internal/rosa: lazy initialise llvm

This significantly improves performance.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/llvm.go

@@ -5,6 +5,7 @@ import (
 	"slices"
 	"strconv"
 	"strings"
+	"sync"
 
 	"hakurei.app/container/check"
 	"hakurei.app/internal/pkg"
@@ -72,8 +73,8 @@ func llvmFlagName(flag int) string {
 	}
 }
 
-// newLLVM returns a [pkg.Artifact] containing a LLVM variant.
+// newLLVMVariant returns a [pkg.Artifact] containing a LLVM variant.
-func (t Toolchain) newLLVM(variant string, attr *llvmAttr) pkg.Artifact {
+func (t Toolchain) newLLVMVariant(variant string, attr *llvmAttr) pkg.Artifact {
 	const (
 		version  = "21.1.8"
 		checksum = "8SUpqDkcgwOPsqHVtmf9kXfFeVmjVxl4LMn-qSE1AI_Xoeju-9HaoPNGtidyxyka"
@@ -219,8 +220,8 @@ cat /usr/src/llvm-patches/* | patch -p 1
 	})
 }
 
-// NewLLVM returns LLVM toolchain across multiple [pkg.Artifact].
+// newLLVM returns LLVM toolchain across multiple [pkg.Artifact].
-func (t Toolchain) NewLLVM() (musl, compilerRT, runtimes, clang pkg.Artifact) {
+func (t Toolchain) newLLVM() (musl, compilerRT, runtimes, clang pkg.Artifact) {
 	var target string
 	switch runtime.GOARCH {
 	case "386", "amd64":
@@ -236,7 +237,7 @@ func (t Toolchain) NewLLVM() (musl, compilerRT, runtimes, clang pkg.Artifact) {
 		{"LLVM_ENABLE_LIBXML2", "OFF"},
 	}
 
-	compilerRT = t.newLLVM("compiler-rt", &llvmAttr{
+	compilerRT = t.newLLVMVariant("compiler-rt", &llvmAttr{
 		env: stage3ExclConcat(t, []string{},
 			"LDFLAGS="+earlyLDFLAGS(false),
 		),
@@ -291,7 +292,7 @@ ln -s \
 		),
 	})
 
-	runtimes = t.newLLVM("runtimes", &llvmAttr{
+	runtimes = t.newLLVMVariant("runtimes", &llvmAttr{
 		env: stage3ExclConcat(t, []string{},
 			"LDFLAGS="+earlyLDFLAGS(false),
 		),
@@ -310,7 +311,7 @@ ln -s \
 		},
 	})
 
-	clang = t.newLLVM("clang", &llvmAttr{
+	clang = t.newLLVMVariant("clang", &llvmAttr{
 		flags: llvmProjectClang | llvmProjectLld,
 		env: stage3ExclConcat(t, []string{},
 			"CFLAGS="+earlyCFLAGS,
@@ -459,3 +460,18 @@ index 64324a3f8b01..15ce70b68217 100644
 
 	return
 }
+
+var (
+	// llvm stores the result of Toolchain.newLLVM.
+	llvm [_toolchainEnd][4]pkg.Artifact
+	// llvmOnce is for lazy initialisation of llvm.
+	llvmOnce [_toolchainEnd]sync.Once
+)
+
+// NewLLVM returns LLVM toolchain across multiple [pkg.Artifact].
+func (t Toolchain) NewLLVM() (musl, compilerRT, runtimes, clang pkg.Artifact) {
+	llvmOnce[t].Do(func() {
+		llvm[t][0], llvm[t][1], llvm[t][2], llvm[t][3] = t.newLLVM()
+	})
+	return llvm[t][0], llvm[t][1], llvm[t][2], llvm[t][3]
+}

internal/rosa/rosa.go

@@ -114,6 +114,10 @@ const (
 
 	// Std denotes the standard Rosa OS toolchain.
 	Std
+
+	// _toolchainEnd is the total number of toolchains available and does not
+	// denote a valid toolchain.
+	_toolchainEnd
 )
 
 // stage3Concat concatenates s and values. If the current toolchain is