One effect of https://gcc.gnu.org/ml/gcc-patches/2019-09/msg00802.html
was to strengthen the sanity check in lra_assigns so that it checks
whether reg_renumber is consistent with the whole conflict set.
This duly tripped on csky for a pseudo that had been allocated
to the eliminated frame pointer. (csky doesn't have a separate
hard frame pointer.)
lra-lives uses:
/* Set of hard regs (except eliminable ones) currently live. */
static HARD_REG_SET hard_regs_live;
to track the set of live directly-referenced hard registers, and it
correctly implements the exclusion when setting up the initial set:
hard_regs_live &= ~eliminable_regset;
But later calls to make_hard_regno_live and make_hard_regno_dead
would process eliminable registers like other registers, recording
conflicts for them and potentially making them live. (Note that
after r266086, make_hard_regno_dead adds conflicts for registers
that are already marked dead.) I think this would have had the
effect of pessimising targets without a separate hard frame pointer.
Tested on aarch64-linux-gnu (where it probably doesn't do much)
and against the testcase on csky-linux-gnu. OK to install?
Richard
2019-10-01 Richard Sandiford <richard.sandif...@arm.com>
gcc/
PR middle-end/91957
* lra-lives.c (make_hard_regno_dead): Don't record conflicts for
eliminable registers.
(make_hard_regno_live): Likewise, and don't make them live.
Index: gcc/lra-lives.c
===================================================================
--- gcc/lra-lives.c 2019-10-01 09:55:35.146088630 +0100
+++ gcc/lra-lives.c 2019-10-01 23:36:02.545946185 +0100
@@ -281,7 +281,8 @@ update_pseudo_point (int regno, int poin
make_hard_regno_live (int regno)
{
lra_assert (HARD_REGISTER_NUM_P (regno));
- if (TEST_HARD_REG_BIT (hard_regs_live, regno))
+ if (TEST_HARD_REG_BIT (hard_regs_live, regno)
+ || TEST_HARD_REG_BIT (eliminable_regset, regno))
return;
SET_HARD_REG_BIT (hard_regs_live, regno);
sparseset_set_bit (start_living, regno);
@@ -295,6 +296,9 @@ make_hard_regno_live (int regno)
static void
make_hard_regno_dead (int regno)
{
+ if (TEST_HARD_REG_BIT (eliminable_regset, regno))
+ return;
+
lra_assert (HARD_REGISTER_NUM_P (regno));
unsigned int i;
EXECUTE_IF_SET_IN_SPARSESET (pseudos_live, i)
