From b083203f053f1666e9cc1ded2abdf4e1688d1ec0 Mon Sep 17 00:00:00 2001
From: Richard Biener <rguenther@suse.de>
Date: Tue, 4 Jul 2023 10:29:26 +0200
Subject: [PATCH] tree-optimization/110228 - avoid undefs in ifcombine more
thoroughly
The following replaces the simplistic gimple_uses_undefined_value_p
with the conservative mark_ssa_maybe_undefs approach as already
used by LIM and IVOPTs. This is to avoid exposing an unconditional
uninitialized read on a path from entry by if-combine.
PR tree-optimization/110228
* tree-ssa-ifcombine.cc (pass_tree_ifcombine::execute):
Mark SSA may-undefs.
(bb_no_side_effects_p): Check stmt uses for undefs.
* gcc.dg/torture/pr110228.c: New testcase.
* gcc.dg/uninit-pr101912.c: Un-XFAIL.
---
gcc/testsuite/gcc.dg/torture/pr110228.c | 34 +++++++++++++++++++++++++
gcc/testsuite/gcc.dg/uninit-pr101912.c | 2 +-
gcc/tree-ssa-ifcombine.cc | 8 +++++-
3 files changed, 42 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr110228.c
diff --git a/gcc/testsuite/gcc.dg/torture/pr110228.c b/gcc/testsuite/gcc.dg/torture/pr110228.c
new file mode 100644
index 000000000000..add9f17b4219
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr110228.c
@@ -0,0 +1,34 @@
+/* { dg-do run { target x86_64-*-* i?86-*-* } } */
+/* { dg-require-effective-target lp64 } */
+
+unsigned a[4] = {1,1,1,1};
+unsigned tt1 = 0;
+
+__attribute__((noipa))
+static void bug(unsigned * p, unsigned *t, int n, int t2)
+{
+ for(int i = 0; i < n; i++)
+ {
+ _Bool LookupFlags ;
+ unsigned v = t[i];
+ unsigned tt = tt1;
+ if (v == 0)
+ LookupFlags = 0;
+ else if (v == 1)
+ LookupFlags = 1;
+ if (LookupFlags) {
+ tt|=3u;
+ LookupFlags = 0;
+ }
+ asm("movq $-1, %q1":"+a"(LookupFlags));
+ *p = tt;
+ }
+}
+
+int main()
+{
+ unsigned r = 42;
+ bug(&r,a, sizeof(a)/sizeof(a[0]), 1);
+ __builtin_printf("%u\n", r);
+ if (r != 3) __builtin_abort();
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-pr101912.c b/gcc/testsuite/gcc.dg/uninit-pr101912.c
index 62cd2a0c73e1..cb7d7516e91e 100644
--- a/gcc/testsuite/gcc.dg/uninit-pr101912.c
+++ b/gcc/testsuite/gcc.dg/uninit-pr101912.c
@@ -11,7 +11,7 @@ tzloadbody (void)
for (int i = 0; i < n; i++)
{
int corr = getint ();
- if (corr < 1 || (corr == 1 && !(leapcnt == 0 || (prevcorr < corr ? corr == prevcorr + 1 : (corr == prevcorr || corr == prevcorr - 1))))) /* { dg-bogus "uninitialized" "pr101912" { xfail *-*-* } } */
+ if (corr < 1 || (corr == 1 && !(leapcnt == 0 || (prevcorr < corr ? corr == prevcorr + 1 : (corr == prevcorr || corr == prevcorr - 1))))) /* { dg-bogus "uninitialized" "pr101912" } */
return -1;
prevcorr = corr;
diff --git a/gcc/tree-ssa-ifcombine.cc b/gcc/tree-ssa-ifcombine.cc
index 21a77ddecc7b..58e19c1508e4 100644
--- a/gcc/tree-ssa-ifcombine.cc
+++ b/gcc/tree-ssa-ifcombine.cc
@@ -128,7 +128,6 @@ bb_no_side_effects_p (basic_block bb)
gassign *ass;
enum tree_code rhs_code;
if (gimple_has_side_effects (stmt)
- || gimple_uses_undefined_value_p (stmt)
|| gimple_could_trap_p (stmt)
|| gimple_vuse (stmt)
/* We need to rewrite stmts with undefined overflow to use
@@ -153,6 +152,12 @@ bb_no_side_effects_p (basic_block bb)
should handle this. */
|| is_gimple_call (stmt))
return false;
+
+ ssa_op_iter it;
+ tree use;
+ FOR_EACH_SSA_TREE_OPERAND (use, stmt, it, SSA_OP_USE)
+ if (ssa_name_maybe_undef_p (use))
+ return false;
}
return true;
@@ -836,6 +841,7 @@ pass_tree_ifcombine::execute (function *fun)
bbs = single_pred_before_succ_order ();
calculate_dominance_info (CDI_DOMINATORS);
+ mark_ssa_maybe_undefs ();
/* Search every basic block for COND_EXPR we may be able to optimize.
--
GitLab