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tcg/optimize: fix known-zero bits optimization

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Known-zero bits optimization is a great idea that helps to generate more
optimized code. However the current implementation only works in very few
cases as the computed mask is not saved.

Fix this to make it really working.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Aurelien Jarno 2013-09-03 08:27:38 +02:00 committed by Richard Henderson
parent e46b225a31
commit 3031244b01
1 changed files with 7 additions and 1 deletions
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8
tcg/optimize.c
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@ -691,7 +691,8 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
break;
}
/* Simplify using known-zero bits */
/* Simplify using known-zero bits. Currently only ops with a single
output argument is supported. */
mask = -1;
affected = -1;
switch (op) {
@ -1149,6 +1150,11 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
} else {
for (i = 0; i < def->nb_oargs; i++) {
reset_temp(args[i]);
/* Save the corresponding known-zero bits mask for the
first output argument (only one supported so far). */
if (i == 0) {
temps[args[i]].mask = mask;
}
}
}
for (i = 0; i < def->nb_args; i++) {