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

[Florian Mayer via llvm-commits]

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

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


>From 5bc6b130856f8017e041e8e830c01e008de18d99 Mon Sep 17 00:00:00 2001
From: Florian Mayer <fmayer at google.com>
Date: Fri, 21 Jun 2024 14:26:45 -0700
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.4
---
 llvm/lib/Target/AArch64/AArch64StackTagging.cpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

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();