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arm64-asm.c: fix shift instruction encoding to match ARM ISA

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LSL/LSR/ASR immediate shifts are UBFM/SBFM aliases with specific
immr/imms field encodings:
- LSL #shift: immr = (width - shift) & 0x3F, imms = width - 1
- LSR #shift: immr = shift & 0x3F, imms = width - 1
- ASR #shift: immr = shift & 0x3F, imms = width - 1

Fixes:
- immr field now always masked with 0x3F (6 bits), not width-1
- imms field is constant (width-1), not calculated from shift
- ROR uses EXTR format (Rm=shift, Rn=src, Rd=dest), not UBFM format

Based on ARM ARM documentation for UBFM/SBFM/EXTR instructions.
This commit is contained in:
Benjamin Oldenburg 2026-03-20 19:57:25 +07:00
parent 1153e48335
commit a702dcce9e
1 changed files with 15 additions and 13 deletions
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28
arm64-asm.c
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@ -603,42 +603,44 @@ static void gen_shift(int rd, int rn, int rm_or_imm, int shift_type, int is_imm,
if (is_imm) {
/* Shift by immediate */
switch (shift_type) {
case 0: /* LSL */
case 0: /* LSL - UBFM alias: immr = (width - shift) & 0x3F, imms = width - 1 */
if (rm_or_imm < 0 || rm_or_imm >= width) {
tcc_error("shift immediate out of range");
return;
}
instr = is_64bit ? 0xD3400000 : 0x53000000;
instr |= ((width - rm_or_imm) & (width - 1)) << 16;
instr |= (width - 1 - rm_or_imm) << 10;
instr |= ((width - rm_or_imm) & 0x3F) << 16; /* immr */
instr |= (width - 1) << 10; /* imms */
break;
case 1: /* LSR */
case 1: /* LSR - UBFM alias: immr = shift, imms = width - 1 */
if (rm_or_imm < 0 || rm_or_imm >= width) {
tcc_error("shift immediate out of range");
return;
}
instr = is_64bit ? 0xD3400000 : 0x53000000;
instr |= rm_or_imm << 16;
instr |= (width - 1) << 10;
instr |= (rm_or_imm & 0x3F) << 16; /* immr */
instr |= (width - 1) << 10; /* imms */
break;
case 2: /* ASR */
case 2: /* ASR - SBFM alias: immr = shift, imms = width - 1 */
if (rm_or_imm < 0 || rm_or_imm >= width) {
tcc_error("shift immediate out of range");
return;
}
instr = is_64bit ? 0x93400000 : 0x13000000;
instr |= rm_or_imm << 16;
instr |= (width - 1) << 10;
instr |= (rm_or_imm & 0x3F) << 16; /* immr */
instr |= (width - 1) << 10; /* imms */
break;
case 3: /* ROR */
case 3: /* ROR - EXTR alias: Rm = shift, Rn = source, Rd = dest */
if (rm_or_imm < 0 || rm_or_imm >= width) {
tcc_error("shift immediate out of range");
return;
}
instr = is_64bit ? 0x93C00000 : 0x13800000;
instr |= (rn & 0x1F) << 16;
instr |= (rm_or_imm & (width - 1)) << 10;
break;
instr |= (rm_or_imm & 0x1F) << 16; /* Rm = shift amount */
instr |= (rn & 0x1F) << 5; /* Rn = source */
instr |= rd & 0x1F; /* Rd = dest */
emit_instr32(instr);
return;
default:
tcc_error("unknown shift type");
return;