lower-bitint: Fix lowering of middle sized _BitInt operations which can throw [PR112770]
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Commit Message
Hi!
The middle kind _BitInt lowering is mostly done by casting the BITINT_TYPE
operands (if any) to a signed/unsigned integer type which has larger/equal
precision, using such integer type also for the lhs (if BITINT_TYPE) and
and adding a cast after the statement from that new lhs to the old
(BITINT_TYPE) lhs. Note, for middle kind this isn't done for GIMPLE_CALLs.
Most of the time that works nicely, the exception as the following testcase
shows is -fnon-call-exceptions and some operations which can trap. Because
inserting the cast to a new lhs after the statement results in a trapping
statement in the middle of a basic block.
The following patch fixes that by emitting the cast on the fallthru edge
instead.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2023-12-01 Jakub Jelinek <jakub@redhat.com>
PR middle-end/112770
* gimple-lower-bitint.cc (gimple_lower_bitint): When adjusting
lhs of middle _BitInt setter which ends bb, insert cast on
the fallthru edge rather than after stmt.
* gcc.dg/bitint-45.c: New test.
Jakub
Comments
On Fri, 1 Dec 2023, Jakub Jelinek wrote:
> Hi!
>
> The middle kind _BitInt lowering is mostly done by casting the BITINT_TYPE
> operands (if any) to a signed/unsigned integer type which has larger/equal
> precision, using such integer type also for the lhs (if BITINT_TYPE) and
> and adding a cast after the statement from that new lhs to the old
> (BITINT_TYPE) lhs. Note, for middle kind this isn't done for GIMPLE_CALLs.
> Most of the time that works nicely, the exception as the following testcase
> shows is -fnon-call-exceptions and some operations which can trap. Because
> inserting the cast to a new lhs after the statement results in a trapping
> statement in the middle of a basic block.
> The following patch fixes that by emitting the cast on the fallthru edge
> instead.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
> 2023-12-01 Jakub Jelinek <jakub@redhat.com>
>
> PR middle-end/112770
> * gimple-lower-bitint.cc (gimple_lower_bitint): When adjusting
> lhs of middle _BitInt setter which ends bb, insert cast on
> the fallthru edge rather than after stmt.
>
> * gcc.dg/bitint-45.c: New test.
>
> --- gcc/gimple-lower-bitint.cc.jj 2023-11-30 17:42:07.172487347 +0100
> +++ gcc/gimple-lower-bitint.cc 2023-11-30 19:04:08.004372919 +0100
> @@ -6336,7 +6336,13 @@ gimple_lower_bitint (void)
> type = build_nonstandard_integer_type (prec, uns);
> tree lhs2 = make_ssa_name (type);
> gimple *g = gimple_build_assign (lhs, NOP_EXPR, lhs2);
> - gsi_insert_after (&gsi, g, GSI_SAME_STMT);
> + if (stmt_ends_bb_p (stmt))
> + {
> + edge e = find_fallthru_edge (gsi_bb (gsi)->succs);
> + gsi_insert_on_edge_immediate (e, g);
> + }
> + else
> + gsi_insert_after (&gsi, g, GSI_SAME_STMT);
> gimple_set_lhs (stmt, lhs2);
> }
> unsigned int nops = gimple_num_ops (stmt);
> --- gcc/testsuite/gcc.dg/bitint-45.c.jj 2023-11-30 19:17:43.923888015 +0100
> +++ gcc/testsuite/gcc.dg/bitint-45.c 2023-11-30 19:17:35.502006495 +0100
> @@ -0,0 +1,11 @@
> +/* PR middle-end/112770 */
> +/* { dg-do compile { target bitint128 } } */
> +/* { dg-options "-std=c23 -fnon-call-exceptions" } */
> +
> +void
> +foo (void)
> +{
> + _BitInt(128) a = 0;
> + a /= 0; /* { dg-warning "division by zero" } */
> + &a;
> +}
>
> Jakub
>
>
@@ -6336,7 +6336,13 @@ gimple_lower_bitint (void)
type = build_nonstandard_integer_type (prec, uns);
tree lhs2 = make_ssa_name (type);
gimple *g = gimple_build_assign (lhs, NOP_EXPR, lhs2);
- gsi_insert_after (&gsi, g, GSI_SAME_STMT);
+ if (stmt_ends_bb_p (stmt))
+ {
+ edge e = find_fallthru_edge (gsi_bb (gsi)->succs);
+ gsi_insert_on_edge_immediate (e, g);
+ }
+ else
+ gsi_insert_after (&gsi, g, GSI_SAME_STMT);
gimple_set_lhs (stmt, lhs2);
}
unsigned int nops = gimple_num_ops (stmt);
@@ -0,0 +1,11 @@
+/* PR middle-end/112770 */
+/* { dg-do compile { target bitint128 } } */
+/* { dg-options "-std=c23 -fnon-call-exceptions" } */
+
+void
+foo (void)
+{
+ _BitInt(128) a = 0;
+ a /= 0; /* { dg-warning "division by zero" } */
+ &a;
+}