[gcc r14-12792] gimplify: Allow declarations in recalculate_side_effects [PR126497]

https://gcc.gnu.org/g:bbe1892f92c5b76637a53c376e6ff7f8095ca851

commit r14-12792-gbbe1892f92c5b76637a53c376e6ff7f8095ca851
Author: Jakub Jelinek <[email protected]>
Date:   Fri Jul 31 09:05:50 2026 +0200

    gimplify: Allow declarations in recalculate_side_effects [PR126497]
    
    The following testcase ICEs, because we decide to fold a comparison
    into just one of its operands, we call recalculate_side_effects on that
    and ICE on the assertion that it isn't called on anything unexpected
    (here PARM_DECL).
    Already some time ago we had to add an exception for SSA_NAME for the
    same reason.
    The tcc_declaration case is slightly different, TREE_SIDE_EFFECTS is
    sometimes present on those if they are TREE_THIS_VOLATILE, but it is
    something the FE should take care of when creating those decls, not
    a business of the gimplifier.
    
    2026-07-31  Jakub Jelinek  <[email protected]>
    
            PR middle-end/126497
            * gimplify.cc (recalculate_side_effects): Return for
            tcc_declaration.
    
            * gcc.dg/bitint-141.c: New test.
    
    Reviewed-by: Andrea Pinski <[email protected]>
    (cherry picked from commit ca867fd9d5ace4ede8289dba9ae731e554bde618)

Diff:
---
 gcc/gimplify.cc                   |  7 +++++++
 gcc/testsuite/gcc.dg/bitint-141.c | 19 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/gcc/gimplify.cc b/gcc/gimplify.cc
index 7fdfbe25a8ae..6cc2d1299f04 100644
--- a/gcc/gimplify.cc
+++ b/gcc/gimplify.cc
@@ -3372,6 +3372,13 @@ recalculate_side_effects (tree t)
       /* No side-effects.  */
       return;
 
+    case tcc_declaration:
+      /* These can have side-effects if TREE_THIS_VOLATILE,
+	 but those should be set elsewhere, not in
+	 recalculate_side_effects.  Can be triggered e.g. if
+	 a comparison is folded into one of its operands.  */
+      return;
+
     default:
       if (code == SSA_NAME)
 	/* No side-effects.  */
diff --git a/gcc/testsuite/gcc.dg/bitint-141.c b/gcc/testsuite/gcc.dg/bitint-141.c
new file mode 100644
index 000000000000..f3f22bbb0bf3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/bitint-141.c
@@ -0,0 +1,19 @@
+/* PR middle-end/126497 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-std=c23" } */
+
+typedef unsigned _BitInt (1) U;
+
+U
+foo (U a)
+{
+  U t = a >= 1uwb;
+  return t;
+}
+
+U
+bar (U a)
+{
+  U t = a == 1uwb;
+  return t;
+}