internal/graphicsdriver/directx: call D3DCompile in parallel

D3DCompile can be very slow on some old machines.

See also https://bugs.chromium.org/p/angleproject/issues/detail?id=422

go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/jfreymuth/oggvorbis v1.0.4
 	golang.org/x/image v0.2.0
 	golang.org/x/mobile v0.0.0-20221110043201-43a038452099
+	golang.org/x/sync v0.1.0
 	golang.org/x/sys v0.3.0
 	golang.org/x/tools v0.4.0
 )

go.sum

@@ -44,6 +44,7 @@ golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
+golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

internal/graphicsdriver/directx/pipeline_windows.go

@@ -19,6 +19,8 @@ import (
 	"math"
 	"unsafe"
 
+	"golang.org/x/sync/errgroup"
+
 	"github.com/hajimehoshi/ebiten/v2/internal/graphics"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 )
@@ -377,28 +379,41 @@ func (p *pipelineStates) ensureRootSignature(device *_ID3D12Device) (rootSignatu
 func newShader(source []byte, defs []_D3D_SHADER_MACRO) (vsh, psh *_ID3DBlob, ferr error) {
 	var flag uint32 = uint32(_D3DCOMPILE_OPTIMIZATION_LEVEL3)
 
-	// Create a shader
+	defer func() {
+		if ferr == nil {
+			return
+		}
+		if vsh != nil {
+			vsh.Release()
+		}
+		if psh != nil {
+			psh.Release()
+		}
+	}()
+
+	var wg errgroup.Group
+	wg.Go(func() error {
 		v, err := _D3DCompile(source, "shader", defs, nil, "VSMain", "vs_5_0", flag, 0)
 		if err != nil {
-		return nil, nil, fmt.Errorf("directx: D3DCompile for VSMain failed, original source: %s, %w", string(source), err)
+			return fmt.Errorf("directx: D3DCompile for VSMain failed, original source: %s, %w", string(source), err)
 		}
-	defer func() {
+		vsh = v
-		if ferr != nil {
+		return nil
-			v.Release()
+	})
-		}
+	wg.Go(func() error {
-	}()
-
 		p, err := _D3DCompile(source, "shader", defs, nil, "PSMain", "ps_5_0", flag, 0)
 		if err != nil {
-		return nil, nil, fmt.Errorf("directx: D3DCompile for PSMain failed, original source: %s, %w", string(source), err)
+			return fmt.Errorf("directx: D3DCompile for PSMain failed, original source: %s, %w", string(source), err)
 		}
-	defer func() {
+		psh = p
-		if ferr != nil {
+		return nil
-			p.Release()
+	})
-		}
-	}()
 
-	return v, p, nil
+	if err := wg.Wait(); err != nil {
+		return nil, nil, err
+	}
+
+	return
 }
 
 func (p *pipelineStates) newPipelineState(device *_ID3D12Device, vsh, psh *_ID3DBlob, blend graphicsdriver.Blend, stencilMode stencilMode, screen bool) (state *_ID3D12PipelineState, ferr error) {