diff options
author | Jakub Jelinek <jakub@redhat.com> | 2024-02-15 15:53:01 +0100 |
---|---|---|
committer | Jakub Jelinek <jakub@redhat.com> | 2024-02-15 16:20:00 +0100 |
commit | 7a6e9e70ea88061981c5565c043985d8cde9ecc8 (patch) | |
tree | 32a2d4d64c5471370495eef5c6290a765dd9e502 | |
parent | 38466c71374d1ca7b79c7ef4793d4c14480fe8c4 (diff) |
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.c (insert_insn_on_edge): Clarify behavior in function
comment.
(prepend_insn_to_edge): New function.
* cfgexpand.c (expand_asm_stmt): Use prepend_insn_to_edge instead of
insert_insn_on_edge.
* gcc.target/i386/pr113921.c: New test.
(cherry picked from commit 2b4efc5db2aedb59196987300e14951d08cd7106)
-rw-r--r-- | gcc/cfgexpand.c | 2 | ||||
-rw-r--r-- | gcc/cfgrtl.c | 24 | ||||
-rw-r--r-- | gcc/cfgrtl.h | 1 | ||||
-rw-r--r-- | gcc/testsuite/gcc.target/i386/pr113921.c | 20 |
4 files changed, 44 insertions, 3 deletions
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c index a607ad50d2b..d3768a6134b 100644 --- a/gcc/cfgexpand.c +++ b/gcc/cfgexpand.c @@ -3639,7 +3639,7 @@ expand_asm_stmt (gasm *stmt) emit_insn (copy_insn (PATTERN (curr))); rtx_insn *copy = get_insns (); end_sequence (); - insert_insn_on_edge (copy, e); + prepend_insn_to_edge (copy, e); } } } diff --git a/gcc/cfgrtl.c b/gcc/cfgrtl.c index 4fb145ee4c4..e24c6c04ec8 100644 --- a/gcc/cfgrtl.c +++ b/gcc/cfgrtl.c @@ -25,7 +25,7 @@ along with GCC; see the file COPYING3. If not see - CFG-aware instruction chain manipulation delete_insn, delete_insn_chain - Edge splitting and committing to edges - insert_insn_on_edge, commit_edge_insertions + insert_insn_on_edge, prepend_insn_to_edge, commit_edge_insertions - CFG updating after insn simplification purge_dead_edges, purge_all_dead_edges - CFG fixing after coarse manipulation @@ -1990,7 +1990,8 @@ rtl_split_edge (edge edge_in) /* Queue instructions for insertion on an edge between two basic blocks. The new instructions and basic blocks (if any) will not appear in the - CFG until commit_edge_insertions is called. */ + CFG until commit_edge_insertions is called. If there are already + queued instructions on the edge, PATTERN is appended to them. */ void insert_insn_on_edge (rtx pattern, edge e) @@ -2010,6 +2011,25 @@ insert_insn_on_edge (rtx pattern, edge e) end_sequence (); } +/* Like insert_insn_on_edge, but if there are already queued instructions + on the edge, PATTERN is prepended to them. */ + +void +prepend_insn_to_edge (rtx pattern, edge e) +{ + /* We cannot insert instructions on an abnormal critical edge. + It will be easier to find the culprit if we die now. */ + gcc_assert (!((e->flags & EDGE_ABNORMAL) && EDGE_CRITICAL_P (e))); + + start_sequence (); + + emit_insn (pattern); + emit_insn (e->insns.r); + + e->insns.r = get_insns (); + end_sequence (); +} + /* Update the CFG for the instructions queued on edge E. */ void diff --git a/gcc/cfgrtl.h b/gcc/cfgrtl.h index 0c8568ba757..9ef8db33e23 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); diff --git a/gcc/testsuite/gcc.target/i386/pr113921.c b/gcc/testsuite/gcc.target/i386/pr113921.c new file mode 100644 index 00000000000..f7efba74143 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr113921.c @@ -0,0 +1,20 @@ +/* PR middle-end/113921 */ +/* { dg-do run } */ +/* { dg-options "-O2" } */ + +__attribute__((noipa)) long +foo (void) +{ + long v; + asm volatile goto ("jmp %l2" : "=r" (v) : "0" (27) : : lab); + return v; +lab: + return 42; +} + +int +main () +{ + if (foo () != 42) + __builtin_abort (); +} |