ADD	$LOCAL_RETVALID, SP, T1
 	MOV	T1, 24(SP)
-	MOV	ZERO, 32(SP)
-	MOVB	ZERO, 40(SP)
+	ADD	$LOCAL_REGARGS, SP, T1
+	MOV	T1, 32(SP) // frame size to 32+SP as callreflect args
 	CALL	·callMethod(SB)
+	ADD	$LOCAL_REGARGS, SP, X25 // unspillArgs using X25
+	CALL	runtime·unspillArgs(SB)
 	RET
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index edc37d4878..54a02173c3 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -1332,7 +1332,8 @@ func getStackMap(frame *stkframe, cache *pcvalueCache, debug bool) (locals, args
 	}
 
 	// stack objects.
-	if (GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "ppc64" || GOARCH == "ppc64le") && unsafe.Sizeof(abi.RegArgs{}) > 0 && frame.argmap != nil {
+	if (GOARCH == "amd64" || GOARCH == "arm64" || GOARCH == "ppc64" || GOARCH == "ppc64le" || GOARCH == "riscv64") &&
+		unsafe.Sizeof(abi.RegArgs{}) > 0 && frame.argmap != nil {
 		// argmap is set when the function is reflect.makeFuncStub or reflect.methodValueCall.
 		// We don't actually use argmap in this case, but we need to fake the stack object
 		// record for these frames which contain an internal/abi.RegArgs at a hard-coded offset.