[gcc r14-7132] aarch64: Fix dwarf2cfi ICEs due to recent CFI note changes [PR113077]
Alex Coplan
acoplan@gcc.gnu.org
Thu Jan 11 10:17:32 GMT 2024
https://gcc.gnu.org/g:5400778f69d19a94017561c7de02510d9c0899e6
commit r14-7132-g5400778f69d19a94017561c7de02510d9c0899e6
Author: Alex Coplan <alex.coplan@arm.com>
Date: Thu Jan 11 10:16:24 2024 +0000
aarch64: Fix dwarf2cfi ICEs due to recent CFI note changes [PR113077]
In r14-6604-gd7ee988c491cde43d04fe25f2b3dbad9d85ded45 we changed the CFI notes
attached to callee saves (in aarch64_save_callee_saves). That patch changed
the ldp/stp representation to use unspecs instead of PARALLEL moves. This meant
that we needed to attach CFI notes to all frame-related pair saves such that
dwarf2cfi could still emit the appropriate CFI (it cannot interpret the unspecs
directly). The patch also attached REG_CFA_OFFSET notes to individual saves so
that the ldp/stp pass could easily preserve them when forming stps.
In that change I chose to use REG_CFA_OFFSET, but as the PR shows, that
choice was problematic in that REG_CFA_OFFSET requires the attached
store to be expressed in terms of the current CFA register at all times.
This means that even scheduling of frame-related insns can break this
invariant, leading to ICEs in dwarf2cfi.
The old behaviour (before that change) allowed dwarf2cfi to interpret the RTL
directly for sp-relative saves. This change restores that behaviour by using
REG_FRAME_RELATED_EXPR instead of REG_CFA_OFFSET. REG_FRAME_RELATED_EXPR
effectively just gives a different pattern for dwarf2cfi to look at instead of
the main insn pattern. That allows us to attach the old-style PARALLEL move
representation in a REG_FRAME_RELATED_EXPR note and means we are free to always
express the save addresses in terms of the stack pointer.
Since the ldp/stp fusion pass can combine frame-related stores, this patch also
updates it to preserve REG_FRAME_RELATED_EXPR notes, and additionally gives it
the ability to synthesize those notes when combining sp-relative saves into an
stp (the latter always needs a note due to the unspec representation, the former
does not).
gcc/ChangeLog:
PR target/113077
* config/aarch64/aarch64-ldp-fusion.cc (filter_notes): Add
fr_expr param to extract REG_FRAME_RELATED_EXPR notes.
(combine_reg_notes): Handle REG_FRAME_RELATED_EXPR notes, and
synthesize these if needed. Update caller ...
(ldp_bb_info::fuse_pair): ... here.
(ldp_bb_info::try_fuse_pair): Punt if either insn has writeback
and either insn is frame-related.
(find_trailing_add): Punt on frame-related insns.
* config/aarch64/aarch64.cc (aarch64_save_callee_saves): Use
REG_FRAME_RELATED_EXPR instead of REG_CFA_OFFSET.
gcc/testsuite/ChangeLog:
PR target/113077
* gcc.target/aarch64/pr113077.c: New test.
Diff:
---
gcc/config/aarch64/aarch64-ldp-fusion.cc | 76 ++++++++++++++++++++++++++---
gcc/config/aarch64/aarch64.cc | 71 +++++++++++++++------------
gcc/testsuite/gcc.target/aarch64/pr113077.c | 11 +++++
3 files changed, 120 insertions(+), 38 deletions(-)
diff --git a/gcc/config/aarch64/aarch64-ldp-fusion.cc b/gcc/config/aarch64/aarch64-ldp-fusion.cc
index 2fe1b1d4d84..689a8c884bd 100644
--- a/gcc/config/aarch64/aarch64-ldp-fusion.cc
+++ b/gcc/config/aarch64/aarch64-ldp-fusion.cc
@@ -904,9 +904,11 @@ aarch64_operand_mode_for_pair_mode (machine_mode mode)
// Go through the reg notes rooted at NOTE, dropping those that we should drop,
// and preserving those that we want to keep by prepending them to (and
// returning) RESULT. EH_REGION is used to make sure we have at most one
-// REG_EH_REGION note in the resulting list.
+// REG_EH_REGION note in the resulting list. FR_EXPR is used to return any
+// REG_FRAME_RELATED_EXPR note we find, as these can need special handling in
+// combine_reg_notes.
static rtx
-filter_notes (rtx note, rtx result, bool *eh_region)
+filter_notes (rtx note, rtx result, bool *eh_region, rtx *fr_expr)
{
for (; note; note = XEXP (note, 1))
{
@@ -940,6 +942,10 @@ filter_notes (rtx note, rtx result, bool *eh_region)
copy_rtx (XEXP (note, 0)),
result);
break;
+ case REG_FRAME_RELATED_EXPR:
+ gcc_assert (!*fr_expr);
+ *fr_expr = copy_rtx (XEXP (note, 0));
+ break;
default:
// Unexpected REG_NOTE kind.
gcc_unreachable ();
@@ -950,14 +956,49 @@ filter_notes (rtx note, rtx result, bool *eh_region)
}
// Return the notes that should be attached to a combination of I1 and I2, where
-// *I1 < *I2.
+// *I1 < *I2. LOAD_P is true for loads.
static rtx
-combine_reg_notes (insn_info *i1, insn_info *i2)
+combine_reg_notes (insn_info *i1, insn_info *i2, bool load_p)
{
+ // Temporary storage for REG_FRAME_RELATED_EXPR notes.
+ rtx fr_expr[2] = {};
+
bool found_eh_region = false;
rtx result = NULL_RTX;
- result = filter_notes (REG_NOTES (i2->rtl ()), result, &found_eh_region);
- return filter_notes (REG_NOTES (i1->rtl ()), result, &found_eh_region);
+ result = filter_notes (REG_NOTES (i2->rtl ()), result,
+ &found_eh_region, fr_expr);
+ result = filter_notes (REG_NOTES (i1->rtl ()), result,
+ &found_eh_region, fr_expr + 1);
+
+ if (!load_p)
+ {
+ // Simple frame-related sp-relative saves don't need CFI notes, but when
+ // we combine them into an stp we will need a CFI note as dwarf2cfi can't
+ // interpret the unspec pair representation directly.
+ if (RTX_FRAME_RELATED_P (i1->rtl ()) && !fr_expr[0])
+ fr_expr[0] = copy_rtx (PATTERN (i1->rtl ()));
+ if (RTX_FRAME_RELATED_P (i2->rtl ()) && !fr_expr[1])
+ fr_expr[1] = copy_rtx (PATTERN (i2->rtl ()));
+ }
+
+ rtx fr_pat = NULL_RTX;
+ if (fr_expr[0] && fr_expr[1])
+ {
+ // Combining two frame-related insns, need to construct
+ // a REG_FRAME_RELATED_EXPR note which represents the combined
+ // operation.
+ RTX_FRAME_RELATED_P (fr_expr[1]) = 1;
+ fr_pat = gen_rtx_PARALLEL (VOIDmode,
+ gen_rtvec (2, fr_expr[0], fr_expr[1]));
+ }
+ else
+ fr_pat = fr_expr[0] ? fr_expr[0] : fr_expr[1];
+
+ if (fr_pat)
+ result = alloc_reg_note (REG_FRAME_RELATED_EXPR,
+ fr_pat, result);
+
+ return result;
}
// Given two memory accesses in PATS, at least one of which is of a
@@ -1049,6 +1090,14 @@ find_trailing_add (insn_info *insns[2],
poly_int64 initial_offset,
unsigned access_size)
{
+ // Punt on frame-related insns, it is better to be conservative and
+ // not try to form writeback pairs here, and means we don't have to
+ // worry about the writeback case in forming REG_FRAME_RELATED_EXPR
+ // notes (see combine_reg_notes).
+ if ((insns[0] && RTX_FRAME_RELATED_P (insns[0]->rtl ()))
+ || RTX_FRAME_RELATED_P (insns[1]->rtl ()))
+ return nullptr;
+
insn_info *pair_dst = pair_range.singleton ();
gcc_assert (pair_dst);
@@ -1380,7 +1429,7 @@ ldp_bb_info::fuse_pair (bool load_p,
return false;
}
- rtx reg_notes = combine_reg_notes (first, second);
+ rtx reg_notes = combine_reg_notes (first, second, load_p);
rtx pair_pat;
if (writeback_effect)
@@ -1987,6 +2036,19 @@ ldp_bb_info::try_fuse_pair (bool load_p, unsigned access_size,
return false;
}
+ // Punt on frame-related insns with writeback. We probably won't see
+ // these in practice, but this is conservative and ensures we don't
+ // have to worry about these later on.
+ if (writeback && (RTX_FRAME_RELATED_P (i1->rtl ())
+ || RTX_FRAME_RELATED_P (i2->rtl ())))
+ {
+ if (dump_file)
+ fprintf (dump_file,
+ "rejecting pair (%d,%d): frame-related insn with writeback\n",
+ i1->uid (), i2->uid ());
+ return false;
+ }
+
rtx *ignore = &XEXP (pats[1], load_p);
for (auto use : insns[1]->uses ())
if (!use->is_mem ()
diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index a5a6b52730d..32c7317f360 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -8465,7 +8465,7 @@ aarch64_save_callee_saves (poly_int64 bytes_below_sp,
emit_move_insn (move_src, gen_int_mode (aarch64_sve_vg, DImode));
}
rtx base_rtx = stack_pointer_rtx;
- poly_int64 cfa_offset = offset;
+ poly_int64 sp_offset = offset;
HOST_WIDE_INT const_offset;
if (mode == VNx2DImode && BYTES_BIG_ENDIAN)
@@ -8490,17 +8490,12 @@ aarch64_save_callee_saves (poly_int64 bytes_below_sp,
offset -= fp_offset;
}
rtx mem = gen_frame_mem (mode, plus_constant (Pmode, base_rtx, offset));
+ rtx cfi_mem = gen_frame_mem (mode, plus_constant (Pmode,
+ stack_pointer_rtx,
+ sp_offset));
+ rtx cfi_set = gen_rtx_SET (cfi_mem, reg);
+ bool need_cfi_note_p = (base_rtx != stack_pointer_rtx);
- rtx cfa_base = stack_pointer_rtx;
- if (hard_fp_valid_p && frame_pointer_needed)
- {
- cfa_base = hard_frame_pointer_rtx;
- cfa_offset += (bytes_below_sp - frame.bytes_below_hard_fp);
- }
-
- rtx cfa_mem = gen_frame_mem (mode,
- plus_constant (Pmode,
- cfa_base, cfa_offset));
unsigned int regno2;
if (!aarch64_sve_mode_p (mode)
&& reg == move_src
@@ -8514,34 +8509,48 @@ aarch64_save_callee_saves (poly_int64 bytes_below_sp,
offset += GET_MODE_SIZE (mode);
insn = emit_insn (aarch64_gen_store_pair (mem, reg, reg2));
- /* The first part of a frame-related parallel insn is
- always assumed to be relevant to the frame
- calculations; subsequent parts, are only
- frame-related if explicitly marked. */
+ rtx cfi_mem2
+ = gen_frame_mem (mode,
+ plus_constant (Pmode,
+ stack_pointer_rtx,
+ sp_offset + GET_MODE_SIZE (mode)));
+ rtx cfi_set2 = gen_rtx_SET (cfi_mem2, reg2);
+
+ /* The first part of a frame-related parallel insn is always
+ assumed to be relevant to the frame calculations;
+ subsequent parts, are only frame-related if
+ explicitly marked. */
if (aarch64_emit_cfi_for_reg_p (regno2))
- {
- const auto off = cfa_offset + GET_MODE_SIZE (mode);
- rtx cfa_mem2 = gen_frame_mem (mode,
- plus_constant (Pmode,
- cfa_base,
- off));
- add_reg_note (insn, REG_CFA_OFFSET,
- gen_rtx_SET (cfa_mem2, reg2));
- }
+ RTX_FRAME_RELATED_P (cfi_set2) = 1;
+
+ /* Add a REG_FRAME_RELATED_EXPR note since the unspec
+ representation of stp cannot be understood directly by
+ dwarf2cfi. */
+ rtx par = gen_rtx_PARALLEL (VOIDmode,
+ gen_rtvec (2, cfi_set, cfi_set2));
+ add_reg_note (insn, REG_FRAME_RELATED_EXPR, par);
regno = regno2;
++i;
}
- else if (mode == VNx2DImode && BYTES_BIG_ENDIAN)
- insn = emit_insn (gen_aarch64_pred_mov (mode, mem, ptrue, move_src));
- else if (aarch64_sve_mode_p (mode))
- insn = emit_insn (gen_rtx_SET (mem, move_src));
else
- insn = emit_move_insn (mem, move_src);
+ {
+ if (mode == VNx2DImode && BYTES_BIG_ENDIAN)
+ {
+ insn = emit_insn (gen_aarch64_pred_mov (mode, mem,
+ ptrue, move_src));
+ need_cfi_note_p = true;
+ }
+ else if (aarch64_sve_mode_p (mode))
+ insn = emit_insn (gen_rtx_SET (mem, move_src));
+ else
+ insn = emit_move_insn (mem, move_src);
+
+ if (frame_related_p && (need_cfi_note_p || move_src != reg))
+ add_reg_note (insn, REG_FRAME_RELATED_EXPR, cfi_set);
+ }
RTX_FRAME_RELATED_P (insn) = frame_related_p;
- if (frame_related_p)
- add_reg_note (insn, REG_CFA_OFFSET, gen_rtx_SET (cfa_mem, reg));
/* Emit a fake instruction to indicate that the VG save slot has
been initialized. */
diff --git a/gcc/testsuite/gcc.target/aarch64/pr113077.c b/gcc/testsuite/gcc.target/aarch64/pr113077.c
new file mode 100644
index 00000000000..dca202bd2ba
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/pr113077.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-O2 -fstack-protector-strong -fstack-clash-protection" } */
+void add_key(const void *payload);
+void act_keyctl_test(void) {
+ char buf[1030 * 1024];
+ int i = 0;
+ for (i = 0; i < sizeof(buf); i++)
+ {
+ add_key(buf);
+ }
+}
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