[dev.regabi] cmd/compile: added limited //go:registerparams pragma for new ABI dev

This only works for functions; if you try it with a method, it will
fail.  It does work for both local package and imports.  For now,
it tells you when it thinks it sees either a declaration or a call of
such a function (this will normally be silent since no existing
code uses this pragma).

Note: it appears to be really darn hard to figure out if this
pragma was set for a method, and the method's call site.  Better
ir.Node wranglers than I might be able to make headway, but it
seemed unnecessary for this experiment.

Change-Id: I601c2ddd124457bf6d62f714d7ac871705743c0a
Reviewed-on: https://go-review.googlesource.com/c/go/+/279521
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

5 files changed, 27 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/ir/node.go b/src/cmd/compile/internal/ir/node.go
index a2b6e7203b..a1b09b38cc 100644
--- a/src/cmd/compile/internal/ir/node.go
+++ b/src/cmd/compile/internal/ir/node.go
@@ -452,6 +452,9 @@ const (
 
 	// Go command pragmas
 	GoBuildPragma
+
+	RegisterParams // TODO remove after register abi is working
+
 )
 
 func AsNode(n types.Object) Node {
diff --git a/src/cmd/compile/internal/noder/lex.go b/src/cmd/compile/internal/noder/lex.go
index 1095f3344a..cdca9e55f3 100644
--- a/src/cmd/compile/internal/noder/lex.go
+++ b/src/cmd/compile/internal/noder/lex.go
@@ -28,6 +28,7 @@ const (
 		ir.Nosplit |
 		ir.Noinline |
 		ir.NoCheckPtr |
+		ir.RegisterParams | // TODO remove after register abi is working
 		ir.CgoUnsafeArgs |
 		ir.UintptrEscapes |
 		ir.Systemstack |
@@ -79,6 +80,8 @@ func pragmaFlag(verb string) ir.PragmaFlag {
 		// in the argument list.
 		// Used in syscall/dll_windows.go.
 		return ir.UintptrEscapes
+	case "go:registerparams": // TODO remove after register abi is working
+		return ir.RegisterParams
 	case "go:notinheap":
 		return ir.NotInHeap
 	}
diff --git a/src/cmd/compile/internal/ssagen/ssa.go b/src/cmd/compile/internal/ssagen/ssa.go
index 54bde20f1c..3b542cf92a 100644
--- a/src/cmd/compile/internal/ssagen/ssa.go
+++ b/src/cmd/compile/internal/ssagen/ssa.go
@@ -356,6 +356,13 @@ func buildssa(fn *ir.Func, worker int) *ssa.Func {
 	if fn.Pragma&ir.Nosplit != 0 {
 		s.f.NoSplit = true
 	}
+	if fn.Pragma&ir.RegisterParams != 0 { // TODO remove after register abi is working
+		if strings.Contains(name, ".") {
+			base.ErrorfAt(fn.Pos(), "Calls to //go:registerparams method %s won't work, remove the pragma from the declaration.", name)
+		}
+		s.f.Warnl(fn.Pos(), "Declared function %s has register params", name)
+	}
+
 	s.panics = map[funcLine]*ssa.Block{}
 	s.softFloat = s.config.SoftFloat
 
@@ -4685,6 +4692,7 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 	}
 
 	testLateExpansion := false
+	inRegisters := false
 
 	switch n.Op() {
 	case ir.OCALLFUNC:
@@ -4692,6 +4700,13 @@ func (s *state) call(n *ir.CallExpr, k callKind, returnResultAddr bool) *ssa.Val
 		if k == callNormal && fn.Op() == ir.ONAME && fn.(*ir.Name).Class == ir.PFUNC {
 			fn := fn.(*ir.Name)
 			sym = fn.Sym()
+			// TODO remove after register abi is working
+			inRegistersImported := fn.Pragma()&ir.RegisterParams != 0
+			inRegistersSamePackage := fn.Func != nil && fn.Func.Pragma&ir.RegisterParams != 0
+			inRegisters = inRegistersImported || inRegistersSamePackage
+			if inRegisters {
+				s.f.Warnl(n.Pos(), "Called function %s has register params", sym.Linksym().Name)
+			}
 			break
 		}
 		closure = s.expr(fn)
diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index 4d48b80346..1ba8771139 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -976,6 +976,9 @@ func (w *exportWriter) funcExt(n *ir.Name) {
 	w.linkname(n.Sym())
 	w.symIdx(n.Sym())
 
+	// TODO remove after register abi is working.
+	w.uint64(uint64(n.Func.Pragma))
+
 	// Escape analysis.
 	for _, fs := range &types.RecvsParams {
 		for _, f := range fs(n.Type()).FieldSlice() {
diff --git a/src/cmd/compile/internal/typecheck/iimport.go b/src/cmd/compile/internal/typecheck/iimport.go
index c9effabce0..396d09263a 100644
--- a/src/cmd/compile/internal/typecheck/iimport.go
+++ b/src/cmd/compile/internal/typecheck/iimport.go
@@ -647,6 +647,9 @@ func (r *importReader) funcExt(n *ir.Name) {
 	r.linkname(n.Sym())
 	r.symIdx(n.Sym())
 
+	// TODO remove after register abi is working
+	n.SetPragma(ir.PragmaFlag(r.uint64()))
+
 	// Escape analysis.
 	for _, fs := range &types.RecvsParams {
 		for _, f := range fs(n.Type()).FieldSlice() {