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tcg/i386: use 8-bit OR or XOR for unsigned 8-bit immediates

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In the case where OR or XOR has an 8-bit immediate between 128 and 255,
we can operate on a low-byte register and shorten the output by two or
three bytes (two if a prefix byte is needed for REX.B).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20231228120524.70239-1-pbonzini@redhat.com>
[rth: Incorporate into switch.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Paolo Bonzini 2023-12-28 13:05:24 +01:00 committed by Richard Henderson
parent 64708db302
commit afa37be4b4
1 changed files with 11 additions and 0 deletions
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11
tcg/i386/tcg-target.c.inc
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@ -244,6 +244,7 @@ static bool tcg_target_const_match(int64_t val, TCGType type, int ct, int vece)
#define P_VEXL 0x80000 /* Set VEX.L = 1 */
#define P_EVEX 0x100000 /* Requires EVEX encoding */
#define OPC_ARITH_EbIb (0x80)
#define OPC_ARITH_EvIz (0x81)
#define OPC_ARITH_EvIb (0x83)
#define OPC_ARITH_GvEv (0x03) /* ... plus (ARITH_FOO << 3) */
@ -1370,6 +1371,16 @@ static void tgen_arithi(TCGContext *s, int c, int r0,
return;
}
break;
case ARITH_OR:
case ARITH_XOR:
if (val >= 0x80 && val <= 0xff
&& (r0 < 4 || TCG_TARGET_REG_BITS == 64)) {
tcg_out_modrm(s, OPC_ARITH_EbIb + P_REXB_RM, c, r0);
tcg_out8(s, val);
return;
}
break;
}
if (val == (int8_t)val) {