target/s390x: Simplify help_branch
Always use a tcg branch, instead of movcond. The movcond
was not a bad idea before PER was added, but since then
we have either 2 or 3 actions to perform on each leg of
the branch, and multiple movcond is inefficient.
Reorder the taken branch to be fallthrough of the tcg branch.
Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240502054417.234340-8-richard.henderson@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/target/s390x/tcg/translate.c b/target/s390x/tcg/translate.c
index 7ae928c..78066aa 100644
--- a/target/s390x/tcg/translate.c
+++ b/target/s390x/tcg/translate.c
@@ -353,25 +353,6 @@
#endif
}
-static void per_branch_cond(DisasContext *s, TCGCond cond,
- TCGv_i64 arg1, TCGv_i64 arg2)
-{
-#ifndef CONFIG_USER_ONLY
- if (s->base.tb->flags & FLAG_MASK_PER_BRANCH) {
- TCGLabel *lab = gen_new_label();
- tcg_gen_brcond_i64(tcg_invert_cond(cond), arg1, arg2, lab);
-
- tcg_gen_movi_i64(gbea, s->base.pc_next);
- gen_helper_per_branch(tcg_env, gbea, psw_addr);
-
- gen_set_label(lab);
- } else {
- TCGv_i64 pc = tcg_constant_i64(s->base.pc_next);
- tcg_gen_movcond_i64(cond, gbea, arg1, arg2, gbea, pc);
- }
-#endif
-}
-
static void per_breaking_event(DisasContext *s)
{
tcg_gen_movi_i64(gbea, s->base.pc_next);
@@ -1128,14 +1109,12 @@
static DisasJumpType help_branch(DisasContext *s, DisasCompare *c,
bool is_imm, int imm, TCGv_i64 cdest)
{
- DisasJumpType ret;
uint64_t dest = s->base.pc_next + (int64_t)imm * 2;
- TCGLabel *lab;
+ TCGLabel *lab, *over;
/* Take care of the special cases first. */
if (c->cond == TCG_COND_NEVER) {
- ret = DISAS_NEXT;
- goto egress;
+ return DISAS_NEXT;
}
if (is_imm) {
/*
@@ -1145,104 +1124,73 @@
if (c->cond == TCG_COND_ALWAYS
|| (dest == s->pc_tmp &&
!(s->base.tb->flags & FLAG_MASK_PER_BRANCH))) {
- ret = help_goto_direct(s, dest);
- goto egress;
+ return help_goto_direct(s, dest);
}
} else {
if (!cdest) {
/* E.g. bcr %r0 -> no branch. */
- ret = DISAS_NEXT;
- goto egress;
+ return DISAS_NEXT;
}
if (c->cond == TCG_COND_ALWAYS) {
- ret = help_goto_indirect(s, cdest);
- goto egress;
+ return help_goto_indirect(s, cdest);
}
}
- if (use_goto_tb(s, s->pc_tmp)) {
- if (is_imm && use_goto_tb(s, dest)) {
- /* Both exits can use goto_tb. */
- update_cc_op(s);
+ update_cc_op(s);
- lab = gen_new_label();
- if (c->is_64) {
- tcg_gen_brcond_i64(c->cond, c->u.s64.a, c->u.s64.b, lab);
- } else {
- tcg_gen_brcond_i32(c->cond, c->u.s32.a, c->u.s32.b, lab);
- }
-
- /* Branch not taken. */
- tcg_gen_goto_tb(0);
- tcg_gen_movi_i64(psw_addr, s->pc_tmp);
- tcg_gen_exit_tb(s->base.tb, 0);
-
- /* Branch taken. */
- gen_set_label(lab);
- per_breaking_event(s);
- tcg_gen_goto_tb(1);
- tcg_gen_movi_i64(psw_addr, dest);
- tcg_gen_exit_tb(s->base.tb, 1);
-
- ret = DISAS_NORETURN;
- } else {
- /* Fallthru can use goto_tb, but taken branch cannot. */
- /* Store taken branch destination before the brcond. This
- avoids having to allocate a new local temp to hold it.
- We'll overwrite this in the not taken case anyway. */
- if (!is_imm) {
- tcg_gen_mov_i64(psw_addr, cdest);
- }
-
- lab = gen_new_label();
- if (c->is_64) {
- tcg_gen_brcond_i64(c->cond, c->u.s64.a, c->u.s64.b, lab);
- } else {
- tcg_gen_brcond_i32(c->cond, c->u.s32.a, c->u.s32.b, lab);
- }
-
- /* Branch not taken. */
- update_cc_op(s);
- tcg_gen_goto_tb(0);
- tcg_gen_movi_i64(psw_addr, s->pc_tmp);
- tcg_gen_exit_tb(s->base.tb, 0);
-
- gen_set_label(lab);
- if (is_imm) {
- tcg_gen_movi_i64(psw_addr, dest);
- }
- per_breaking_event(s);
- ret = DISAS_PC_UPDATED;
- }
+ /*
+ * Ensure the taken branch is fall-through of the tcg branch.
+ * This keeps @cdest usage within the extended basic block,
+ * which avoids an otherwise unnecessary spill to the stack.
+ */
+ lab = gen_new_label();
+ if (s->base.tb->flags & FLAG_MASK_PER_BRANCH) {
+ over = gen_new_label();
} else {
- /* Fallthru cannot use goto_tb. This by itself is vanishingly rare.
- Most commonly we're single-stepping or some other condition that
- disables all use of goto_tb. Just update the PC and exit. */
-
- TCGv_i64 next = tcg_constant_i64(s->pc_tmp);
- if (is_imm) {
- cdest = tcg_constant_i64(dest);
- }
-
- if (c->is_64) {
- tcg_gen_movcond_i64(c->cond, psw_addr, c->u.s64.a, c->u.s64.b,
- cdest, next);
- per_branch_cond(s, c->cond, c->u.s64.a, c->u.s64.b);
- } else {
- TCGv_i32 t0 = tcg_temp_new_i32();
- TCGv_i64 t1 = tcg_temp_new_i64();
- TCGv_i64 z = tcg_constant_i64(0);
- tcg_gen_setcond_i32(c->cond, t0, c->u.s32.a, c->u.s32.b);
- tcg_gen_extu_i32_i64(t1, t0);
- tcg_gen_movcond_i64(TCG_COND_NE, psw_addr, t1, z, cdest, next);
- per_branch_cond(s, TCG_COND_NE, t1, z);
- }
-
- ret = DISAS_PC_UPDATED;
+ over = NULL;
}
- egress:
- return ret;
+ if (c->is_64) {
+ tcg_gen_brcond_i64(tcg_invert_cond(c->cond),
+ c->u.s64.a, c->u.s64.b, lab);
+ } else {
+ tcg_gen_brcond_i32(tcg_invert_cond(c->cond),
+ c->u.s32.a, c->u.s32.b, lab);
+ }
+
+ /* Branch taken. */
+ if (is_imm) {
+ tcg_gen_movi_i64(psw_addr, dest);
+ } else {
+ tcg_gen_mov_i64(psw_addr, cdest);
+ }
+ per_branch(s, false);
+
+ if (is_imm && use_goto_tb(s, dest)) {
+ tcg_gen_goto_tb(0);
+ tcg_gen_exit_tb(s->base.tb, 0);
+ } else if (over) {
+ tcg_gen_br(over);
+ } else {
+ tcg_gen_lookup_and_goto_ptr();
+ }
+
+ gen_set_label(lab);
+
+ /* Branch not taken. */
+ tcg_gen_movi_i64(psw_addr, s->pc_tmp);
+ if (use_goto_tb(s, s->pc_tmp)) {
+ tcg_gen_goto_tb(1);
+ tcg_gen_exit_tb(s->base.tb, 1);
+ }
+
+ if (over) {
+ gen_set_label(over);
+ return DISAS_PC_UPDATED;
+ }
+
+ tcg_gen_lookup_and_goto_ptr();
+ return DISAS_NORETURN;
}
/* ====================================================================== */
