[dev.regabi] cmd/compile: move stkobj symbol generation to SSA

The code for allocating linksyms and recording that we need runtime
type descriptors is now concurrent-safe, so move it to where those
symbols are actually needed to reduce complexity and risk of failing
to generate all needed symbols in advance.

For #43701.

Change-Id: I759d2508213ac9a4e0b504b51a75fa10dfa37a8d
Reviewed-on: https://go-review.googlesource.com/c/go/+/284076
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Trust: Matthew Dempsky <mdempsky@google.com>

Author: mdempsky

src/cmd/compile/internal/gc/compile.go

@@ -13,7 +13,6 @@ import (
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/liveness"
-	"cmd/compile/internal/reflectdata"
 	"cmd/compile/internal/ssagen"
 	"cmd/compile/internal/typecheck"
 	"cmd/compile/internal/types"
@@ -84,21 +83,6 @@ func prepareFunc(fn *ir.Func) {
 	walk.Walk(fn)
 	ir.CurFunc = nil // enforce no further uses of CurFunc
 	typecheck.DeclContext = ir.PEXTERN
-
-	// Make sure type syms are declared for all types that might
-	// be types of stack objects. We need to do this here
-	// because symbols must be allocated before the parallel
-	// phase of the compiler.
-	for _, n := range fn.Dcl {
-		if liveness.ShouldTrack(n) && n.Addrtaken() {
-			reflectdata.WriteType(n.Type())
-			// Also make sure we allocate a linker symbol
-			// for the stack object data, for the same reason.
-			if fn.LSym.Func().StackObjects == nil {
-				fn.LSym.Func().StackObjects = base.Ctxt.Lookup(fn.LSym.Name + ".stkobj")
-			}
-		}
-	}
 }
 
 // compileFunctions compiles all functions in compilequeue.

src/cmd/compile/internal/ssagen/ssa.go

@@ -6494,18 +6494,16 @@ func emitStackObjects(e *ssafn, pp *objw.Progs) {
 
 	// Populate the stack object data.
 	// Format must match runtime/stack.go:stackObjectRecord.
-	x := e.curfn.LSym.Func().StackObjects
+	x := base.Ctxt.Lookup(e.curfn.LSym.Name + ".stkobj")
+	e.curfn.LSym.Func().StackObjects = x
 	off := 0
 	off = objw.Uintptr(x, off, uint64(len(vars)))
 	for _, v := range vars {
 		// Note: arguments and return values have non-negative Xoffset,
 		// in which case the offset is relative to argp.
 		// Locals have a negative Xoffset, in which case the offset is relative to varp.
 		off = objw.Uintptr(x, off, uint64(v.FrameOffset()))
-		if !types.TypeSym(v.Type()).Siggen() {
-			e.Fatalf(v.Pos(), "stack object's type symbol not generated for type %s", v.Type())
-		}
-		off = objw.SymPtr(x, off, reflectdata.WriteType(v.Type()), 0)
+		off = objw.SymPtr(x, off, reflectdata.TypeLinksym(v.Type()), 0)
 	}
 
 	// Emit a funcdata pointing at the stack object data.