compiler: add "target-cpu" and "target-features" attributes

This matches Clang, and with that, it adds support for inlining between
Go and C because LLVM only allows inlining if the "target-cpu" and
"target-features" string attributes match.

For example, take a look at the following code:

    // int add(int a, int b) {
    //   return a + b;
    // }
    import "C"

    func main() {
        println(C.add(3, 5))
    }

The 'add' function is not inlined into the main function before this
commit, but after it, it can be inlined and trivially be optimized to
`println(8)`.

compiler/compiler.go

@@ -23,7 +23,7 @@ import (
 // Version of the compiler pacakge. Must be incremented each time the compiler
 // package changes in a way that affects the generated LLVM module.
 // This version is independent of the TinyGo version number.
-const Version = 24 // last change: add layout param to runtime.alloc calls
+const Version = 25 // last change: add "target-cpu" and "target-features" attributes
 
 func init() {
 	llvm.InitializeAllTargets()

compiler/symbol.go

@@ -346,6 +346,12 @@ func (c *compilerContext) addStandardDeclaredAttributes(llvmFn llvm.Value) {
 		attr := c.ctx.CreateEnumAttribute(kind, 0)
 		llvmFn.AddFunctionAttr(attr)
 	}
+	if c.CPU != "" {
+		llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("target-cpu", c.CPU))
+	}
+	if c.Features != "" {
+		llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("target-features", c.Features))
+	}
 }
 
 // addStandardDefinedAttributes adds the set of attributes that are added to

transform/interface-lowering_test.go

@@ -3,7 +3,6 @@ package transform_test
 import (
 	"testing"
 
-	"github.com/tinygo-org/tinygo/compileopts"
 	"github.com/tinygo-org/tinygo/transform"
 	"tinygo.org/x/go-llvm"
 )
@@ -11,7 +10,7 @@ import (
 func TestInterfaceLowering(t *testing.T) {
 	t.Parallel()
 	testTransform(t, "testdata/interface", func(mod llvm.Module) {
-		err := transform.LowerInterfaces(mod, &compileopts.Config{Options: &compileopts.Options{Opt: "2"}})
+		err := transform.LowerInterfaces(mod, defaultTestConfig)
 		if err != nil {
 			t.Error(err)
 		}

transform/transform.go

@@ -21,11 +21,18 @@ import (
 // attributes to a function. For example, it adds optsize when requested from
 // the -opt= compiler flag.
 func AddStandardAttributes(fn llvm.Value, config *compileopts.Config) {
+	ctx := fn.Type().Context()
 	_, sizeLevel, _ := config.OptLevels()
 	if sizeLevel >= 1 {
-		fn.AddFunctionAttr(fn.Type().Context().CreateEnumAttribute(llvm.AttributeKindID("optsize"), 0))
+		fn.AddFunctionAttr(ctx.CreateEnumAttribute(llvm.AttributeKindID("optsize"), 0))
 	}
 	if sizeLevel >= 2 {
-		fn.AddFunctionAttr(fn.Type().Context().CreateEnumAttribute(llvm.AttributeKindID("minsize"), 0))
+		fn.AddFunctionAttr(ctx.CreateEnumAttribute(llvm.AttributeKindID("minsize"), 0))
+	}
+	if config.CPU() != "" {
+		fn.AddFunctionAttr(ctx.CreateStringAttribute("target-cpu", config.CPU()))
+	}
+	if config.Features() != "" {
+		fn.AddFunctionAttr(ctx.CreateStringAttribute("target-features", config.Features()))
 	}
 }

transform/transform_test.go

@@ -21,6 +21,11 @@ import (
 
 var update = flag.Bool("update", false, "update transform package tests")
 
+var defaultTestConfig = &compileopts.Config{
+	Target:  &compileopts.TargetSpec{},
+	Options: &compileopts.Options{Opt: "2"},
+}
+
 // testTransform runs a transformation pass on an input file (pathPrefix+".ll")
 // and checks whether it matches the expected output (pathPrefix+".out.ll"). The
 // output is compared with a fuzzy match that ignores some irrelevant lines such

transform/wasm-abi_test.go

@@ -3,7 +3,6 @@ package transform_test
 import (
 	"testing"
 
-	"github.com/tinygo-org/tinygo/compileopts"
 	"github.com/tinygo-org/tinygo/transform"
 	"tinygo.org/x/go-llvm"
 )
@@ -12,7 +11,7 @@ func TestWasmABI(t *testing.T) {
 	t.Parallel()
 	testTransform(t, "testdata/wasm-abi", func(mod llvm.Module) {
 		// Run ABI change pass.
-		err := transform.ExternalInt64AsPtr(mod, &compileopts.Config{Options: &compileopts.Options{Opt: "2"}})
+		err := transform.ExternalInt64AsPtr(mod, defaultTestConfig)
 		if err != nil {
 			t.Errorf("failed to change wasm ABI: %v", err)
 		}