cmd/internal/obj/riscv: mark stack bounds check prologue nonpreemptible

This is similar to CL 207350, for RISCV64.

May fix #50263.
Updates #35470.

Change-Id: I0d39e195e8254d65fa1aca1cdf1fc553aa8b7cba
Reviewed-on: https://go-review.googlesource.com/c/go/+/373434
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/cmd/internal/obj/riscv/obj.go b/src/cmd/internal/obj/riscv/obj.go
index 5755b118db00f2833d5de75a3cc711d9535c05fb..9f16de0c8c44cb866445d0451c1a36692a75c09f 100644 (file)
--- a/src/cmd/internal/obj/riscv/obj.go
+++ b/src/cmd/internal/obj/riscv/obj.go
@@ -790,6 +790,12 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgA
        p.To.Type = obj.TYPE_REG
        p.To.Reg = REG_X10
 
+       // Mark the stack bound check and morestack call async nonpreemptible.
+       // If we get preempted here, when resumed the preemption request is
+       // cleared, but we'll still call morestack, which will double the stack
+       // unnecessarily. See issue #35470.
+       p = ctxt.StartUnsafePoint(p, newprog)
+
        var to_done, to_more *obj.Prog
 
        if framesize <= objabi.StackSmall {
@@ -854,7 +860,7 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgA
                to_done = p
        }
 
-       p = ctxt.EmitEntryLiveness(cursym, p, newprog)
+       p = ctxt.EmitEntryStackMap(cursym, p, newprog)
 
        // CALL runtime.morestack(SB)
        p = obj.Appendp(p, newprog)
@@ -872,6 +878,8 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, cursym *obj.LSym, newprog obj.ProgA
        }
        jalToSym(ctxt, p, REG_X5)
 
+       p = ctxt.EndUnsafePoint(p, newprog, -1)
+
        // JMP start
        p = obj.Appendp(p, newprog)
        p.As = AJAL