pass,printer: display required ISA features (#120)

Fixes #119

pass/isa.go

@@ -0,0 +1,31 @@
+package pass
+
+import (
+	"sort"
+
+	"github.com/mmcloughlin/avo/ir"
+)
+
+// RequiredISAExtensions determines ISA extensions required for the given
+// function. Populates the ISA field.
+func RequiredISAExtensions(fn *ir.Function) error {
+	// Collect ISA set.
+	set := map[string]bool{}
+	for _, i := range fn.Instructions() {
+		for _, isa := range i.ISA {
+			set[isa] = true
+		}
+	}
+
+	if len(set) == 0 {
+		return nil
+	}
+
+	// Populate the function's ISA field with the unique sorted list.
+	for isa := range set {
+		fn.ISA = append(fn.ISA, isa)
+	}
+	sort.Strings(fn.ISA)
+
+	return nil
+}

pass/isa_test.go

@@ -0,0 +1,25 @@
+package pass
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/mmcloughlin/avo/ir"
+)
+
+func TestRequiredISAExtensions(t *testing.T) {
+	f := ir.NewFunction("ISAs")
+	f.AddInstruction(&ir.Instruction{ISA: nil})
+	f.AddInstruction(&ir.Instruction{ISA: []string{"B", "A"}})
+	f.AddInstruction(&ir.Instruction{ISA: []string{"A", "C"}})
+
+	err := RequiredISAExtensions(f)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expect := []string{"A", "B", "C"}
+	if !reflect.DeepEqual(f.ISA, expect) {
+		t.FailNow()
+	}
+}

pass/pass.go

@@ -21,6 +21,7 @@ var Compile = Concat(
 	FunctionPass(VerifyAllocation),
 	Func(IncludeTextFlagHeader),
 	FunctionPass(PruneSelfMoves),
+	FunctionPass(RequiredISAExtensions),
 )
 
 // Interface for a processing pass.