feat(asm): emit the riscv64 local-exec TLS sequence

Assisted-by: GLM 5.3

asm/link.go

@@ -98,6 +98,7 @@ const (
 	RelRISCVPCRELIType                  // R_RISCV_PCREL_ITYPE (AUIPC + I-type pair)
 	RelRISCVPCRELSType                  // R_RISCV_PCREL_STYPE (AUIPC + S-type pair)
 	RelRISCVJal                         // R_RISCV_JAL (J-type call)
+	RelRISCVTLSLE                       // R_RISCV_TLS_LE (LUI + I-type local-exec pair)
 	RelLoong64AddrHi                    // R_LOONG64_ADDR_HI (pcalau12i)
 	RelLoong64AddrLo                    // R_LOONG64_ADDR_LO (addi.d/ld/st)
 	RelArm64Addr                        // R_ADDRARM64 (ADRP + ADD pair)
@@ -335,6 +336,35 @@ func AssembleFile(f *ast.File, opts ...AssembleOption) (*Image, error) {
 	return img, nil
 }
 
+// riscvTLSSymbols names the symbols the file declares with the TLSBSS flag
+// (or its legacy numeric constant 256 from textflag.h): the assembler gives
+// their SB references the local-exec TLS sequence.
+func riscvTLSSymbols(f *ast.File) map[string]bool {
+	var tls map[string]bool
+	for _, d := range f.Decls {
+		gd, ok := d.(*ast.Globl)
+		if !ok || gd.Name == nil || gd.Name.Pseudo != "SB" {
+			continue
+		}
+		for _, fl := range gd.Flags {
+			isTLS := fl == "TLSBSS"
+			if !isTLS {
+				if n, err := strconv.Atoi(fl); err == nil && n&256 != 0 {
+					isTLS = true
+				}
+			}
+			if isTLS {
+				if tls == nil {
+					tls = map[string]bool{}
+				}
+				tls[gd.Name.Name] = true
+				break
+			}
+		}
+	}
+	return tls
+}
+
 // AssembleFileRISCV assembles every TEXT function of a parsed RISC-V file
 // and lays out its static symbols (GLOBL/DATA) in a data section behind the
 // code.  SB references in the code are encoded as AUIPC pairs with zero
@@ -344,6 +374,10 @@ func AssembleFileRISCV(f *ast.File) (*Image, error) {
 	if err != nil {
 		return nil, err
 	}
+	// The symbols the file declares TLSBSS resolve through the local-exec
+	// sequence (LUI + ADDIW + ADD of TP), exactly as the toolchain routes
+	// every SB reference whose symbol carries the STLSBSS type.
+	tlsSyms := riscvTLSSymbols(f)
 	// The pooled $i64 constants the wide MOV immediate loads refer to join
 	// the declared data as read-only symbols, deduplicated across the file
 	// (the toolchain synthesises the same symbols into its rodata).
@@ -355,7 +389,7 @@ func AssembleFileRISCV(f *ast.File) (*Image, error) {
 		if !ok {
 			continue
 		}
-		code, labels, relocs, lines, spadj, lits, err := assembleRISCV(t)
+		code, labels, relocs, lines, spadj, lits, err := assembleRISCV(t, tlsSyms)
 		if err != nil {
 			return nil, fmt.Errorf("%s: %w", t.Name.Name, err)
 		}