Add riscv64-linux-android support

Add barebones riscv64-linux-android support.  This should be enough
to add riscv64-specific entries to Android.bp files, but can't
actually compile anything until there are riscv64 toolchains.

Test: arch_test.go
Change-Id: I0dcc7e797d9352dd38243be908a7f19004ff3db1
diff --git a/cc/config/riscv64_device.go b/cc/config/riscv64_device.go
new file mode 100644
index 0000000..d8918f1
--- /dev/null
+++ b/cc/config/riscv64_device.go
@@ -0,0 +1,140 @@
+// Copyright 2022 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import (
+	"fmt"
+	"strings"
+
+	"android/soong/android"
+)
+
+var (
+	riscv64Cflags = []string{
+		// Help catch common 32/64-bit errors.
+		"-Werror=implicit-function-declaration",
+	}
+
+	riscv64ArchVariantCflags = map[string][]string{}
+
+	riscv64Ldflags = []string{
+		"-Wl,--hash-style=gnu",
+		"-Wl,-z,separate-code",
+	}
+
+	riscv64Lldflags = append(riscv64Ldflags,
+		"-Wl,-z,max-page-size=4096")
+
+	riscv64Cppflags = []string{}
+
+	riscv64CpuVariantCflags = map[string][]string{}
+)
+
+const ()
+
+func init() {
+
+	exportedVars.ExportStringListStaticVariable("Riscv64Ldflags", riscv64Ldflags)
+	exportedVars.ExportStringListStaticVariable("Riscv64Lldflags", riscv64Lldflags)
+
+	exportedVars.ExportStringListStaticVariable("Riscv64Cflags", riscv64Cflags)
+	exportedVars.ExportStringListStaticVariable("Riscv64Cppflags", riscv64Cppflags)
+
+	exportedVars.ExportVariableReferenceDict("Riscv64ArchVariantCflags", riscv64ArchVariantCflagsVar)
+	exportedVars.ExportVariableReferenceDict("Riscv64CpuVariantCflags", riscv64CpuVariantCflagsVar)
+	exportedVars.ExportVariableReferenceDict("Riscv64CpuVariantLdflags", riscv64CpuVariantLdflags)
+}
+
+var (
+	riscv64ArchVariantCflagsVar = map[string]string{}
+
+	riscv64CpuVariantCflagsVar = map[string]string{}
+
+	riscv64CpuVariantLdflags = map[string]string{}
+)
+
+type toolchainRiscv64 struct {
+	toolchainBionic
+	toolchain64Bit
+
+	ldflags         string
+	lldflags        string
+	toolchainCflags string
+}
+
+func (t *toolchainRiscv64) Name() string {
+	return "riscv64"
+}
+
+func (t *toolchainRiscv64) IncludeFlags() string {
+	return ""
+}
+
+func (t *toolchainRiscv64) ClangTriple() string {
+	return "riscv64-linux-android"
+}
+
+func (t *toolchainRiscv64) Cflags() string {
+	return "${config.Riscv64Cflags}"
+}
+
+func (t *toolchainRiscv64) Cppflags() string {
+	return "${config.Riscv64Cppflags}"
+}
+
+func (t *toolchainRiscv64) Ldflags() string {
+	return t.ldflags
+}
+
+func (t *toolchainRiscv64) Lldflags() string {
+	return t.lldflags
+}
+
+func (t *toolchainRiscv64) ToolchainCflags() string {
+	return t.toolchainCflags
+}
+
+func (toolchainRiscv64) LibclangRuntimeLibraryArch() string {
+	return "riscv64"
+}
+
+func riscv64ToolchainFactory(arch android.Arch) Toolchain {
+	switch arch.ArchVariant {
+	case "":
+	default:
+		panic(fmt.Sprintf("Unknown Riscv64 architecture version: %q", arch.ArchVariant))
+	}
+
+	toolchainCflags := []string{riscv64ArchVariantCflagsVar[arch.ArchVariant]}
+	toolchainCflags = append(toolchainCflags,
+		variantOrDefault(riscv64CpuVariantCflagsVar, arch.CpuVariant))
+
+	extraLdflags := variantOrDefault(riscv64CpuVariantLdflags, arch.CpuVariant)
+	return &toolchainRiscv64{
+		ldflags: strings.Join([]string{
+			"${config.Riscv64Ldflags}",
+			extraLdflags,
+		}, " "),
+		lldflags: strings.Join([]string{
+			"${config.Riscv64Lldflags}",
+			extraLdflags,
+		}, " "),
+		toolchainCflags: strings.Join(toolchainCflags, " "),
+	}
+}
+
+func init() {
+	registerToolchainFactory(android.Android, android.Riscv64, riscv64ToolchainFactory)
+}