// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

package asm

import (
	"bytes"
	"strings"
	"testing"

	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
)

// firstTextRISCV parses assembly source and returns the first TEXT function body.
func firstTextRISCV(t *testing.T, src string) *ast.Text {
	t.Helper()
	f, errs := parser.Parse("f_riscv64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	for _, d := range f.Decls {
		if fn, ok := d.(*ast.Text); ok {
			return fn
		}
	}
	t.Fatal("no TEXT found")
	return nil
}

// assembleRISCVHelper assembles one TEXT function and returns its code bytes.
func assembleRISCVHelper(t *testing.T, fn *ast.Text) []byte {
	t.Helper()
	code, _, _, _, _, err := assembleRISCV(fn)
	if err != nil {
		t.Fatalf("assemble: %v", err)
	}
	return code
}

func TestRISCV_add(t *testing.T) {
	// func add(a, b int64) int64
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·add(SB), NOSPLIT, $0-24
	MOV a+0(FP), X10
	MOV b+8(FP), X11
	ADD X11, X10, X10
	MOV X10, ret+16(FP)
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// should be 12 bytes with RVC: C.LDSP + C.LDSP + ADD + C.SDSP + C.JR
	_ = code
	if len(code) == 0 {
		t.Error("empty output")
	}
}

func TestRISCV_arithmetic(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·arith(SB), NOSPLIT, $0
	ADD X10, X11, X12
	SUB X12, X13, X14
	MUL X14, X15, X16
	DIV X16, X17, X18
	REM X18, X19, X20
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 5 R-type instructions + RET = 5*4 + 4 = 24
	if len(code) != 24 {
		t.Errorf("expected 24 bytes, got %d", len(code))
	}
}

func TestRISCV_loadStore(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·mem(SB), NOSPLIT, $0
	LD (X10), X11
	SD X11, (X12)
	LW (X13), X14
	SW X14, (X15)
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// Four register-relative loads/stores compress (2B each) + JALR (4B) = 12.
	if len(code) != 12 {
		t.Errorf("expected 12 bytes, got %d", len(code))
	}
}

func TestRISCV_immediate(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·imm(SB), NOSPLIT, $0
	ADDI $42, X10, X11
	ANDI $0xFF, X11, X12
	ORI $1, X12, X13
	XORI $0, X13, X14
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 4 I-type + JALR = 4*4 + 4 = 20
	if len(code) != 20 {
		t.Errorf("expected 20 bytes, got %d", len(code))
	}
}

func TestRISCV_branches(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·br(SB), NOSPLIT, $0
	ADDI $1, X10, X10
loop:
	BEQ X10, X11, done
	ADDI $1, X10, X10
	JMP loop
done:
	RET
`)
	code := assembleRISCVHelper(t, fn)
	_ = code
	if len(code) == 0 {
		t.Error("empty output")
	}
}

func TestRISCV_MOV_imm_small(t *testing.T) {
	// MOV $42, rd → ADDI (fits in 12 bits, but not C.LI's 6-bit immediate).
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·small(SB), NOSPLIT, $0
	MOV $42, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// ADDI (4B) + JALR (4B) = 8
	if len(code) != 8 {
		t.Errorf("expected 8 bytes, got %d", len(code))
	}
}

func TestRISCV_MOV_imm_large(t *testing.T) {
	// MOV $0x12345, rd → C.LUI $18 (2B) + ADDIW $837 (4B).
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·large(SB), NOSPLIT, $0
	MOV $0x12345, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.LUI (2B) + ADDIW (4B) + JALR (4B) = 10
	if len(code) != 10 {
		t.Errorf("expected 10 bytes, got %d", len(code))
	}
}

func TestRISCV_MOV_reg(t *testing.T) {
	// MOV rs, rd → ADDI $0, rs, rd, compresses to C.MV
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·reg(SB), NOSPLIT, $0
	MOV X10, X11
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.MV (2B) + JALR (4B) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes, got %d (% x)", len(code), code)
	}
}

func TestRISCV_MOV_frame(t *testing.T) {
	// MOV name+off(FP), rd → load with frame mapping
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·frame(SB), NOSPLIT, $0-8
	MOV a+0(FP), X10
	MOV X10, ret+0(FP)
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.LDSP (2B) + C.SDSP (2B) + JALR (4B) = 8
	if len(code) != 8 {
		t.Errorf("expected 8 bytes, got %d", len(code))
	}
}

func TestRISCV_RVC_loadStore(t *testing.T) {
	// Verify that loads/stores from SP are compressed.
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·rvcstore(SB), NOSPLIT, $0
	LD 0(SP), X10
	SD X10, 8(SP)
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.LDSP (2B) + C.SDSP (2B) + JALR (4B) = 8
	if len(code) != 8 {
		t.Errorf("expected 8 bytes, got %d (% x)", len(code), code)
	}
}

func TestRISCV_atomics(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·amo(SB), NOSPLIT, $0
	AMOADDD X10, (X11), X12
	LRD (X13), X14
	SCD X15, (X16), X17
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 3 AMO instructions (4B each) + JALR (4B) = 16
	if len(code) != 16 {
		t.Errorf("expected 16 bytes, got %d", len(code))
	}
}

func TestRISCV_fpArith(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·fpadd(SB), NOSPLIT, $0
	FADDD F10, F11, F12
	FSUBD F12, F13, F14
	FMULD F14, F15, F16
	FDIVD F16, F17, F18
	FSQRTD F18, F19
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 5 FP instructions (4B each) + JALR (4B) = 24
	if len(code) != 24 {
		t.Errorf("expected 24 bytes, got %d (%d)", len(code), len(code))
	}
}

func TestRISCV_csr(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·csrtest(SB), NOSPLIT, $0
	CSRRS $0x300, X0, X10
	CSRRW $0x305, X10, X11
	CSRRSI $0x304, $5, X12
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 3 CSR instructions (4B each) + JALR (4B) = 16
	if len(code) != 16 {
		t.Errorf("expected 16 bytes, got %d", len(code))
	}
}

func TestRISCV_fma(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·fmatest(SB), NOSPLIT, $0
	FMADDD F10, F11, F12, F13
	FMSUBD F13, F14, F15, F16
	FNMSUBD F16, F17, F18, F19
	FNMADDD F19, F10, F11, F12
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 4 FMA instructions (4B each) + JALR (4B) = 20
	if len(code) != 20 {
		t.Errorf("expected 20 bytes, got %d", len(code))
	}
}

func TestRISCV_conversions(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cvt(SB), NOSPLIT, $0
	FCVTDL X10, F10
	FCVTLD F10, X11
	FMVXD F10, X12
	FMVDX X12, F11
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 4 conversion instructions (4B each) + JALR (4B) = 20
	if len(code) != 20 {
		t.Errorf("expected 20 bytes, got %d", len(code))
	}
}

func TestRISCV_fpCmp(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cmp(SB), NOSPLIT, $0
	FEQD F10, F11, X10
	FLTD F12, F13, X11
	FLED F14, F15, X12
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// 3 FP compare (4B each) + JALR (4B) = 16
	if len(code) != 16 {
		t.Errorf("expected 16 bytes, got %d", len(code))
	}
}

func TestRISCV_forwardBranch(t *testing.T) {
	// Forward label reference; must not fail.
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·fwd(SB), NOSPLIT, $0
	ADDI $1, X10, X10
	BEQ X10, X11, done
	ADDI $1, X10, X10
done:
	RET
`)
	code := assembleRISCVHelper(t, fn)
	_ = code
	if len(code) == 0 {
		t.Error("empty output")
	}
}

func TestRISCV_RVC_ADDI(t *testing.T) {
	// ADDI where rd=rs1 and small imm → C.ADDI
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·caddi(SB), NOSPLIT, $0
	ADDI $5, X10, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.ADDI (2B) + JALR (4B) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes, got %d", len(code))
	}
}

func TestRISCV_RVC_LI(t *testing.T) {
	// ADDI X0, $imm, rd → C.LI
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cli(SB), NOSPLIT, $0
	ADDI $7, X0, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.LI (2B) + JALR (4B) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes, got %d", len(code))
	}
}

func TestRISCV_RVC_LUI(t *testing.T) {
	// LUI rd, small nonzero imm → C.LUI
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·clui(SB), NOSPLIT, $0
	LUI X10, $1
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.LUI (2B) + JALR (4B) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes, got %d", len(code))
	}
}

func TestRISCV_AssembleFile(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·add(SB), NOSPLIT, $0-24
	MOV a+0(FP), X10
	RET

TEXT ·sub(SB), NOSPLIT, $0
	SUB X10, X11, X12
	RET
`
	f, errs := parser.Parse("t_riscv64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	if len(img.Funcs) != 2 {
		t.Fatalf("expected 2 functions, got %d", len(img.Funcs))
	}
	// func add: C.LDSP(2) + JALR(4) = 6
	if img.Funcs[0].Size != 6 {
		t.Errorf("add: expected 6 bytes, got %d", img.Funcs[0].Size)
	}
	// func sub: SUB(4) + JALR(4) = 8
	if img.Funcs[1].Size != 8 {
		t.Errorf("sub: expected 8 bytes, got %d", img.Funcs[1].Size)
	}
}

func TestRISCV_encodings(t *testing.T) {
	// Smoke test that all known RISC-V mnemonics encode successfully.
	tests := []struct {
		name, src string
		wantBytes int
	}{
		{"ADD", "ADD X10, X11, X12\nRET\n", 8},
		{"SUBW", "SUBW X10, X11, X12\nRET\n", 8},
		{"MUL", "MUL X10, X11, X12\nRET\n", 8},
		{"DIVW", "DIVW X10, X11, X12\nRET\n", 8},
		{"REMUW", "REMUW X10, X11, X12\nRET\n", 8},
		{"ADDIW", "ADDIW $5, X10, X11\nRET\n", 8},
		{"SLLI", "SLLI $3, X10, X11\nRET\n", 8}, // ADDI+SLLI? No, SLLI uses I-type
		{"SRLI", "SRLI $2, X10, X11\nRET\n", 8},
		{"SRAI", "SRAI $1, X10, X11\nRET\n", 8},
		{"LB", "LB (X10), X11\nRET\n", 8},
		{"LBU", "LBU (X10), X11\nRET\n", 8},
		{"LH", "LH (X10), X11\nRET\n", 8},
		{"LHU", "LHU (X10), X11\nRET\n", 8},
		{"LWU", "LWU (X10), X11\nRET\n", 8},
		{"SB", "SB X10, (X11)\nRET\n", 8},
		{"SH", "SH X10, (X11)\nRET\n", 8},
		{"SW", "SW X10, (X11)\nRET\n", 6},
		{"LUI", "LUI X10, $0x12345\nRET\n", 8},
		{"AUIPC", "AUIPC X10, $0\nRET\n", 8},
		{"FLW", "FLW (X10), F10\nRET\n", 8},
		{"FSW", "FSW F10, (X11)\nRET\n", 8},
		{"FADDS", "FADDS F10, F11, F12\nRET\n", 8},
		{"FMINS", "FMINS F10, F11, F12\nRET\n", 8},
		{"FMAXD", "FMAXD F10, F11, F12\nRET\n", 8},
		{"FCVTSD", "FCVTSD F10, F11\nRET\n", 8},
		{"FCVTDS", "FCVTDS F10, F11\nRET\n", 8},
		{"FMVXW", "FMVXW F10, X10\nRET\n", 8},
		{"FMADD_S", "FMADDS F10, F11, F12, F13\nRET\n", 8},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·`+tt.name+`(SB), NOSPLIT, $0
	`+tt.src)
			code := assembleRISCVHelper(t, fn)
			if len(code) != tt.wantBytes {
				t.Errorf("expected %d bytes, got %d", tt.wantBytes, len(code))
			}
		})
	}
}

func TestRISCV_RVC_branch(t *testing.T) {
	// Branches are never RVC-compressed (no C.BEQZ/C.BNEZ), matching go tool asm.
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cbeqz(SB), NOSPLIT, $0
	ADDI $1, X10, X10
	BEQ X10, X0, done
	ADDI $1, X10, X10
done:
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.ADDI(2) + BEQ(4) + C.ADDI(2) + JALR(4) = 12
	if len(code) != 12 {
		t.Errorf("expected 12 bytes with uncompressed BEQ, got %d", len(code))
	}
}

func TestRISCV_RVC_CJ(t *testing.T) {
	// JMP target → JAL X0 (never compressed to C.J), matching go tool asm.
	fn := firstTextRISCV(t, `#include "textflag.h"
	TEXT ·cj(SB), NOSPLIT, $0
		JMP done
	done:
		RET
	`)
	code := assembleRISCVHelper(t, fn)
	// JAL(4) + JALR(4) = 8
	if len(code) != 8 {
		t.Errorf("expected 8 bytes with uncompressed JMP, got %d", len(code))
	}
}

func TestRISCV_RVC_CADD(t *testing.T) {
	// ADD where rd==rs1 and both in prime regs → C.ADD.
	fn := firstTextRISCV(t, `#include "textflag.h"
	TEXT ·cadd(SB), NOSPLIT, $0
		ADD X10, X11, X10
		RET
	`)
	code := assembleRISCVHelper(t, fn)
	// C.ADD(2) + JALR(4) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.ADD, got %d", len(code))
	}
}

func TestRISCV_RVC_CADD_commute(t *testing.T) {
	// ADD where rd==rs2 (commutative swap) → C.ADD.
	fn := firstTextRISCV(t, `#include "textflag.h"
	TEXT ·cadd2(SB), NOSPLIT, $0
		ADD X11, X10, X10
		RET
	`)
	code := assembleRISCVHelper(t, fn)
	// C.ADD(2) + JALR(4) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.ADD (commuted), got %d", len(code))
	}
}

func TestRISCV_RVC_CSUB(t *testing.T) {
	// SUB rs2, rs1, rd → C.SUB when rd == rs1 and both in prime regs.
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·csub(SB), NOSPLIT, $0
	SUB X11, X10, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// SUB X11, X10, X10 → rs2=X11, rs1=X10, rd=X10; rd==rs1 → C.SUB (2B) + JALR (4B) = 6.
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.SUB, got %d (% x)", len(code), code)
	}
}

func TestRISCV_RVC_CXOR(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cxor(SB), NOSPLIT, $0
	XOR X10, X11, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.XOR, got %d", len(code))
	}
}

func TestRISCV_RVC_COR(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cor(SB), NOSPLIT, $0
	OR X10, X11, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.OR, got %d", len(code))
	}
}

func TestRISCV_RVC_CAND(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cand(SB), NOSPLIT, $0
	AND X10, X11, X10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.AND, got %d", len(code))
	}
}

func TestRISCV_RVC_CFLDSP(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cfldsp(SB), NOSPLIT, $0-8
	FLD a+0(FP), F10
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.FLDSP(2) + JALR(4) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.FLDSP, got %d", len(code))
	}
}

func TestRISCV_RVC_CFSDSP(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·cfsdsp(SB), NOSPLIT, $0-8
	FSD F10, ret+0(FP)
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// C.FSDSP(2) + JALR(4) = 6
	if len(code) != 6 {
		t.Errorf("expected 6 bytes with C.FSDSP, got %d", len(code))
	}
}

func TestRISCV_SB_addr(t *testing.T) {
	// MOV $sym<>(SB), rd → AUIPC + ADDI (8 bytes for SB).
	src := `#include "textflag.h"
TEXT ·sbaddr(SB), NOSPLIT, $0
	MOV $answer<>(SB), X10
	RET
GLOBL answer<>(SB), RODATA, $8
DATA answer<>+0(SB)/8, $42
`
	f, errs := parser.Parse("t_riscv64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	// AUIPC(4) + ADDI(4) + JALR(4) = 12
	if img.Funcs[0].Size != 12 {
		t.Errorf("expected 12 bytes, got %d", img.Funcs[0].Size)
	}
}

func TestRISCV_SB_store(t *testing.T) {
	// MOV rd, sym<>(SB) → AUIPC + SD (8 bytes for SB).
	src := `#include "textflag.h"
TEXT ·sbstore(SB), NOSPLIT, $0
	MOV X10, result<>(SB)
	RET
GLOBL result<>(SB), NOPTR, $8
`
	f, errs := parser.Parse("t_riscv64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	// AUIPC X31(4) + SD X10,0(X31)(4) + JALR(4) = 12
	if img.Funcs[0].Size != 12 {
		t.Errorf("expected 12 bytes, got %d", img.Funcs[0].Size)
	}
}

func TestRISCV_ELF(t *testing.T) {
	src := `#include "textflag.h"
TEXT ·simple(SB), NOSPLIT, $0
	RET
`
	f, errs := parser.Parse("t_riscv64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	obj, err := img.ELFRISCVObject()
	if err != nil {
		t.Fatalf("ELFRISCVObject: %v", err)
	}
	if len(obj) < 4 || obj[0] != 0x7f || obj[1] != 'E' || obj[2] != 'L' || obj[3] != 'F' {
		t.Fatal("not a valid ELF file")
	}
	if len(obj) >= 20 {
		machine := uint16(obj[18]) | uint16(obj[19])<<8
		if machine != 243 {
			t.Errorf("e_machine = %d, want 243 (EM_RISCV)", machine)
		}
	}
}

func TestRISCV_ELF_withData(t *testing.T) {
	src := `#include "textflag.h"
TEXT ·get(SB), NOSPLIT, $0
	RET
GLOBL val<>(SB), RODATA, $4
DATA val<>+0(SB)/4, $7
`
	f, errs := parser.Parse("t_riscv64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	if len(img.DataSyms) != 1 {
		t.Fatalf("expected 1 data symbol, got %d", len(img.DataSyms))
	}
	if img.DataSyms[0].Name != "val" {
		t.Errorf("data symbol name = %q, want val", img.DataSyms[0].Name)
	}
	if img.DataSyms[0].Size != 4 {
		t.Errorf("data symbol size = %d, want 4", img.DataSyms[0].Size)
	}
	obj, err := img.ELFRISCVObject()
	if err != nil {
		t.Fatalf("ELFRISCVObject: %v", err)
	}
	_ = obj
}

func TestRISCV_SB_load(t *testing.T) {
	// MOV sym<>(SB), rd → AUIPC + LD (8 bytes for SB).
	src := `#include "textflag.h"
TEXT ·sbload(SB), NOSPLIT, $0
	MOV answer<>(SB), X10
	RET
GLOBL answer<>(SB), RODATA, $8
DATA answer<>+0(SB)/8, $42
`
	f, errs := parser.Parse("t_riscv64.s", src)
	if len(errs) > 0 {
		t.Fatalf("parse: %v", errs)
	}
	img, err := AssembleFileRISCV(f)
	if err != nil {
		t.Fatalf("AssembleFileRISCV: %v", err)
	}
	// AUIPC(4) + LD(4) + JALR(4) = 12
	if img.Funcs[0].Size != 12 {
		t.Errorf("expected 12 bytes, got %d", img.Funcs[0].Size)
	}
}

// TestRISCV_RVC_StorePatterns pins the register-relative compressed store
// encodings for offsets with immediate bits 4 and 5 set, byte-identical to
// the toolchain's encodeCS (patterns {5,4,3,7,6} and {5,4,3,2,6}).
// Regression: the store-side patterns dropped imm[4], so every such store
// silently encoded the wrong address while the loads stayed correct.
func TestRISCV_RVC_StorePatterns(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·csstores(SB), NOSPLIT, $0
	SD  X9, 24(X8)
	SW  X10, 16(X11)
	FSD F8, 40(X12)
	LD  24(X8), X9
	LW  16(X11), X10
	FLD 40(X12), F8
	RET
`)
	code := assembleRISCVHelper(t, fn)
	want := []byte{
		0x04, 0xec, // c.sd x9, 24(x8)
		0x88, 0xc9, // c.sw x10, 16(x11)
		0x00, 0xb6, // c.fsd f8, 40(x12)
		0x04, 0x6c, // c.ld x9, 24(x8)
		0x88, 0x49, // c.lw x10, 16(x11)
		0x00, 0x36, // c.fld f8, 40(x12)
		0x67, 0x80, 0x00, 0x00, // jalr x0, 0(x1)
	}
	if !bytes.Equal(code, want) {
		t.Errorf("code = % x\nwant % x", code, want)
	}
}

// TestRISCV_FENCE pins the FENCE encoding: the toolchain expands the bare
// mnemonic to fence iorw, iorw (0x0FF0000F), not fence 0,0.
func TestRISCV_FENCE(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·fence(SB), NOSPLIT, $0
	FENCE
	RET
`)
	code := assembleRISCVHelper(t, fn)
	want := []byte{
		0x0f, 0x00, 0xf0, 0x0f, // fence iorw, iorw
		0x67, 0x80, 0x00, 0x00, // jalr x0, 0(x1)
	}
	if !bytes.Equal(code, want) {
		t.Errorf("code = % x\nwant % x", code, want)
	}
}

// TestRISCV_RVC_WidthSpellings pins the compression of the GOROOT width
// spellings: MOVW and MOVD lower to their base load/store and compress
// exactly like LW/SW/FLD/FSD would (the toolchain compresses these shapes;
// before the normalisation they stayed 4 bytes).
func TestRISCV_RVC_WidthSpellings(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·widths(SB), NOSPLIT, $0-16
	MOVW w+0(FP), X9
	MOVW X9, v+4(FP)
	MOVD d+0(FP), F8
	MOVD F8, r+8(FP)
	RET
`)
	code := assembleRISCVHelper(t, fn)
	want := []byte{
		0xa2, 0x44, // c.lwsp x9, 8
		0x26, 0xc6, // c.swsp x9, 12
		0x22, 0x24, // c.fldsp f8, 8
		0x22, 0xa8, // c.fsdsp f8, 16
		0x67, 0x80, 0x00, 0x00, // jalr x0, 0(x1)
	}
	if !bytes.Equal(code, want) {
		t.Errorf("code = % x\nwant % x", code, want)
	}
}

func TestRISCV_system_instrs(t *testing.T) {
	// Test FENCE, ECALL, EBREAK encoding.
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·sys(SB), NOSPLIT, $0
	FENCE
	ECALL
	EBREAK
	RET
`)
	code := assembleRISCVHelper(t, fn)
	// FENCE(4) + ECALL(4) + C.EBREAK(2) + JALR(4) = 14
	if len(code) != 14 {
		t.Errorf("expected 14 bytes, got %d (% x)", len(code), code)
	}
}

func TestRISCV_MOV_sym_FP_error(t *testing.T) {
	// MOV $sym(FP), rd should return an error (unsupported).
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·badfp(SB), NOSPLIT, $0
	MOV $arg(FP), X10
	RET
`)
	_, _, _, _, _, err := assembleRISCV(fn)
	if err == nil {
		t.Error("expected error for MOV $arg(FP), got nil")
	}
}

func TestRISCV_CALL(t *testing.T) {
	// CALL sym(SB) → JAL X1, sym(SB) with a single R_RISCV_JAL relocation.
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·calltest(SB), NOSPLIT, $0
	CALL ext(SB)
	RET
`)
	code, _, relocs, _, _, err := assembleRISCV(fn)
	if err != nil {
		t.Fatalf("assemble: %v", err)
	}
	// prologue (8) + JAL (4) + epilogue+JALR (8) = 20
	if len(code) != 20 {
		t.Fatalf("expected 20 bytes with CALL sym(SB), got %d", len(code))
	}
	if len(relocs) != 1 {
		t.Fatalf("relocs = %d, want 1", len(relocs))
	}
	r := relocs[0]
	if r.Kind != RelRISCVJal || r.Name != "ext" || r.Off != 8 || r.After != 12 || r.Addend != 0 {
		t.Errorf("reloc = {kind %v off %d after %d name %q addend %d}", r.Kind, r.Off, r.After, r.Name, r.Addend)
	}
	// The JAL instruction itself is JAL X1, 0 at function offset 8.
	wantJAL := wordLE(riscvJType(1, 0))
	if !bytes.Equal(code[8:12], wantJAL) {
		t.Errorf("JAL = % x, want % x", code[8:12], wantJAL)
	}
}

func TestRISCV_CALL_local_error(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·calllocal(SB), NOSPLIT, $0
	CALL sub
sub:
	RET
`)
	_, _, _, _, _, err := assembleRISCV(fn)
	if err == nil {
		t.Error("expected error for CALL to local label, got nil")
	}
}

// TestRISCVIndirectBranch pins the indirect branch encodings: JMP (X5) is the
// toolchain's JALR X0, 0(X5), and the trampoline form JALR rd, offset(rs1)
// takes its destination from the first operand (regression: the base
// register was once read as the destination, silently jumping to X0).
func TestRISCVIndirectBranch(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·f(SB), NOSPLIT, $0-0
	JMP (X5)
	JALR X0, 0(X6)
	JALR X28, 0(X9)
	RET
`)
	code := assembleRISCVHelper(t, fn)
	wantWords(t, code,
		0x00028067, // jalr x0, 5(x0), 0
		0x00030067, // jalr x0, 6(x0), 0
		0x00048e67, // jalr x28, 9(x0), 0
		0x00008067, // jalr x0, 1(x0), 0 (RET)
	)
}

// encodeOneInstrRISCV encodes a single parsed instruction against a synthetic
// offsets map, the smallest honest harness for the branch-range diagnostics:
// the spans are far larger than any source a test would want to spell out.
func encodeOneInstrRISCV(t *testing.T, src string, pc int, offsets map[string]int) ([]byte, error) {
	t.Helper()
	fn := firstTextRISCV(t, "#include \"textflag.h\"\n"+src)
	instr := fn.Body[0].(*ast.Instr)
	return encodeRISCVInstr(instr, pc, offsets, riscvFrameInfo{}, nil)
}

// TestRISCVBranchJumpRange checks that displacements beyond the B-type span
// [-4096, 4094] and the J-type span [-1048576, 1048574] are diagnosed instead
// of wrapping silently to a wrong target.
func TestRISCVBranchJumpRange(t *testing.T) {
	cases := []struct {
		name string
		src  string
		off  int // the target's function-relative offset (pc 0)
		ok   bool
	}{
		{"branch max", "BEQ X10, X11, tgt\nRET\n", 4094, true},
		{"branch past max", "BEQ X10, X11, tgt\nRET\n", 4096, false},
		{"branch back max", "BEQ X10, X11, tgt\nRET\n", -4096, true},
		{"branch back past max", "BEQ X10, X11, tgt\nRET\n", -4098, false},
		{"branchz past max", "BEQZ X10, tgt\nRET\n", 4096, false},
		{"jump max", "JMP tgt\nRET\n", 1048574, true},
		{"jump past max", "JMP tgt\nRET\n", 1048576, false},
		{"jump back max", "JMP tgt\nRET\n", -1048576, true},
		{"jump back past max", "JMP tgt\nRET\n", -1048578, false},
		{"jal past max", "JAL tgt\nRET\n", 1048576, false},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			_, err := encodeOneInstrRISCV(t, "TEXT ·f(SB), NOSPLIT, $0\n\t"+c.src, 0, map[string]int{"tgt": c.off})
			if c.ok && err != nil {
				t.Fatalf("unexpected error: %v", err)
			}
			if !c.ok && err == nil {
				t.Fatal("expected an out-of-range diagnostic, got none")
			}
		})
	}
}

// TestRISCVBranchFarBody drives the range check through the full two-pass
// assembler: a forward branch over a body larger than the B-type span must
// error rather than wrap.
func TestRISCVBranchFarBody(t *testing.T) {
	var sb strings.Builder
	sb.WriteString("#include \"textflag.h\"\nTEXT ·far(SB), NOSPLIT, $0\n\tBEQ X10, X11, done\n")
	for range 1100 {
		sb.WriteString("\tADD X10, X11, X12\n")
	}
	sb.WriteString("done:\n\tRET\n")
	fn := firstTextRISCV(t, sb.String())
	if _, _, _, _, _, err := assembleRISCV(fn); err == nil {
		t.Error("expected a branch-out-of-range error, got none")
	}
}

// TestRISCV_CSRRange checks the CSR address range: the 12-bit field is
// diagnosed rather than masked, so CSRRW $4096 does not silently address
// CSR 0.
func TestRISCV_CSRRange(t *testing.T) {
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·csrhi(SB), NOSPLIT, $0
	CSRRW $4096, X10, X11
	RET
`)
	if _, _, _, _, _, err := assembleRISCV(fn); err == nil {
		t.Error("expected an out-of-range error for CSR $4096, got none")
	}
	fn = firstTextRISCV(t, `#include "textflag.h"
TEXT ·csrmax(SB), NOSPLIT, $0
	CSRRW $4095, X10, X11
	RET
`)
	if _, _, _, _, _, err := assembleRISCV(fn); err != nil {
		t.Errorf("CSR $4095 must assemble: %v", err)
	}
}

// TestRISCV_Imm64Rejected checks that immediates outside the signed 32-bit
// span are diagnosed instead of silently truncated to their low 32 bits (the
// toolchain materialises such constants via SLLI expansion, which this
// assembler does not implement).
func TestRISCV_Imm64Rejected(t *testing.T) {
	cases := []string{
		"MOV $0x123456789, X10",
		"ADDI $0x100000000, X10, X11",
		"ANDI $-0x800000001, X10, X11",
		"SUB $0x100000000, X10, X11",
	}
	for _, src := range cases {
		fn := firstTextRISCV(t, "#include \"textflag.h\"\nTEXT ·wide(SB), NOSPLIT, $0\n\t"+src+"\n\tRET\n")
		if _, _, _, _, _, err := assembleRISCV(fn); err == nil {
			t.Errorf("%s: expected an out-of-range error, got none", src)
		}
	}
	// The full signed 32-bit span still assembles, including the SUB form
	// whose negated immediate only just fits.
	fn := firstTextRISCV(t, `#include "textflag.h"
TEXT ·edge(SB), NOSPLIT, $0
	MOV  $2147483647, X10
	MOV  $-2147483648, X11
	SUB  $0x80000000, X12, X13
	RET
`)
	if _, _, _, _, _, err := assembleRISCV(fn); err != nil {
		t.Errorf("int32-span immediates must assemble: %v", err)
	}
}