[dev.regabi] cmd/compile: always use the compile queue

The compiler currently has two modes for compilation: one where it
compiles each function as it sees them, and another where it enqueues
them all into a work queue. A subsequent CL is going to reorder
function compilation to ensure that functions are always compiled
before any non-trivial function literals they enclose, and this will
be easier if we always use the compile work queue.

Also, fewer compilation modes makes things simpler to reason about.

Change-Id: Ie090e81f7476c49486296f2b90911fa0a466a5dd
Reviewed-on: https://go-review.googlesource.com/c/go/+/283313
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

5 files changed, 27 insertions, 72 deletions

diff --git a/src/cmd/compile/internal/base/debug.go b/src/cmd/compile/internal/base/debug.go
index 3acdcea846..164941bb26 100644
--- a/src/cmd/compile/internal/base/debug.go
+++ b/src/cmd/compile/internal/base/debug.go
@@ -32,7 +32,6 @@ type DebugFlags struct {
 	Append        int    `help:"print information about append compilation"`
 	Checkptr      int    `help:"instrument unsafe pointer conversions"`
 	Closure       int    `help:"print information about closure compilation"`
-	CompileLater  int    `help:"compile functions as late as possible"`
 	DclStack      int    `help:"run internal dclstack check"`
 	Defer         int    `help:"print information about defer compilation"`
 	DisableNil    int    `help:"disable nil checks"`
diff --git a/src/cmd/compile/internal/gc/compile.go b/src/cmd/compile/internal/gc/compile.go
index 25b1c76737..b9c10056b4 100644
--- a/src/cmd/compile/internal/gc/compile.go
+++ b/src/cmd/compile/internal/gc/compile.go
@@ -26,21 +26,17 @@ var (
 	compilequeue []*ir.Func // functions waiting to be compiled
 )
 
-func funccompile(fn *ir.Func) {
+func enqueueFunc(fn *ir.Func) {
 	if ir.CurFunc != nil {
-		base.Fatalf("funccompile %v inside %v", fn.Sym(), ir.CurFunc.Sym())
+		base.FatalfAt(fn.Pos(), "enqueueFunc %v inside %v", fn, ir.CurFunc)
 	}
 
-	if fn.Type() == nil {
-		if base.Errors() == 0 {
-			base.Fatalf("funccompile missing type")
-		}
+	if ir.FuncName(fn) == "_" {
+		// Skip compiling blank functions.
+		// Frontend already reported any spec-mandated errors (#29870).
 		return
 	}
 
-	// assign parameter offsets
-	types.CalcSize(fn.Type())
-
 	if len(fn.Body) == 0 {
 		// Initialize ABI wrappers if necessary.
 		ssagen.InitLSym(fn, false)
@@ -48,35 +44,31 @@ func funccompile(fn *ir.Func) {
 		return
 	}
 
-	typecheck.DeclContext = ir.PAUTO
-	ir.CurFunc = fn
-	compile(fn)
-	ir.CurFunc = nil
-	typecheck.DeclContext = ir.PEXTERN
+	errorsBefore := base.Errors()
+	prepareFunc(fn)
+	if base.Errors() > errorsBefore {
+		return
+	}
+
+	compilequeue = append(compilequeue, fn)
 }
 
-func compile(fn *ir.Func) {
+// prepareFunc handles any remaining frontend compilation tasks that
+// aren't yet safe to perform concurrently.
+func prepareFunc(fn *ir.Func) {
 	// Set up the function's LSym early to avoid data races with the assemblers.
 	// Do this before walk, as walk needs the LSym to set attributes/relocations
 	// (e.g. in markTypeUsedInInterface).
 	ssagen.InitLSym(fn, true)
 
-	errorsBefore := base.Errors()
-	walk.Walk(fn)
-	if base.Errors() > errorsBefore {
-		return
-	}
-
-	// From this point, there should be no uses of Curfn. Enforce that.
-	ir.CurFunc = nil
+	// Calculate parameter offsets.
+	types.CalcSize(fn.Type())
 
-	if ir.FuncName(fn) == "_" {
-		// We don't need to generate code for this function, just report errors in its body.
-		// At this point we've generated any errors needed.
-		// (Beyond here we generate only non-spec errors, like "stack frame too large".)
-		// See issue 29870.
-		return
-	}
+	typecheck.DeclContext = ir.PAUTO
+	ir.CurFunc = fn
+	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
@@ -95,28 +87,6 @@ func compile(fn *ir.Func) {
 			}
 		}
 	}
-
-	if compilenow(fn) {
-		ssagen.Compile(fn, 0)
-	} else {
-		compilequeue = append(compilequeue, fn)
-	}
-}
-
-// compilenow reports whether to compile immediately.
-// If functions are not compiled immediately,
-// they are enqueued in compilequeue,
-// which is drained by compileFunctions.
-func compilenow(fn *ir.Func) bool {
-	// Issue 38068: if this function is a method AND an inline
-	// candidate AND was not inlined (yet), put it onto the compile
-	// queue instead of compiling it immediately. This is in case we
-	// wind up inlining it into a method wrapper that is generated by
-	// compiling a function later on in the Target.Decls list.
-	if ir.IsMethod(fn) && isInlinableButNotInlined(fn) {
-		return false
-	}
-	return base.Flag.LowerC == 1 && base.Debug.CompileLater == 0
 }
 
 // compileFunctions compiles all functions in compilequeue.
@@ -163,16 +133,3 @@ func compileFunctions() {
 		types.CalcSizeDisabled = false
 	}
 }
-
-// isInlinableButNotInlined returns true if 'fn' was marked as an
-// inline candidate but then never inlined (presumably because we
-// found no call sites).
-func isInlinableButNotInlined(fn *ir.Func) bool {
-	if fn.Inl == nil {
-		return false
-	}
-	if fn.Sym() == nil {
-		return true
-	}
-	return !fn.Linksym().WasInlined()
-}
diff --git a/src/cmd/compile/internal/gc/main.go b/src/cmd/compile/internal/gc/main.go
index 1541bc4285..2903d64ff8 100644
--- a/src/cmd/compile/internal/gc/main.go
+++ b/src/cmd/compile/internal/gc/main.go
@@ -300,9 +300,8 @@ func Main(archInit func(*ssagen.ArchInfo)) {
 	base.Timer.Start("be", "compilefuncs")
 	fcount := int64(0)
 	for i := 0; i < len(typecheck.Target.Decls); i++ {
-		n := typecheck.Target.Decls[i]
-		if n.Op() == ir.ODCLFUNC {
-			funccompile(n.(*ir.Func))
+		if fn, ok := typecheck.Target.Decls[i].(*ir.Func); ok {
+			enqueueFunc(fn)
 			fcount++
 		}
 	}
diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go
index fbb2145e1b..753db80f76 100644
--- a/src/cmd/compile/internal/gc/obj.go
+++ b/src/cmd/compile/internal/gc/obj.go
@@ -131,9 +131,8 @@ func dumpdata() {
 	// It was not until issue 24761 that we found any code that required a loop at all.
 	for {
 		for i := numDecls; i < len(typecheck.Target.Decls); i++ {
-			n := typecheck.Target.Decls[i]
-			if n.Op() == ir.ODCLFUNC {
-				funccompile(n.(*ir.Func))
+			if n, ok := typecheck.Target.Decls[i].(*ir.Func); ok {
+				enqueueFunc(n)
 			}
 		}
 		numDecls = len(typecheck.Target.Decls)
diff --git a/src/cmd/compile/internal/liveness/plive.go b/src/cmd/compile/internal/liveness/plive.go
index 26d90824b2..8d1754c813 100644
--- a/src/cmd/compile/internal/liveness/plive.go
+++ b/src/cmd/compile/internal/liveness/plive.go
@@ -1223,6 +1223,7 @@ func WriteFuncMap(fn *ir.Func) {
 	if ir.FuncName(fn) == "_" || fn.Sym().Linkname != "" {
 		return
 	}
+	types.CalcSize(fn.Type())
 	lsym := base.Ctxt.Lookup(fn.LSym.Name + ".args_stackmap")
 	nptr := int(fn.Type().ArgWidth() / int64(types.PtrSize))
 	bv := bitvec.New(int32(nptr) * 2)