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tcg-optimize: Fold sub r,0,x to neg r,x

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Cc: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
This commit is contained in:
Richard Henderson 2013-03-21 09:13:33 -07:00 committed by Blue Swirl
parent 4980ef9e3e
commit 2d497542e1
1 changed files with 33 additions and 1 deletions
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34
tcg/optimize.c
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@ -576,7 +576,8 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
break;
}
/* Simplify expressions for "shift/rot r, 0, a => movi r, 0" */
/* Simplify expressions for "shift/rot r, 0, a => movi r, 0",
and "sub r, 0, a => neg r, a" case. */
switch (op) {
CASE_OP_32_64(shl):
CASE_OP_32_64(shr):
@ -592,6 +593,37 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
continue;
}
break;
CASE_OP_32_64(sub):
{
TCGOpcode neg_op;
bool have_neg;
if (temps[args[2]].state == TCG_TEMP_CONST) {
/* Proceed with possible constant folding. */
break;
}
if (op == INDEX_op_sub_i32) {
neg_op = INDEX_op_neg_i32;
have_neg = TCG_TARGET_HAS_neg_i32;
} else {
neg_op = INDEX_op_neg_i64;
have_neg = TCG_TARGET_HAS_neg_i64;
}
if (!have_neg) {
break;
}
if (temps[args[1]].state == TCG_TEMP_CONST
&& temps[args[1]].val == 0) {
s->gen_opc_buf[op_index] = neg_op;
reset_temp(args[0]);
gen_args[0] = args[0];
gen_args[1] = args[2];
args += 3;
gen_args += 2;
continue;
}
}
break;
default:
break;
}