re PR middle-end/70526 (GCC 6 miscompiles Firefox JIT compiler)

2016-04-05  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/70526
	* tree-sra.c (build_ref_for_offset): Use prev_base to
	extract the alias pointer type.

	* g++.dg/torture/pr70526.C: New testcase.

From-SVN: r234749

gcc/ChangeLog

 2016-04-05  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/70526
+	* tree-sra.c (build_ref_for_offset): Use prev_base to
+	extract the alias pointer type.
+
+2016-04-05  Richard Biener  <rguenther@suse.de>
+
 	* dse.c (struct store_info): Remove alias_set member.
 	(struct read_info_type): Likewise.
 	(clear_alias_group, clear_alias_mode_table, clear_alias_mode_holder,

gcc/testsuite/ChangeLog

+2016-04-05  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/70526
+	* g++.dg/torture/pr70526.C: New testcase.
+
 2016-04-05  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/70525

gcc/testsuite/g++.dg/torture/pr70526.C

+// { dg-do run }
+
+typedef unsigned uint32_t;
+
+template<typename T>
+struct AlignedStorage2
+{
+  char mBytes[sizeof(T)];
+
+  const T* addr() const { return reinterpret_cast<const T*>(mBytes); }
+  T* addr() { return reinterpret_cast<T*>(mBytes); }
+};
+
+struct Register {
+    uint32_t reg_;
+};
+
+class TypedOrValueRegister
+{
+  AlignedStorage2<Register> typed;
+  __attribute__((noinline)) Register& dataTyped() { return *typed.addr(); }
+public:
+  TypedOrValueRegister(Register reg)
+    {
+      dataTyped() = reg;
+    }
+  Register typedReg() const { return *typed.addr(); }
+};
+
+int main() {
+    Register reg = { 10u };
+    if (TypedOrValueRegister(reg).typedReg().reg_ != 10)
+      __builtin_abort();
+    return 0;
+}

gcc/tree-sra.c

@@ -1673,7 +1673,7 @@ build_ref_for_offset (location_t loc, tree base, HOST_WIDE_INT offset,
     }
   else
     {
-      off = build_int_cst (reference_alias_ptr_type (base),
+      off = build_int_cst (reference_alias_ptr_type (prev_base),
 			   base_offset + offset / BITS_PER_UNIT);
       base = build_fold_addr_expr (unshare_expr (base));
     }