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tcg-s390: Improve setcond 

There are a variety of common cases for which we can use carry tricks to
avoid a conditional branch.  On very new hardware, use LOAD ON CONDITION
instead of a conditional branch.

Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2014-03-31 12:57:06 -04:00
parent ad19b35808
commit 7b7066b1db
1 changed files with 91 additions and 6 deletions
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97
tcg/s390/tcg-target.c
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@ -1135,15 +1135,100 @@ static int tgen_cmp(TCGContext *s, TCGType type, TCGCond c, TCGReg r1,
return tcg_cond_to_s390_cond[c];
}
static void tgen_setcond(TCGContext *s, TCGType type, TCGCond c,
static void tgen_setcond(TCGContext *s, TCGType type, TCGCond cond,
TCGReg dest, TCGReg c1, TCGArg c2, int c2const)
{
int cc = tgen_cmp(s, type, c, c1, c2, c2const);
int cc;
/* Emit: r1 = 1; if (cc) goto over; r1 = 0; over: */
tcg_out_movi(s, type, dest, 1);
tcg_out_insn(s, RI, BRC, cc, (4 + 4) >> 1);
tcg_out_movi(s, type, dest, 0);
switch (cond) {
case TCG_COND_GTU:
case TCG_COND_GT:
do_greater:
/* The result of a compare has CC=2 for GT and CC=3 unused.
ADD LOGICAL WITH CARRY considers (CC & 2) the carry bit. */
tgen_cmp(s, type, cond, c1, c2, c2const);
tcg_out_movi(s, type, dest, 0);
tcg_out_insn(s, RRE, ALCGR, dest, dest);
return;
case TCG_COND_GEU:
do_geu:
/* We need "real" carry semantics, so use SUBTRACT LOGICAL
instead of COMPARE LOGICAL. This needs an extra move. */
tcg_out_mov(s, type, TCG_TMP0, c1);
if (c2const) {
tcg_out_movi(s, TCG_TYPE_I64, dest, 0);
if (type == TCG_TYPE_I32) {
tcg_out_insn(s, RIL, SLFI, TCG_TMP0, c2);
} else {
tcg_out_insn(s, RIL, SLGFI, TCG_TMP0, c2);
}
} else {
if (type == TCG_TYPE_I32) {
tcg_out_insn(s, RR, SLR, TCG_TMP0, c2);
} else {
tcg_out_insn(s, RRE, SLGR, TCG_TMP0, c2);
}
tcg_out_movi(s, TCG_TYPE_I64, dest, 0);
}
tcg_out_insn(s, RRE, ALCGR, dest, dest);
return;
case TCG_COND_LEU:
case TCG_COND_LTU:
case TCG_COND_LT:
/* Swap operands so that we can use GEU/GTU/GT. */
if (c2const) {
tcg_out_movi(s, type, TCG_TMP0, c2);
c2 = c1;
c2const = 0;
c1 = TCG_TMP0;
} else {
TCGReg t = c1;
c1 = c2;
c2 = t;
}
if (cond == TCG_COND_LEU) {
goto do_geu;
}
cond = tcg_swap_cond(cond);
goto do_greater;
case TCG_COND_NE:
/* X != 0 is X > 0. */
if (c2const && c2 == 0) {
cond = TCG_COND_GTU;
goto do_greater;
}
break;
case TCG_COND_EQ:
/* X == 0 is X <= 0 is 0 >= X. */
if (c2const && c2 == 0) {
tcg_out_movi(s, TCG_TYPE_I64, TCG_TMP0, 0);
c2 = c1;
c2const = 0;
c1 = TCG_TMP0;
goto do_geu;
}
break;
default:
break;
}
cc = tgen_cmp(s, type, cond, c1, c2, c2const);
if (facilities & FACILITY_LOAD_ON_COND) {
/* Emit: d = 0, t = 1, d = (cc ? t : d). */
tcg_out_movi(s, TCG_TYPE_I64, dest, 0);
tcg_out_movi(s, TCG_TYPE_I64, TCG_TMP0, 1);
tcg_out_insn(s, RRF, LOCGR, dest, TCG_TMP0, cc);
} else {
/* Emit: d = 1; if (cc) goto over; d = 0; over: */
tcg_out_movi(s, type, dest, 1);
tcg_out_insn(s, RI, BRC, cc, (4 + 4) >> 1);
tcg_out_movi(s, type, dest, 0);
}
}
static void tgen_movcond(TCGContext *s, TCGType type, TCGCond c, TCGReg dest,