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tcg-aarch64: Prefer unsigned offsets before signed offsets for ldst 

The assembler seems to prefer them, perhaps we should too.

Reviewed-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2014-03-03 23:03:51 -05:00 committed by Richard Henderson
parent 3d4299f425
commit a056c9faa4
1 changed files with 6 additions and 5 deletions
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11
tcg/aarch64/tcg-target.c
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@ -669,11 +669,6 @@ static void tcg_out_ldst(TCGContext *s, AArch64Insn insn,
{ {
TCGMemOp size = (uint32_t)insn >> 30; TCGMemOp size = (uint32_t)insn >> 30;
if (offset >= -256 && offset < 256) {
tcg_out_insn_3312(s, insn, rd, rn, offset);
return;
}
/* If the offset is naturally aligned and in range, then we can /* If the offset is naturally aligned and in range, then we can
use the scaled uimm12 encoding */ use the scaled uimm12 encoding */
if (offset >= 0 && !(offset & ((1 << size) - 1))) { if (offset >= 0 && !(offset & ((1 << size) - 1))) {
@ -684,6 +679,12 @@ static void tcg_out_ldst(TCGContext *s, AArch64Insn insn,
} }
} }
/* Small signed offsets can use the unscaled encoding. */
if (offset >= -256 && offset < 256) {
tcg_out_insn_3312(s, insn, rd, rn, offset);
return;
}
/* Worst-case scenario, move offset to temp register, use reg offset. */ /* Worst-case scenario, move offset to temp register, use reg offset. */
tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_TMP, offset); tcg_out_movi(s, TCG_TYPE_I64, TCG_REG_TMP, offset);
tcg_out_ldst_r(s, insn, rd, rn, TCG_REG_TMP); tcg_out_ldst_r(s, insn, rd, rn, TCG_REG_TMP);