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target-s390: Optimize get_address

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Don't load the displacement into a register first, add it second
so that tcg_gen_addi_i64 can eliminate zeros.  Don't mask the
displacement first so that we don't turn small negative numbers
into large positive numbers.

Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2012-09-21 06:57:09 -07:00
parent c95ec459c6
commit bacf43c62e
1 changed files with 18 additions and 26 deletions
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42
target-s390x/translate.c
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@ -331,37 +331,29 @@ static inline void check_privileged(DisasContext *s)
static TCGv_i64 get_address(DisasContext *s, int x2, int b2, int d2)
{
TCGv_i64 tmp;
TCGv_i64 tmp = tcg_temp_new_i64();
bool need_31 = !(s->tb->flags & FLAG_MASK_64);
/* 31-bitify the immediate part; register contents are dealt with below */
if (!(s->tb->flags & FLAG_MASK_64)) {
d2 &= 0x7fffffffUL;
}
/* Note that d2 is limited to 20 bits, signed. If we crop negative
displacements early we create larger immedate addends. */
if (x2) {
if (d2) {
tmp = tcg_const_i64(d2);
tcg_gen_add_i64(tmp, tmp, regs[x2]);
} else {
tmp = load_reg(x2);
}
if (b2) {
tcg_gen_add_i64(tmp, tmp, regs[b2]);
}
/* Note that addi optimizes the imm==0 case. */
if (b2 && x2) {
tcg_gen_add_i64(tmp, regs[b2], regs[x2]);
tcg_gen_addi_i64(tmp, tmp, d2);
} else if (b2) {
if (d2) {
tmp = tcg_const_i64(d2);
tcg_gen_add_i64(tmp, tmp, regs[b2]);
tcg_gen_addi_i64(tmp, regs[b2], d2);
} else if (x2) {
tcg_gen_addi_i64(tmp, regs[x2], d2);
} else {
tmp = load_reg(b2);
if (need_31) {
d2 &= 0x7fffffff;
need_31 = false;
}
} else {
tmp = tcg_const_i64(d2);
tcg_gen_movi_i64(tmp, d2);
}
/* 31-bit mode mask if there are values loaded from registers */
if (!(s->tb->flags & FLAG_MASK_64) && (x2 || b2)) {
tcg_gen_andi_i64(tmp, tmp, 0x7fffffffUL);
if (need_31) {
tcg_gen_andi_i64(tmp, tmp, 0x7fffffff);
}
return tmp;