In simple_dce_from_worklist, we were removing an inline-asm which had a vdef (due to clobbering memory) but not unlinking the statement's vdef. This fixes that oversight. This was a latent bug exposed recently by both VRP and removal of stores to static starting to use simple_dce_from_worklist.
OK for trunk (and for GCC 12 after a week)? Bootstrapped and tested on x86_64-linux-gnu with no regressions. PR tree-optimization/108684 gcc/ChangeLog: * tree-ssa-dce.cc (simple_dce_from_worklist): Call unlink_stmt_vdef on the statement before removing it. gcc/testsuite/ChangeLog: * gcc.c-torture/compile/dce-inline-asm-1.c: New test. * gcc.c-torture/compile/dce-inline-asm-2.c: New test. co-authored-by: Andrew Macleod <amacl...@redhat.com> --- .../gcc.c-torture/compile/dce-inline-asm-1.c | 15 +++++++++++++++ .../gcc.c-torture/compile/dce-inline-asm-2.c | 16 ++++++++++++++++ gcc/tree-ssa-dce.cc | 1 + 3 files changed, 32 insertions(+) create mode 100644 gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c create mode 100644 gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c diff --git a/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c new file mode 100644 index 00000000000..a9f02e44bd7 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-1.c @@ -0,0 +1,15 @@ +/* PR tree-optimization/108684 */ +/* This used to ICE as when we remove the store to + `t`, we also would remove the inline-asm which + had a VDEF on it but we didn't update the + VUSE that was later on. */ +static int t; + +int f (int *a) +{ + int t1; + asm (" " : "=X" (t1) : : "memory"); + t = t1; + return *a; +} + diff --git a/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c new file mode 100644 index 00000000000..a41b16e4bd0 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/compile/dce-inline-asm-2.c @@ -0,0 +1,16 @@ +/* PR tree-optimization/108684 */ +/* This used to ICE as when we removed the + __builtin_unreachable in VRP, as we + would also remove the branch and the + inline-asm. The inline-asm had a VDEF on it, + which we didn't update further along and + not have the VDEF on the return statement + updated. */ + +int f (int a) +{ + asm (" " : "=X" (a) : : "memory"); + if (a) + return 0; + __builtin_unreachable(); +} diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc index b2fe9f4f55e..752785541e4 100644 --- a/gcc/tree-ssa-dce.cc +++ b/gcc/tree-ssa-dce.cc @@ -2140,6 +2140,7 @@ simple_dce_from_worklist (bitmap worklist) remove_phi_node (&gsi, true); else { + unlink_stmt_vdef (t); gsi_remove (&gsi, true); release_defs (t); } -- 2.31.1