riscv: add "target-abi" metadata flag

This flag is necessary in LLVM 15 because it appears that LLVM 15 has
changed the default target ABI from lp64 to lp64d. This results in a
linker failure. Setting the "target-abi" forces the RISC-V backend to
use the intended target ABI.

builder/build.go

@@ -163,6 +163,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 		Triple:          config.Triple(),
 		CPU:             config.CPU(),
 		Features:        config.Features(),
+		ABI:             config.ABI(),
 		GOOS:            config.GOOS(),
 		GOARCH:          config.GOARCH(),
 		CodeModel:       config.CodeModel(),

builder/library.go

@@ -155,6 +155,9 @@ func (l *Library) load(config *compileopts.Config, tmpdir string) (job *compileJ
 			args = append(args, "-mcpu="+cpu)
 		}
 	}
+	if config.ABI() != "" {
+		args = append(args, "-mabi="+config.ABI())
+	}
 	if strings.HasPrefix(target, "arm") || strings.HasPrefix(target, "thumb") {
 		if strings.Split(target, "-")[2] == "linux" {
 			args = append(args, "-fno-unwind-tables", "-fno-asynchronous-unwind-tables")
@@ -170,10 +173,10 @@ func (l *Library) load(config *compileopts.Config, tmpdir string) (job *compileJ
 		args = append(args, "-mdouble=64")
 	}
 	if strings.HasPrefix(target, "riscv32-") {
-		args = append(args, "-march=rv32imac", "-mabi=ilp32", "-fforce-enable-int128")
+		args = append(args, "-march=rv32imac", "-fforce-enable-int128")
 	}
 	if strings.HasPrefix(target, "riscv64-") {
-		args = append(args, "-march=rv64gc", "-mabi=lp64")
+		args = append(args, "-march=rv64gc")
 	}
 	if strings.HasPrefix(target, "xtensa") {
 		// Hack to work around an issue in the Xtensa port:

compileopts/config.go

@@ -47,6 +47,12 @@ func (c *Config) Features() string {
 	return c.Target.Features + "," + c.Options.LLVMFeatures
 }
 
+// ABI returns the -mabi= flag for this target (like -mabi=lp64). A zero-length
+// string is returned if the target doesn't specify an ABI.
+func (c *Config) ABI() string {
+	return c.Target.ABI
+}
+
 // GOOS returns the GOOS of the target. This might not always be the actual OS:
 // for example, bare-metal targets will usually pretend to be linux to get the
 // standard library to compile.
@@ -230,6 +236,9 @@ func (c *Config) LibcPath(name string) (path string, precompiled bool) {
 	if c.CPU() != "" {
 		archname += "-" + c.CPU()
 	}
+	if c.ABI() != "" {
+		archname += "-" + c.ABI()
+	}
 
 	// Try to load a precompiled library.
 	precompiledDir := filepath.Join(goenv.Get("TINYGOROOT"), "pkg", archname, name)
@@ -338,6 +347,10 @@ func (c *Config) CFlags() []string {
 			cflags = append(cflags, "-mcpu="+c.Target.CPU)
 		}
 	}
+	// Set the -mabi flag, if needed.
+	if c.ABI() != "" {
+		cflags = append(cflags, "-mabi="+c.ABI())
+	}
 	return cflags
 }
 

compileopts/target.go

@@ -26,6 +26,7 @@ type TargetSpec struct {
 	Inherits         []string `json:"inherits"`
 	Triple           string   `json:"llvm-target"`
 	CPU              string   `json:"cpu"`
+	ABI              string   `json:"target-abi"` // rougly equivalent to -mabi= flag
 	Features         string   `json:"features"`
 	GOOS             string   `json:"goos"`
 	GOARCH           string   `json:"goarch"`

compiler/compiler.go

@@ -41,6 +41,7 @@ type Config struct {
 	Triple          string
 	CPU             string
 	Features        string
+	ABI             string
 	GOOS            string
 	GOARCH          string
 	CodeModel       string
@@ -321,6 +322,18 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 		c.dibuilder.Destroy()
 	}
 
+	// Add the "target-abi" flag, which is necessary on RISC-V otherwise it will
+	// pick one that doesn't match the -mabi Clang flag.
+	if c.ABI != "" {
+		c.mod.AddNamedMetadataOperand("llvm.module.flags",
+			c.ctx.MDNode([]llvm.Metadata{
+				llvm.ConstInt(c.ctx.Int32Type(), 1, false).ConstantAsMetadata(), // Error on mismatch
+				c.ctx.MDString("target-abi"),
+				c.ctx.MDString(c.ABI),
+			}),
+		)
+	}
+
 	return c.mod, c.diagnostics
 }
 

compiler/compiler_test.go

@@ -73,6 +73,7 @@ func TestCompiler(t *testing.T) {
 			compilerConfig := &Config{
 				Triple:             config.Triple(),
 				Features:           config.Features(),
+				ABI:                config.ABI(),
 				GOOS:               config.GOOS(),
 				GOARCH:             config.GOARCH(),
 				CodeModel:          config.CodeModel(),

targets/riscv32.json

@@ -1,12 +1,12 @@
 {
 	"inherits": ["riscv"],
 	"llvm-target": "riscv32-unknown-none",
+	"target-abi": "ilp32",
 	"build-tags": ["tinygo.riscv32"],
 	"scheduler": "tasks",
 	"default-stack-size": 2048,
 	"cflags": [
-		"-march=rv32imac",
-		"-mabi=ilp32"
+		"-march=rv32imac"
 	],
 	"ldflags": [
 		"-melf32lriscv"

targets/riscv64.json

@@ -1,10 +1,10 @@
 {
 	"inherits": ["riscv"],
 	"llvm-target": "riscv64-unknown-none",
+	"target-abi": "lp64",
 	"build-tags": ["tinygo.riscv64"],
 	"cflags": [
-		"-march=rv64gc",
-		"-mabi=lp64"
+		"-march=rv64gc"
 	],
 	"ldflags": [
 		"-melf64lriscv"