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tcg: Revert "tcg/optimize: Flush data at labels not TCG_OPF_BB_END"

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This reverts commit cd0372c515.

The patch is incorrect in that it retains copies between globals and
non-local temps, and non-local temps still die at the end of the BB.

Failing test case for hppa:

	.globl	_start
_start:
	cmpiclr,=	0x24,%r19,%r0
	cmpiclr,<>	0x2f,%r19,%r19

 ---- 00010057 0001005b
 movi_i32 tmp0,$0x24
 sub_i32 tmp1,tmp0,r19
 mov_i32 tmp2,tmp0
 mov_i32 tmp3,r19
 movi_i32 tmp1,$0x0

 ---- 0001005b 0001005f
 brcond_i32 tmp2,tmp3,eq,$L1
 movi_i32 tmp0,$0x2f
 sub_i32 tmp1,tmp0,r19
 mov_i32 tmp2,tmp0
 mov_i32 tmp3,r19
 movi_i32 tmp1,$0x0
 mov_i32 r19,tmp1
 setcond_i32 psw_n,tmp2,tmp3,ne
 set_label $L1

In this case, both copies of "mov_i32 tmp3,r19" are removed.  The
second because opt thought it was redundant.  The first is removed
later by liveness because tmp3 is known to be dead.  This leaves
the setcond_i32 with an uninitialized input.

Revert the entire patch for 5.2, and a proper optimization across
the branch may be considered for the next development cycle.

Reported-by: qemu@igor2.repo.hu
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2020-11-03 13:20:21 -08:00
parent f14bed3fd4
commit c56caea3b2
1 changed files with 17 additions and 18 deletions
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27
tcg/optimize.c
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@ -1484,29 +1484,28 @@ void tcg_optimize(TCGContext *s)
}
}
}
/* fall through */
goto do_reset_output;
default:
do_default:
/*
* Default case: we know nothing about operation (or were unable
* to compute the operation result) so no propagation is done.
*/
/* Default case: we know nothing about operation (or were unable
to compute the operation result) so no propagation is done.
We trash everything if the operation is the end of a basic
block, otherwise we only trash the output args. "mask" is
the non-zero bits mask for the first output arg. */
if (def->flags & TCG_OPF_BB_END) {
bitmap_zero(temps_used.l, nb_temps);
} else {
do_reset_output:
for (i = 0; i < nb_oargs; i++) {
reset_temp(op->args[i]);
/*
* Save the corresponding known-zero bits mask for the
* first output argument (only one supported so far).
*/
/* Save the corresponding known-zero bits mask for the
first output argument (only one supported so far). */
if (i == 0) {
arg_info(op->args[i])->mask = mask;
}
}
break;
case INDEX_op_set_label:
/* Trash everything at the start of a new extended bb. */
bitmap_zero(temps_used.l, nb_temps);
}
break;
}