From 6c152c9db3b5b9d43e12846fb7a44977c0b65fc2 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 18 Apr 2024 09:45:14 +0200
Subject: [PATCH] internal-fn: Temporarily disable flag_trapv during
.{ADD,SUB,MUL}_OVERFLOW etc. expansion [PR114753]
__builtin_{add,sub,mul}_overflow{,_p} builtins are well defined
for all inputs even for -ftrapv, and the -fsanitize=signed-integer-overflow
ifns shouldn't abort in libgcc but emit the desired ubsan diagnostics
or abort depending on -fsanitize* setting regardless of -ftrapv.
The expansion of these internal functions uses expand_expr* in various
places (e.g. MULT_EXPR at least in 2 spots), so temporarily disabling
flag_trapv in all those spots would be hard.
The following patch disables it around the bodies of 3 functions
which can do the expand_expr calls.
If it was in the C++ FE, I'd use some RAII sentinel, but I don't think
we have one in the middle-end.
2024-04-18 Jakub Jelinek <jakub@redhat.com>
PR middle-end/114753
* internal-fn.cc (expand_mul_overflow): Save flag_trapv and
temporarily clear it for the duration of the function, then
restore previous value.
(expand_vector_ubsan_overflow): Likewise.
(expand_arith_overflow): Likewise.
* gcc.dg/pr114753.c: New test.
---
gcc/internal-fn.cc | 18 ++++++++++++++++++
gcc/testsuite/gcc.dg/pr114753.c | 14 ++++++++++++++
2 files changed, 32 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/pr114753.c
diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
index 5269f0ac528e..c7c5222a169c 100644
--- a/gcc/internal-fn.cc
+++ b/gcc/internal-fn.cc
@@ -1631,7 +1631,11 @@ expand_mul_overflow (location_t loc, tree lhs, tree arg0, tree arg1,
rtx target = NULL_RTX;
signop sign;
enum insn_code icode;
+ int save_flag_trapv = flag_trapv;
+ /* We don't want any __mulv?i3 etc. calls from the expansion of
+ these internal functions, so disable -ftrapv temporarily. */
+ flag_trapv = 0;
done_label = gen_label_rtx ();
do_error = gen_label_rtx ();
@@ -2479,6 +2483,7 @@ expand_mul_overflow (location_t loc, tree lhs, tree arg0, tree arg1,
else
expand_arith_overflow_result_store (lhs, target, mode, res);
}
+ flag_trapv = save_flag_trapv;
}
/* Expand UBSAN_CHECK_* internal function if it has vector operands. */
@@ -2499,7 +2504,11 @@ expand_vector_ubsan_overflow (location_t loc, enum tree_code code, tree lhs,
rtx resvr = NULL_RTX;
unsigned HOST_WIDE_INT const_cnt = 0;
bool use_loop_p = (!cnt.is_constant (&const_cnt) || const_cnt > 4);
+ int save_flag_trapv = flag_trapv;
+ /* We don't want any __mulv?i3 etc. calls from the expansion of
+ these internal functions, so disable -ftrapv temporarily. */
+ flag_trapv = 0;
if (lhs)
{
optab op;
@@ -2629,6 +2638,7 @@ expand_vector_ubsan_overflow (location_t loc, enum tree_code code, tree lhs,
}
else if (resvr)
emit_move_insn (lhsr, resvr);
+ flag_trapv = save_flag_trapv;
}
/* Expand UBSAN_CHECK_ADD call STMT. */
@@ -2707,7 +2717,11 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
prec0 = MIN (prec0, pr);
pr = get_min_precision (arg1, uns1_p ? UNSIGNED : SIGNED);
prec1 = MIN (prec1, pr);
+ int save_flag_trapv = flag_trapv;
+ /* We don't want any __mulv?i3 etc. calls from the expansion of
+ these internal functions, so disable -ftrapv temporarily. */
+ flag_trapv = 0;
/* If uns0_p && uns1_p, precop is minimum needed precision
of unsigned type to hold the exact result, otherwise
precop is minimum needed precision of signed type to
@@ -2748,6 +2762,7 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
ops.location = loc;
rtx tem = expand_expr_real_2 (&ops, NULL_RTX, mode, EXPAND_NORMAL);
expand_arith_overflow_result_store (lhs, target, mode, tem);
+ flag_trapv = save_flag_trapv;
return;
}
@@ -2771,6 +2786,7 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
if (integer_zerop (arg0) && !unsr_p)
{
expand_neg_overflow (loc, lhs, arg1, false, NULL);
+ flag_trapv = save_flag_trapv;
return;
}
/* FALLTHRU */
@@ -2781,6 +2797,7 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
case MULT_EXPR:
expand_mul_overflow (loc, lhs, arg0, arg1, unsr_p,
unsr_p, unsr_p, false, NULL);
+ flag_trapv = save_flag_trapv;
return;
default:
gcc_unreachable ();
@@ -2826,6 +2843,7 @@ expand_arith_overflow (enum tree_code code, gimple *stmt)
else
expand_mul_overflow (loc, lhs, arg0, arg1, unsr_p,
uns0_p, uns1_p, false, NULL);
+ flag_trapv = save_flag_trapv;
return;
}
diff --git a/gcc/testsuite/gcc.dg/pr114753.c b/gcc/testsuite/gcc.dg/pr114753.c
new file mode 100644
index 000000000000..117f2c36d3ef
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr114753.c
@@ -0,0 +1,14 @@
+/* PR middle-end/114753 */
+/* { dg-do run } */
+/* { dg-options "-O2 -ftrapv" } */
+
+int
+main ()
+{
+ volatile long long i = __LONG_LONG_MAX__;
+ volatile long long j = 2;
+ long long k;
+ if (!__builtin_mul_overflow (i, j, &k) || k != -2LL)
+ __builtin_abort ();
+ return 0;
+}
--
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