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lower-bitint: Remove single label _BitInt switches [PR113737]

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The following testcase ICEs, because group_case_labels_stmt optimizes
  switch (a.0_7) <default: <L6> [50.00%], case 0: <L7> [50.00%], case 2: <L7> [50.00%]>
where L7 block starts with __builtin_unreachable (); to
  switch (a.0_7) <default: <L6> [50.00%]>
and single label GIMPLE_SWITCH is something the switch expansion refuses to
lower:
  if (gimple_switch_num_labels (m_switch) == 1
      || range_check_type (index_type) == NULL_TREE)
    return false;
(range_check_type never returns NULL for BITINT_TYPE), but the gimple
lowering pass relies on all large/huge _BitInt switches to be lowered
by that pass.

The following patch just removes those after making the single successor
edge EDGE_FALLTHRU.  I've done it even if !optimize just in case in case
we'd end up with single case label from earlier passes.

2024-02-05  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113737
	* gimple-lower-bitint.cc (gimple_lower_bitint): If GIMPLE_SWITCH
	has just a single label, remove it and make single successor edge
	EDGE_FALLTHRU.

	* gcc.dg/bitint-84.c: New test.
This commit is contained in:
Jakub Jelinek 2024-02-05 10:57:39 +01:00
parent d413df070b
commit dede174fbb
2 changed files with 40 additions and 1 deletions
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9
gcc/gimple-lower-bitint.cc
View file

@ -5832,7 +5832,14 @@ gimple_lower_bitint (void)
if (optimize)
group_case_labels_stmt (swtch);
switch_statements.safe_push (swtch);
if (gimple_switch_num_labels (swtch) == 1)
{
single_succ_edge (bb)->flags |= EDGE_FALLTHRU;
gimple_stmt_iterator gsi = gsi_for_stmt (swtch);
gsi_remove (&gsi, true);
}
else
switch_statements.safe_push (swtch);
}
}

32
gcc/testsuite/gcc.dg/bitint-84.c Normal file
View file

@ -0,0 +1,32 @@
/* PR tree-optimization/113737 */
/* { dg-do compile { target bitint } } */
/* { dg-options "-O2 -std=c23" } */
#if __BITINT_MAXWIDTH__ >= 129
_BitInt(129) a;
#else
_BitInt(63) a;
#endif
int b[1], c;
int
foo (void)
{
switch (a)
case 0:
case 2:
return 1;
return 0;
}
void
bar (int i)
{
for (;; ++i)
{
c = b[i];
if (!foo ())
__asm__ ("");
}
}