This patch fixes a corner case in the AMD GCN md-reorg pass when the
EXEC register is live on entry to a BB, and could be clobbered by code
inserted by the pass before a use in (e.g.) a different BB.
I don't have a standalone test case demonstrating this failure mode,
but I did observe it with an offload compiler (on another branch) with
a particular benchmark.
Tested with standalone AMD GCN target. I will commit shortly.
Julian
2021-01-13 Julian Brown <jul...@codesourcery.com>
gcc/
* config/gcn/gcn.c (gcn_md_reorg): Fix case where EXEC reg is live
on entry to a BB.
---
gcc/config/gcn/gcn.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/gcc/config/gcn/gcn.c b/gcc/config/gcn/gcn.c
index 0fb9bd26727..630ce4eebc7 100644
--- a/gcc/config/gcn/gcn.c
+++ b/gcc/config/gcn/gcn.c
@@ -4501,6 +4501,8 @@ gcn_md_reorg (void)
df_insn_rescan_all ();
}
+ df_live_add_problem ();
+ df_live_set_all_dirty ();
df_analyze ();
/* This pass ensures that the EXEC register is set correctly, according
@@ -4522,6 +4524,17 @@ gcn_md_reorg (void)
int64_t curr_exec = 0; /* 0 here means 'the value is that of EXEC
after last_exec_def is executed'. */
+ bitmap live_in = DF_LR_IN (bb);
+ bool exec_live_on_entry = false;
+ if (bitmap_bit_p (live_in, EXEC_LO_REG)
+ || bitmap_bit_p (live_in, EXEC_HI_REG))
+ {
+ if (dump_file)
+ fprintf (dump_file, "EXEC reg is live on entry to block %d\n",
+ (int) bb->index);
+ exec_live_on_entry = true;
+ }
+
FOR_BB_INSNS_SAFE (bb, insn, curr)
{
if (!NONDEBUG_INSN_P (insn))
@@ -4660,6 +4673,8 @@ gcn_md_reorg (void)
exec_lo_def_p == exec_hi_def_p ? "full" : "partial",
INSN_UID (insn));
}
+
+ exec_live_on_entry = false;
}
COPY_REG_SET (&live, DF_LR_OUT (bb));
@@ -4669,7 +4684,7 @@ gcn_md_reorg (void)
at the end of the block. */
if ((REGNO_REG_SET_P (&live, EXEC_LO_REG)
|| REGNO_REG_SET_P (&live, EXEC_HI_REG))
- && (!curr_exec_known || !curr_exec_explicit))
+ && (!curr_exec_known || !curr_exec_explicit || exec_live_on_entry))
{
rtx_insn *end_insn = BB_END (bb);
--
2.29.2
