Shreya's work to add the addptr pattern on the RISC-V port exposed a
latent bug in LRA.
We lazily allocate/reallocate the ira_reg_equiv structure and when we do
(re)allocation we'll over-allocate and zero-fill so that we don't have
to actually allocate and relocate the data so often.
In the case exposed by Shreya's work we had N requested entries at the
last rellocation step. We actually allocate N+M entries. During LRA we
allocate enough new pseudos and thus have N+M+1 pseudos.
In get_equiv we read ira_reg_equiv[regno] without bounds checking so we
read past the allocated part of the array and get back junk which we use
and depending on the precise contents we fault in various fun and
interesting ways.
We could either arrange to re-allocate ira_reg_equiv again on some path
through LRA (possibly in get_equiv itself). We could also just insert
the bounds check in get_equiv like is done elsewhere in LRA. Vlad
indicated no strong preference in an email last week.
So this just adds the bounds check in a manner similar to what's done
elsewhere in LRA. Bootstrapped and regression tested on x86_64 as well
as RISC-V with Shreya's work enabled and regtested across the various
embedded targets.
OK for the trunk?
Jeff
gcc/
* lra-constraints.c (get_equiv): Bounds check before accessing
data in ira_reg_equiv.
diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 63099381945..0cc9b3dbcb2 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -541,6 +541,7 @@ get_equiv (rtx x)
rtx res;
if (! REG_P (x) || (regno = REGNO (x)) < FIRST_PSEUDO_REGISTER
+ || regno >= ira_reg_equiv_len
|| ! ira_reg_equiv[regno].defined_p
|| ! ira_reg_equiv[regno].profitable_p
|| lra_get_regno_hard_regno (regno) >= 0)
