[llvm] [asan] Disable instrumentation for available_externally global with COFF (PR #81109)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Wu Yingcong (yingcong-wu)

<details>
<summary>Changes</summary>

For COFF, available_externally global will be instrumented because of the lack of filtering, and will trigger the Verifier pass assertion and crash the compilation. This patch will filter out the available_externally global for COFF.

For non-COFF, `!G->hasExactDefinition()` in line 1954 will filter out the available_externally globals.

There is a related bug reported in https://www.mail-archive.com/llvm-bugs@<!-- -->lists.llvm.org/msg46110.html. I tried the reproducer posted on the page and this will fix the problem.

---
Full diff: https://github.com/llvm/llvm-project/pull/81109.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp (+4) 
- (added) llvm/test/Instrumentation/AddressSanitizer/do-not-instrument-globals-windows.ll (+10) 


``````````diff
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index d4f5bf8c39356..80643e5b04860 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -1957,6 +1957,10 @@ bool ModuleAddressSanitizer::shouldInstrumentGlobal(GlobalVariable *G) const {
     // On COFF, don't instrument non-ODR linkages.
     if (G->isInterposable())
       return false;
+    // If the global has AvailableExternally linkage, then it is not in this 
+    // module, which means it does not need to be instrumented.
+    if (G->hasAvailableExternallyLinkage())
+      return false;
   }
 
   // If a comdat is present, it must have a selection kind that implies ODR
diff --git a/llvm/test/Instrumentation/AddressSanitizer/do-not-instrument-globals-windows.ll b/llvm/test/Instrumentation/AddressSanitizer/do-not-instrument-globals-windows.ll
new file mode 100644
index 0000000000000..c143f69f126a8
--- /dev/null
+++ b/llvm/test/Instrumentation/AddressSanitizer/do-not-instrument-globals-windows.ll
@@ -0,0 +1,10 @@
+; This test checks that we are not instrumenting unnecessary globals
+; RUN: opt < %s -passes=asan -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+ at v_available_externally = available_externally global i32 zeroinitializer
+; CHECK-NOT: {{asan_gen.*v_available_externally}}
+
+; CHECK: @asan.module_ctor

``````````

</details>


https://github.com/llvm/llvm-project/pull/81109