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| author | Jakub Jelinek <jakub@redhat.com> | 2024-02-15 15:53:01 +0100 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2024-02-15 15:53:01 +0100 |
| commit | 2b4efc5db2aedb59196987300e14951d08cd7106 (patch) | |
| tree | 3183042a21fa9e223eb09932ad4eb8d19c8511e1 /gcc/cfgrtl.h | |
| parent | b312cf21afd62b43fbc5034703e2796b0c3c416d (diff) | |
| download | gcc-2b4efc5db2aedb59196987300e14951d08cd7106.zip gcc-2b4efc5db2aedb59196987300e14951d08cd7106.tar.gz gcc-2b4efc5db2aedb59196987300e14951d08cd7106.tar.bz2 | |
expand: Fix handling of asm goto outputs vs. PHI argument adjustments [PR113921]
The Linux kernel and the following testcase distilled from it is
miscompiled, because tree-outof-ssa.cc (eliminate_phi) emits some
fixups on some of the edges (but doesn't commit edge insertions).
Later expand_asm_stmt emits further instructions on the same edge.
Now the problem is that expand_asm_stmt uses insert_insn_on_edge
to add its own fixups, but that function appends to the existing
sequence on the edge if any. And the bug triggers when the
fixup sequence emitted by eliminate_phi uses a pseudo which the
fixup sequence emitted by expand_asm_stmt later on sets.
So, we end up with
(set (reg A) (asm_operands ...))
and on one of the edges queued sequence
(set (reg C) (reg B)) // added by eliminate_phi
(set (reg B) (reg A)) // added by expand_asm_stmt
That is wrong, what we emit by expand_asm_stmt needs to be as close
to the asm_operands as possible (they aren't known until expand_asm_stmt
is called, the PHI fixup code assumes it is reg B which holds the right
value) and the PHI adjustments need to be done after it.
So, the following patch introduces a prepend_insn_to_edge function and
uses it from expand_asm_stmt, so that we queue
(set (reg B) (reg A)) // added by expand_asm_stmt
(set (reg C) (reg B)) // added by eliminate_phi
instead and so the value from the asm_operands output propagates correctly
to the PHI result.
2024-02-15 Jakub Jelinek <jakub@redhat.com>
PR middle-end/113921
* cfgrtl.h (prepend_insn_to_edge): New declaration.
* cfgrtl.cc (insert_insn_on_edge): Clarify behavior in function
comment.
(prepend_insn_to_edge): New function.
* cfgexpand.cc (expand_asm_stmt): Use prepend_insn_to_edge instead of
insert_insn_on_edge.
* gcc.target/i386/pr113921.c: New test.
Diffstat (limited to 'gcc/cfgrtl.h')
| -rw-r--r-- | gcc/cfgrtl.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/gcc/cfgrtl.h b/gcc/cfgrtl.h index e6062d4..657cd08 100644 --- a/gcc/cfgrtl.h +++ b/gcc/cfgrtl.h @@ -38,6 +38,7 @@ extern edge try_redirect_by_replacing_jump (edge, basic_block, bool); extern void emit_barrier_after_bb (basic_block bb); extern basic_block force_nonfallthru_and_redirect (edge, basic_block, rtx); extern void insert_insn_on_edge (rtx, edge); +extern void prepend_insn_to_edge (rtx, edge); extern void commit_one_edge_insertion (edge e); extern void commit_edge_insertions (void); extern void print_rtl_with_bb (FILE *, const rtx_insn *, dump_flags_t); |