From e4b0531c526e7790c97c5de54859f2ad557e1e0c Mon Sep 17 00:00:00 2001
From: Dan Blackwell <dan_blackwell@apple.com>
Date: Wed, 10 Dec 2025 16:05:15 +0000
Subject: [PATCH] [AArch64] Make StackTagging use alloca getAllocationSize
 rather than lifetime size

This was causing zero sized setTags to be emitted when compiling with Swift with memtag-stack sanitization; this caused an assert in the backend 'N->getOpcode() != ISD::EntryToken && "EntryToken in CSEMap!"'.

This patch does as the title says and replaces the use of the lifetime size argument with AllocaInst.getAllocationSize.

rdar://164400893
---
 llvm/lib/Target/AArch64/AArch64StackTagging.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64StackTagging.cpp b/llvm/lib/Target/AArch64/AArch64StackTagging.cpp
index 75c7dd944b467..35a0aa0ef7df3 100644
--- a/llvm/lib/Target/AArch64/AArch64StackTagging.cpp
+++ b/llvm/lib/Target/AArch64/AArch64StackTagging.cpp
@@ -586,8 +586,7 @@ bool AArch64StackTagging::runOnFunction(Function &Fn) {
                                    ClMaxLifetimes);
     if (StandardLifetime) {
       IntrinsicInst *Start = Info.LifetimeStart[0];
-      uint64_t Size =
-          cast<ConstantInt>(Start->getArgOperand(0))->getZExtValue();
+      uint64_t Size = *Info.AI->getAllocationSize(*DL);
       Size = alignTo(Size, kTagGranuleSize);
       tagAlloca(AI, Start->getNextNode(), TagPCall, Size);