https://gcc.gnu.org/g:ae981f433d7186a9204a42050e3ae2a9472338a2
commit r15-10335-gae981f433d7186a9204a42050e3ae2a9472338a2 Author: Jeff Law <[email protected]> Date: Fri Sep 12 16:08:38 2025 -0600 Fix latent LRA bug 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. gcc/ * lra-constraints.cc (get_equiv): Bounds check before accessing data in ira_reg_equiv. (cherry picked from commit 0c6ad3f5dfbd45150eeef2474899ba7ef0d8e592) Diff: --- gcc/lra-constraints.cc | 1 + 1 file changed, 1 insertion(+) diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc index 630993819459..0cc9b3dbcb27 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)
