From: David Malcolm <dmalcolm@redhat.com>
Date: Thu, 12 Mar 2026 00:45:29 +0000 (-0400)
Subject: analyzer: fix ICE on effective modulo by zero [PR124433]
X-Git-Tag: basepoints/gcc-17~786
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=54ee3bfa3bcea520728ada5654089f02fc508a1f;p=thirdparty%2Fgcc.git

analyzer: fix ICE on effective modulo by zero [PR124433]

gcc/analyzer/ChangeLog:
	PR analyzer/124433
	* region-model-manager.cc
	(region_model_manager::maybe_fold_binop): When checking for
	division by zero, use the value range of the divisor, rather
	than merely checking for constant 0.
	* region-model.cc (region_model::get_gassign_result): Likewise.

gcc/testsuite/ChangeLog:
	PR analyzer/124433
	* gcc.dg/analyzer/divide-by-zero-ice-pr124433.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>
---

diff --git a/gcc/analyzer/region-model-manager.cc b/gcc/analyzer/region-model-manager.cc
index 33d9a62937c..702a8ae7244 100644
--- a/gcc/analyzer/region-model-manager.cc
+++ b/gcc/analyzer/region-model-manager.cc
@@ -803,8 +803,12 @@ region_model_manager::maybe_fold_binop (tree type, enum tree_code op,
     case ROUND_MOD_EXPR:
     case RDIV_EXPR:
     case EXACT_DIV_EXPR:
-      if (cst1 && zerop (cst1))
-	return get_or_create_unknown_svalue (type);
+      {
+	value_range arg1_vr;
+	if (arg1->maybe_get_value_range (arg1_vr))
+	  if (arg1_vr.zero_p ())
+	    return get_or_create_unknown_svalue (type);
+      }
       break;
     }
 
diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index a85c6958838..a044aeb9700 100644
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -1365,8 +1365,9 @@ region_model::get_gassign_result (const gassign *assign,
 		|| op == RDIV_EXPR
 		|| op == EXACT_DIV_EXPR))
 	  {
-	    if (const tree rhs2_cst = rhs2_sval->maybe_get_constant ())
-	      if (zerop (rhs2_cst))
+	    value_range rhs_vr;
+	    if (rhs2_sval->maybe_get_value_range (rhs_vr))
+	      if (rhs_vr.zero_p ())
 		{
 		  /* Ideally we should issue a warning here;
 		     see PR analyzer/124217.  */
diff --git a/gcc/testsuite/gcc.dg/analyzer/divide-by-zero-ice-pr124433.c b/gcc/testsuite/gcc.dg/analyzer/divide-by-zero-ice-pr124433.c
new file mode 100644
index 00000000000..9b52ac8cc5b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/divide-by-zero-ice-pr124433.c
@@ -0,0 +1,9 @@
+unsigned m;
+int c;
+
+void
+foo()
+{
+  do c %= (5ull << 40) & m;
+  while (c);
+}