From c56caea3b2a4ef5d760266f554df0d92c5a45f87 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Tue, 3 Nov 2020 13:20:21 -0800 Subject: tcg: Revert "tcg/optimize: Flush data at labels not TCG_OPF_BB_END" This reverts commit cd0372c515c4732d8bd3777cdd995c139c7ed7ea. 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 Signed-off-by: Richard Henderson --- tcg/optimize.c | 35 +++++++++++++++++------------------ 1 file changed, 17 insertions(+), 18 deletions(-) (limited to 'tcg') diff --git a/tcg/optimize.c b/tcg/optimize.c index 9952c28bdc..220f4601d5 100644 --- a/tcg/optimize.c +++ b/tcg/optimize.c @@ -1484,30 +1484,29 @@ 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. - */ - 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). - */ - if (i == 0) { - arg_info(op->args[i])->mask = mask; + /* 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). */ + 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; } /* Eliminate duplicate and redundant fence instructions. */ -- cgit v1.2.3