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ARM64: Use movi to materialize FP constants.

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Thanks to Peter Cawley. #1245
This commit is contained in:
Mike Pall
2024-08-15 00:22:47 +02:00
parent 2d54213e7c
commit 6f834087d0
3 changed files with 35 additions and 0 deletions
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14
src/lj_emit_arm64.h
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@@ -66,6 +66,17 @@ static uint32_t emit_isfpk64(uint64_t n)
return ~0u;
}
static uint32_t emit_isfpmovi(uint64_t n)
{
/* Is every byte either 0x00 or 0xff? */
if ((n & U64x(01010101,01010101)) * 0xff != n) return 0;
/* Form 8-bit value by taking one bit from each byte. */
n &= U64x(80402010,08040201);
n = (n * U64x(01010101,01010101)) >> 56;
/* Split into the format expected by movi. */
return ((n & 0xe0) << 6) | 0x700 | (n & 0x1f);
}
/* -- Emit basic instructions --------------------------------------------- */
static void emit_dnma(ASMState *as, A64Ins ai, Reg rd, Reg rn, Reg rm, Reg ra)
@@ -300,6 +311,9 @@ static void emit_loadk64(ASMState *as, Reg r, IRIns *ir)
if (fpk != ~0u) {
emit_d(as, A64I_FMOV_DI | A64F_FP8(fpk), (r & 31));
return;
} else if ((fpk = emit_isfpmovi(*k))) {
emit_d(as, A64I_MOVI_DI | (fpk << 5), (r & 31));
return;
}
}
ofs = glofs(as, k);