From e7ebb87222e33936f6e5f3bd3fda919080ece1a0 Mon Sep 17 00:00:00 2001
From: Philip Reames <listmail@philipreames.com>
Date: Thu, 25 Mar 2021 14:47:31 -0700
Subject: [deref] Handle byval/byref/sret/inalloc/preallocated arguments for
 deref-at-point semantics

All of these are scoped allocations which remain dereferenceable during the lifetime of the callee.

Differential Revision: https://reviews.llvm.org/D99310
---
 llvm/lib/IR/Value.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

(limited to 'llvm/lib/IR/Value.cpp')

diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index 8c06d4f..fb4eb9a 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -739,6 +739,12 @@ static bool canBeFreed(const Value *V) {
   if (isa<Constant>(V))
     return false;
 
+  // Handle byval/byref/sret/inalloca/preallocated arguments.  The storage
+  // lifetime is guaranteed to be longer than the callee's lifetime.
+  if (auto *A = dyn_cast<Argument>(V))
+    if (A->hasPointeeInMemoryValueAttr())
+      return false;
+
   const Function *F = nullptr;
   if (auto *I = dyn_cast<Instruction>(V))
     F = I->getFunction();
-- 
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