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tcg-aarch64: Use MOVN in tcg_out_movi

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When profitable, initialize the register with MOVN instead of MOVZ,
before setting the remaining lanes with MOVK.

Reviewed-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2013-08-14 19:32:56 -07:00 committed by Richard Henderson
parent 929f8b5550
commit dfeb5fe770
1 changed files with 49 additions and 12 deletions
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61
tcg/aarch64/tcg-target.c
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@ -531,24 +531,61 @@ static void tcg_out_movi(TCGContext *s, TCGType type, TCGReg rd,
tcg_target_long value)
{
AArch64Insn insn;
int i, wantinv, shift;
tcg_target_long svalue = value;
tcg_target_long ivalue = ~value;
tcg_target_long imask;
if (type == TCG_TYPE_I32) {
/* For 32-bit values, discard potential garbage in value. For 64-bit
values within [2**31, 2**32-1], we can create smaller sequences by
interpreting this as a negative 32-bit number, while ensuring that
the high 32 bits are cleared by setting SF=0. */
if (type == TCG_TYPE_I32 || (value & ~0xffffffffull) == 0) {
svalue = (int32_t)value;
value = (uint32_t)value;
ivalue = (uint32_t)ivalue;
type = TCG_TYPE_I32;
}
/* count trailing zeros in 16 bit steps, mapping 64 to 0. Emit the
first MOVZ with the half-word immediate skipping the zeros, with a shift
(LSL) equal to this number. Then all next instructions use MOVKs.
Zero the processed half-word in the value, continue until empty.
We build the final result 16bits at a time with up to 4 instructions,
but do not emit instructions for 16bit zero holes. */
/* Would it take fewer insns to begin with MOVN? For the value and its
inverse, count the number of 16-bit lanes that are 0. */
for (i = wantinv = imask = 0; i < 64; i += 16) {
tcg_target_long mask = 0xffffull << i;
if ((value & mask) == 0) {
wantinv -= 1;
}
if ((ivalue & mask) == 0) {
wantinv += 1;
imask |= mask;
}
}
/* If we had more 0xffff than 0x0000, invert VALUE and use MOVN. */
insn = I3405_MOVZ;
do {
unsigned shift = ctz64(value) & (63 & -16);
tcg_out_insn_3405(s, insn, shift >= 32, rd, value >> shift, shift);
if (wantinv > 0) {
value = ivalue;
insn = I3405_MOVN;
}
/* Find the lowest lane that is not 0x0000. */
shift = ctz64(value) & (63 & -16);
tcg_out_insn_3405(s, insn, type, rd, value >> shift, shift);
if (wantinv > 0) {
/* Re-invert the value, so MOVK sees non-inverted bits. */
value = ~value;
/* Clear out all the 0xffff lanes. */
value ^= imask;
}
/* Clear out the lane that we just set. */
value &= ~(0xffffUL << shift);
/* Iterate until all lanes have been set, and thus cleared from VALUE. */
while (value) {
shift = ctz64(value) & (63 & -16);
tcg_out_insn(s, 3405, MOVK, type, rd, value >> shift, shift);
value &= ~(0xffffUL << shift);
insn = I3405_MOVK;
} while (value);
}
}
static inline void tcg_out_ldst_r(TCGContext *s,