From e83714f65d1f75fc5af39f9fdc520a909dfc7635 Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Sat, 4 Apr 2020 17:23:40 +0100 Subject: [PATCH] lra: Stop eh_return data regs being incorrectly marked live [PR92989] lra_assign has an assert to make sure that no pseudo is allocated to a conflicting hard register. It used to be restricted to !flag_ipa_ra, but in g:a1e6ee38e708ef2bdef4 I'd enabled it for flag_ipa_ra too. It then tripped a few times while building libstdc++ for mips-mti-linux. Previous patches fixed one of the problems: registers clobbered by the taking of an exception were being treated as live at the beginning of the EH receiver, and this got propagated to predecessor blocks. But it turns out that there was a second problem: eh_return data registers were also being marked live in the same way. These registers are defined by the unwinder and so in reality they are live on entry to the EH receiver. But definitions can only happen in blocks, not on edges, so for liveness purposes we use artificial definitions at the start of the EH receiver. process_bb_lives should therefore model the effect of a definition, not a plain use. 2020-04-06 Richard Sandiford gcc/ PR rtl-optimization/92989 * lra-lives.c (process_bb_lives): Do not treat eh_return data registers as being live at the beginning of the EH receiver. --- gcc/ChangeLog | 6 ++++++ gcc/lra-lives.c | 6 ++++++ 2 files changed, 12 insertions(+) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index e10fb251c16..258e9dbc956 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2020-04-06 Richard Sandiford + + PR rtl-optimization/92989 + * lra-lives.c (process_bb_lives): Do not treat eh_return data + registers as being live at the beginning of the EH receiver. + 2020-04-05 Zachary Spytz * extend.texi: Add free to list of ISO C90 functions that diff --git a/gcc/lra-lives.c b/gcc/lra-lives.c index c8780779a11..917c617903f 100644 --- a/gcc/lra-lives.c +++ b/gcc/lra-lives.c @@ -1014,13 +1014,19 @@ process_bb_lives (basic_block bb, int &curr_point, bool dead_insn_p) } if (bb_has_eh_pred (bb)) + /* Any pseudos that are currently live conflict with the eh_return + data registers. For liveness purposes, these registers are set + by artificial definitions at the start of the BB, so are not + actually live on entry. */ for (j = 0; ; ++j) { unsigned int regno = EH_RETURN_DATA_REGNO (j); if (regno == INVALID_REGNUM) break; + make_hard_regno_live (regno); + make_hard_regno_dead (regno); } /* Pseudos can't go in stack regs at the start of a basic block that -- 2.30.2