pass: add textflags.h if required

Closes #12

ast.go

@@ -99,9 +99,7 @@ type File struct {
 }
 
 func NewFile() *File {
-	return &File{
-		Includes: []string{"textflag.h"},
-	}
+	return &File{}
 }
 
 func (f *File) AddSection(s Section) {

examples/add/add.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out add.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func Add(x uint64, y uint64) uint64
 TEXT ·Add(SB), $0-24
 	MOVQ	x(FP), AX

examples/args/args.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out args.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func StringLen(s string) int
 TEXT ·StringLen(SB), $0-24
 	MOVQ	s_len+8(FP), AX

examples/complex/complex.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out complex.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func Real(z complex128) float64
 TEXT ·Real(SB), $0-24
 	MOVSD	z_real(FP), X0

examples/dot/dot.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out dot.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func Dot(x []float32, y []float32) float32
 TEXT ·Dot(SB), $0-52
 	MOVQ	x_base(FP), AX

examples/fnv1a/fnv1a.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out fnv1a.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func Hash64(data []byte) uint64
 TEXT ·Hash64(SB), $0-32
 	MOVQ	data_base(FP), CX

examples/sha1/sha1.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out sha1.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func block(h *[5]uint32, m []byte)
 TEXT ·block(SB), $64-32
 	MOVQ	h(FP), AX

examples/stadtx/stadtx.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out stadtx.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func Hash(state *State, key []byte) uint64
 TEXT ·Hash(SB), $0-40
 	MOVQ	state(FP), AX

examples/sum/sum.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out sum.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func Sum(xs []uint64) uint64
 TEXT ·Sum(SB), $0-32
 	MOVQ	xs_base(FP), AX

pass/pass.go

@@ -14,6 +14,7 @@ var Compile = Concat(
 	FunctionPass(AllocateRegisters),
 	FunctionPass(BindRegisters),
 	FunctionPass(VerifyAllocation),
+	Func(IncludeTextFlagHeader),
 )
 
 type Interface interface {

pass/textflag.go

@@ -0,0 +1,41 @@
+package pass
+
+import (
+	"github.com/mmcloughlin/avo"
+)
+
+// IncludeTextFlagHeader includes textflag.h if necessary.
+func IncludeTextFlagHeader(f *avo.File) error {
+	const textflagheader = "textflag.h"
+
+	// Check if we already have it.
+	for _, path := range f.Includes {
+		if path == textflagheader {
+			return nil
+		}
+	}
+
+	// Add it if necessary.
+	if requirestextflags(f) {
+		f.Includes = append(f.Includes, textflagheader)
+	}
+
+	return nil
+}
+
+// requirestextflags returns whether the file uses flags in the textflags.h header.
+func requirestextflags(f *avo.File) bool {
+	for _, s := range f.Sections {
+		var a avo.Attribute
+		switch s := s.(type) {
+		case *avo.Function:
+			a = s.Attributes
+		case *avo.Global:
+			a = s.Attributes
+		}
+		if a.ContainsTextFlags() {
+			return true
+		}
+	}
+	return false
+}

printer/goasm_test.go

@@ -22,8 +22,6 @@ func TestBasic(t *testing.T) {
 	AssertPrintsLines(t, ctx, printer.NewGoAsm, []string{
 		"// Code generated by avo. DO NOT EDIT.",
 		"",
-		"#include \"textflag.h\"",
-		"",
 		"// func add(x uint64, y uint64) uint64",
 		"TEXT ·add(SB), $0-24",
 		"\tMOVQ\tx(FP), AX",
@@ -55,8 +53,6 @@ func TestTextDecl(t *testing.T) {
 	AssertPrintsLines(t, ctx, printer.NewGoAsm, []string{
 		"// Code generated by avo. DO NOT EDIT.",
 		"",
-		"#include \"textflag.h\"",
-		"",
 		"// func noargs()",
 		"TEXT ·noargs(SB), $16", // expect only the frame size
 		"\tRET",

tests/cast/cast.s

@@ -1,7 +1,5 @@
 // Code generated by command: go run asm.go -out cast.s -stubs stub.go. DO NOT EDIT.
 
-#include "textflag.h"
-
 // func Split(x uint64) (q uint64, l uint32, w uint16, b uint8)
 TEXT ·Split(SB), $0-23
 	MOVQ	x(FP), AX