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

package asm

import (
	"strings"
	"testing"
)

// TestRISCVBigMemOffset_Differential proves the memory-offset expansion
// against the oracle: a load or store whose offset leaves the signed 12-bit
// span materialises the high part in the assembler's temporary register
// (C.LUI, or LUI beyond its six-bit immediate) followed by C.ADD of the base,
// and accesses through it, exactly as the toolchain's instructionsForLoad and
// instructionsForStore synthesise.  The battery spans both sides of the
// 12-bit edge, both int32 boundaries, the compressed and uncompressed LUI
// halves, every width family and the MOV spellings, under a prologue too so
// the size accounting keeps the layout honest.
func TestRISCVBigMemOffset_Differential(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·bigmem(SB), NOSPLIT, $16
	LD 2047(X6), X5			// single word: the edge that still fits
	LD 2048(X6), X5			// hi 1, lo -2048
	LD 4096(X6), X5			// hi 1, lo 0
	SD X5, 8192(X6)			// store side of the same split
	FLD 4096(X6), F5		// FP widths share the expansion
	FSD F5, 8192(X6)
	MOVB 4097(X6), X8		// the MOV widths route through the same load
	MOVHU 4098(X6), X9
	MOV X7, 16384(X6)		// and the same store
	LD 1048576(X6), X10		// hi 256: LUI, not C.LUI
	LD -4097(X6), X11		// hi -1, lo -1
	SD X11, -8192(X6)
	LD 2147483647(X6), X12	// int32 upper boundary
	LD -2147483648(X6), X13	// int32 lower boundary
	RET
`
	path := writeRISCVSrc(t, "bigmem_riscv64.s", src)
	assertRISCVDifferential(t, path, src, "bigmem")
}

// TestRISCVBigMemOffsetFrame_Differential proves the expansion under the
// stack-split guard: a function that opens a frame and calls out gets the
// guard, the prologue and the epilogue ahead of the body, so every body
// offset now depends on the expansion's size accounting having kept the
// layout in step with the emitted bytes.
func TestRISCVBigMemOffsetFrame_Differential(t *testing.T) {
	src := `#include "textflag.h"

TEXT ·bigframe(SB), $16
	CALL extcal(SB)
	LD 4096(X6), X5
	SD X5, 4096(X6)
	FLD 8192(X6), F5
	FSD F5, 8192(X6)
	RET
`
	path := writeRISCVSrc(t, "bigframe_riscv64.s", src)
	assertRISCVDifferential(t, path, src, "bigframe")
}

// TestRISCVBigMemOffsetRejections pins the honest rejections the expansion
// cannot carry: a constant beyond the signed 32-bit span is the toolchain's
// "constant too large" (its Split32BitImmediate has no wider split), and a
// JALR displacement beyond the signed 12-bit span is its I-type range check,
// because the jump would land somewhere else entirely.
func TestRISCVBigMemOffsetRejections(t *testing.T) {
	cases := []struct {
		name string
		src  string
		want string
	}{
		{
			name: "store beyond int32",
			src:  "\tSD X5, 4294967295(X6)\n",
			want: "SD: constant 4294967295 too large",
		},
		{
			name: "load below int32",
			src:  "\tLD -2147483649(X6), X5\n",
			want: "LD: constant -2147483649 too large",
		},
		{
			name: "MOV load beyond int32",
			src:  "\tMOV 4294967296(X6), X5\n",
			want: "MOV: constant 4294967296 too large",
		},
		{
			name: "MOV store beyond int32",
			src:  "\tMOV X5, 4294967296(X6)\n",
			want: "MOV: constant 4294967296 too large",
		},
		{
			name: "FP store beyond int32",
			src:  "\tFSD F5, 4294967296(X6)\n",
			want: "FSD: constant 4294967296 too large",
		},
		{
			name: "FP load beyond int32",
			src:  "\tFLD 4294967296(X6), F5\n",
			want: "FLD: constant 4294967296 too large",
		},
		{
			name: "JALR displacement above 12 bits",
			src:  "\tJALR 4096(X7)\n",
			want: "JALR: signed immediate 4096 must be in range [-2048, 2047] (12 bits)",
		},
		{
			name: "JALR displacement below 12 bits",
			src:  "\tJALR X5, -2049(X7)\n",
			want: "JALR: signed immediate -2049 must be in range [-2048, 2047] (12 bits)",
		},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			fn := firstTextRISCV(t, "#include \"textflag.h\"\n\nTEXT ·r(SB), NOSPLIT, $0\n"+tc.src+"\tRET\n")
			_, _, _, _, _, _, err := assembleRISCV(fn, nil)
			if err == nil {
				t.Fatalf("source assembled, want rejection %q", tc.want)
			}
			if !strings.Contains(err.Error(), tc.want) {
				t.Errorf("error %q does not carry %q", err.Error(), tc.want)
			}
		})
	}
}