analyzer: fix uninit false +ves reading from DECL_HARD_REGISTER [PR108968]

gcc/analyzer/ChangeLog:
	PR analyzer/108968
	* region-model.cc (region_model::get_rvalue_1): Handle VAR_DECLs
	with a DECL_HARD_REGISTER by returning UNKNOWN.

gcc/testsuite/ChangeLog:
	PR analyzer/108968
	* gcc.dg/analyzer/uninit-pr108968-register.c: New test.

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

diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
index 2187aec..bf07cec 100644 (file)
--- a/gcc/analyzer/region-model.cc
+++ b/gcc/analyzer/region-model.cc
@@ -2203,9 +2203,16 @@ region_model::get_rvalue_1 (path_var pv, region_model_context *ctxt) const
        return get_rvalue_for_bits (TREE_TYPE (expr), reg, bits, ctxt);
       }
 
-    case SSA_NAME:
     case VAR_DECL:
+      if (DECL_HARD_REGISTER (pv.m_tree))
+       {
+         /* If it has a hard register, it doesn't have a memory region
+            and can't be referred to as an lvalue.  */
+         return m_mgr->get_or_create_unknown_svalue (TREE_TYPE (pv.m_tree));
+       }
+      /* Fall through. */
     case PARM_DECL:
+    case SSA_NAME:
     case RESULT_DECL:
     case ARRAY_REF:
       {

diff --git a/gcc/testsuite/gcc.dg/analyzer/uninit-pr108968-register.c b/gcc/testsuite/gcc.dg/analyzer/uninit-pr108968-register.c
new file mode 100644 (file)
index 0000000..a76c09e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/analyzer/uninit-pr108968-register.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target x86_64-*-* } } */
+
+#define STACK_SIZE 4096
+struct cpu_info {};
+struct cpu_info *get_cpu_info(void)
+{
+  register unsigned long sp asm("rsp");
+  return (struct cpu_info *)((sp | (STACK_SIZE - 1)) + 1) - 1; /* { dg-bogus "use of uninitialized value 'sp'" } */
+}