Fix a small regression impacting MSVC debug builds (#285)

* decomp: Fix nonempty_intersection impl for MSVC Debugging use-case

* docs: Add info on getting ASan builds running on Visual Studio w/o exceptions

README.md

@@ -12,11 +12,14 @@
 - [Table of Contents](#table-of-contents)
 - [Project Description](#project-description)
 - [Getting Started - Linux (Ubuntu)](#getting-started---linux-ubuntu)
+- [Getting Started - Linux (Arch)](#getting-started---linux-arch)
+- [Getting Started - Nixpkgs](#getting-started---nixpkgs)
 - [Getting Started - Windows](#getting-started---windows)
 - [Project Layout](#project-layout)
 - [Directory Layout](#directory-layout)
 - [More Documentation](#more-documentation)
 - [ASan Build](#asan-build)
+  - [On Windows / Visual Studio](#on-windows--visual-studio)
 <!-- tocstop -->
 ## Project Description
 
@@ -236,3 +239,8 @@ You will have to delete the build folder when changing compilers.  When running
 ```
 
 Then you can run the tests, runtime, and compiler as normal and they will abort if ASan finds an error.
+
+### On Windows / Visual Studio
+
+Until 16.9 Preview 4, when attaching a debugger to the ASan build, you must disable breaking on Win32 Access Violation exceptions.  See the relevant section `Debugging - Exceptions` here https://devblogs.microsoft.com/cppblog/asan-for-windows-x64-and-debug-build-support/#known-issues
+

decompiler/IR2/FormStack.cpp

@@ -110,10 +110,12 @@ Form* FormStack::pop_reg(const Variable& var,
 
 namespace {
 bool nonempty_intersection(const RegSet& a, const RegSet& b) {
-  // todo - if we ever switch to bit reg sets, this could be a lot faster.
-  std::vector<Register> isect;
-  std::set_intersection(a.begin(), a.end(), b.begin(), b.end(), std::back_inserter(isect));
-  return !isect.empty();
+  for (auto x : a) {
+    if (b.find(x) != b.end()) {
+      return true;
+    }
+  }
+  return false;
 }
 }  // namespace
 
@@ -378,4 +380,4 @@ std::vector<FormElement*> rewrite_to_get_var(FormStack& stack,
   return default_result;
 }
 
-}  // namespace decompiler
+}  // namespace decompiler