cmd/compile: (fixed) spill output parameters passed in registers as autos

Repair of CL 300749.

ALSO:
found evidence that stack maps for bodyless methods are wrong.
gofmt in test/abi
removed never-executed code in types/size.go

Updates #44816.
Updates #40724.

Change-Id: Ifeb5fee60f60e7c7b58ee0457f58a3265d6cf3f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/302071
Trust: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/ssagen/pgen.go b/src/cmd/compile/internal/ssagen/pgen.go
index 8fa5980dabe..0088f10fa88 100644
--- a/src/cmd/compile/internal/ssagen/pgen.go
+++ b/src/cmd/compile/internal/ssagen/pgen.go
@@ -104,7 +104,9 @@ func (s *ssafn) AllocFrame(f *ssa.Func) {
 	// Reassign stack offsets of the locals that are used.
 	lastHasPtr := false
 	for i, n := range fn.Dcl {
-		if n.Op() != ir.ONAME || n.Class != ir.PAUTO {
+		if n.Op() != ir.ONAME || n.Class != ir.PAUTO && !(n.Class == ir.PPARAMOUT && n.IsOutputParamInRegisters()) {
+			// i.e., stack assign if AUTO, or if PARAMOUT in registers (which has no predefined spill locations)
+			// TODO figure out when we don't need to spill output params.
 			continue
 		}
 		if !n.Used() {
@@ -148,9 +150,9 @@ const maxStackSize = 1 << 30
 func Compile(fn *ir.Func, worker int) {
 	f := buildssa(fn, worker)
 	// Note: check arg size to fix issue 25507.
-	if f.Frontend().(*ssafn).stksize >= maxStackSize || fn.Type().ArgWidth() >= maxStackSize {
+	if f.Frontend().(*ssafn).stksize >= maxStackSize || f.OwnAux.ArgWidth() >= maxStackSize {
 		largeStackFramesMu.Lock()
-		largeStackFrames = append(largeStackFrames, largeStack{locals: f.Frontend().(*ssafn).stksize, args: fn.Type().ArgWidth(), pos: fn.Pos()})
+		largeStackFrames = append(largeStackFrames, largeStack{locals: f.Frontend().(*ssafn).stksize, args: f.OwnAux.ArgWidth(), pos: fn.Pos()})
 		largeStackFramesMu.Unlock()
 		return
 	}
@@ -166,7 +168,7 @@ func Compile(fn *ir.Func, worker int) {
 	if pp.Text.To.Offset >= maxStackSize {
 		largeStackFramesMu.Lock()
 		locals := f.Frontend().(*ssafn).stksize
-		largeStackFrames = append(largeStackFrames, largeStack{locals: locals, args: fn.Type().ArgWidth(), callee: pp.Text.To.Offset - locals, pos: fn.Pos()})
+		largeStackFrames = append(largeStackFrames, largeStack{locals: locals, args: f.OwnAux.ArgWidth(), callee: pp.Text.To.Offset - locals, pos: fn.Pos()})
 		largeStackFramesMu.Unlock()
 		return
 	}
@@ -189,6 +191,12 @@ func StackOffset(slot ssa.LocalSlot) int32 {
 	n := slot.N
 	var off int64
 	switch n.Class {
+	case ir.PPARAM, ir.PPARAMOUT:
+		if !n.IsOutputParamInRegisters() {
+			off = n.FrameOffset() + base.Ctxt.FixedFrameSize()
+			break
+		}
+		fallthrough // PPARAMOUT in registers allocates like an AUTO
 	case ir.PAUTO:
 		off = n.FrameOffset()
 		if base.Ctxt.FixedFrameSize() == 0 {
@@ -197,8 +205,6 @@ func StackOffset(slot ssa.LocalSlot) int32 {
 		if objabi.Framepointer_enabled {
 			off -= int64(types.PtrSize)
 		}
-	case ir.PPARAM, ir.PPARAMOUT:
-		off = n.FrameOffset() + base.Ctxt.FixedFrameSize()
 	}
 	return int32(off + slot.Off)
 }