[llvm] [MTE] add option to disable UAS for memtag-stack (PR #96360)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: Florian Mayer (fmayer)

<details>
<summary>Changes</summary>

This makes it UAR-only. This can be useful for debugging.


---
Full diff: https://github.com/llvm/llvm-project/pull/96360.diff


1 Files Affected:

- (modified) llvm/lib/Target/AArch64/AArch64StackTagging.cpp (+6-1) 


``````````diff
diff --git a/llvm/lib/Target/AArch64/AArch64StackTagging.cpp b/llvm/lib/Target/AArch64/AArch64StackTagging.cpp
index a1ced770bfbbf..71bcefff5d46e 100644
--- a/llvm/lib/Target/AArch64/AArch64StackTagging.cpp
+++ b/llvm/lib/Target/AArch64/AArch64StackTagging.cpp
@@ -71,6 +71,11 @@ static cl::opt<bool>
                      cl::init(true),
                      cl::desc("Use Stack Safety analysis results"));
 
+static cl::opt<bool>
+    ClStackTaggingUAS("stack-tagging-use-after-scope", cl::Hidden,
+                     cl::init(true),
+                     cl::desc("detect use after scope within function"));
+
 static cl::opt<unsigned> ClScanLimit("stack-tagging-merge-init-scan-limit",
                                      cl::init(40), cl::Hidden);
 
@@ -607,7 +612,7 @@ bool AArch64StackTagging::runOnFunction(Function &Fn) {
         SInfo.UnrecognizedLifetimes.empty() &&
         memtag::isStandardLifetime(Info.LifetimeStart, Info.LifetimeEnd, DT, LI,
                                    ClMaxLifetimes);
-    if (StandardLifetime) {
+    if (ClStackTaggingUAS && StandardLifetime) {
       IntrinsicInst *Start = Info.LifetimeStart[0];
       uint64_t Size =
           cast<ConstantInt>(Start->getArgOperand(0))->getZExtValue();

``````````

</details>


https://github.com/llvm/llvm-project/pull/96360