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 <r...@twiddle.net>
---
tcg/s390/tcg-target.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 91 insertions(+), 6 deletions(-)
diff --git a/tcg/s390/tcg-target.c b/tcg/s390/tcg-target.c
index 54d6dc1..132f71a 100644
--- a/tcg/s390/tcg-target.c
+++ b/tcg/s390/tcg-target.c
@@ -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;
+
+ 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;
- /* 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);
+ 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,
--
1.9.0
