s390: Do not waste a register when assigning a constant to a memory
location. If available, use MVHI and friends. If those are not available,
load the constant value into register r0 and store that. r0 is not visible
to register allocation and therefore using it does not increase register
pressure.
Remove S390_INSN_MZERO and replace it with S390_INSN_MIMM. Assigning zero
is just a special case..
Saves between 0.9% and 2.4% of insns as measured with the perf regression
bucket.
git-svn-id: svn://svn.valgrind.org/vex/trunk@2619 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/host_s390_isel.c b/priv/host_s390_isel.c
index 3027045..ce81cee 100644
--- a/priv/host_s390_isel.c
+++ b/priv/host_s390_isel.c
@@ -426,6 +426,24 @@
}
+/* Return the value of CON as a sign-exteded ULong value */
+static ULong
+get_const_value_as_ulong(const IRConst *con)
+{
+ Long value;
+
+ switch (con->tag) {
+ case Ico_U1: value = con->Ico.U1; return (ULong) ((value << 63) >> 63);
+ case Ico_U8: value = con->Ico.U8; return (ULong) ((value << 56) >> 56);
+ case Ico_U16: value = con->Ico.U16; return (ULong) ((value << 48) >> 48);
+ case Ico_U32: value = con->Ico.U32; return (ULong) ((value << 32) >> 32);
+ case Ico_U64: return con->Ico.U64;
+ default:
+ vpanic("get_const_value_as_ulong");
+ }
+}
+
+
/* Call a helper (clean or dirty)
Arguments must satisfy the following conditions:
@@ -2924,8 +2942,10 @@
case Ity_I64:
/* fixs390: We could check for INSN_MADD here. */
if (am->tag == S390_AMODE_B12 &&
- s390_expr_is_const_zero(stmt->Ist.Store.data)) {
- addInstr(env, s390_insn_mzero(sizeofIRType(tyd), am));
+ stmt->Ist.Store.data->tag == Iex_Const) {
+ ULong value =
+ get_const_value_as_ulong(stmt->Ist.Store.data->Iex.Const.con);
+ addInstr(env, s390_insn_mimm(sizeofIRType(tyd), am, value));
return;
}
src = s390_isel_int_expr(env, stmt->Ist.Store.data);
@@ -3000,13 +3020,6 @@
return;
}
- /* guest register = 0 */
- if (new_value == 0) {
- am = s390_amode_for_guest_state(offset);
- addInstr(env, s390_insn_mzero(sizeofIRType(tyd), am));
- return;
- }
-
if (old_value_is_valid == False) goto not_special;
/* If the new value is in the neighbourhood of the old value
@@ -3020,22 +3033,17 @@
return;
}
- /* If the high word is the same it is sufficient to load the low word.
- Use R0 as a scratch reg. */
+ /* If the high word is the same it is sufficient to load the low word. */
if ((old_value >> 32) == (new_value >> 32)) {
- HReg r0 = make_gpr(0);
-
am = s390_amode_for_guest_state(offset + 4);
- addInstr(env, s390_insn_load_immediate(4, r0,
- new_value & 0xFFFFFFFF));
- addInstr(env, s390_insn_store(4, am, r0));
+ addInstr(env, s390_insn_mimm(4, am, new_value & 0xFFFFFFFF));
return;
}
/* No special case applies... fall through */
not_special:
- am = s390_amode_for_guest_state(stmt->Ist.Put.offset);
+ am = s390_amode_for_guest_state(offset);
switch (tyd) {
case Ity_I8:
@@ -3043,8 +3051,10 @@
case Ity_I32:
case Ity_I64:
if (am->tag == S390_AMODE_B12 &&
- s390_expr_is_const_zero(stmt->Ist.Put.data)) {
- addInstr(env, s390_insn_mzero(sizeofIRType(tyd), am));
+ stmt->Ist.Put.data->tag == Iex_Const) {
+ ULong value =
+ get_const_value_as_ulong(stmt->Ist.Put.data->Iex.Const.con);
+ addInstr(env, s390_insn_mimm(sizeofIRType(tyd), am, value));
return;
}
src = s390_isel_int_expr(env, stmt->Ist.Put.data);