File llvm-fix-unordered-stores-when-lowering-to-cmpxchg.patch of Package llvm7.17608

From 2153c4b8281c1e5f25887ef9183947198c50a9d2 Mon Sep 17 00:00:00 2001
From: Philip Reames <listmail@philipreames.com>
Date: Tue, 19 Mar 2019 17:20:49 +0000
Subject: [PATCH] [AtomicExpand] Fix a crash bug when lowering unordered loads
 to cmpxchg

Add tests for wider atomic loads and stores.  In the process, fix a crasher where we appearently handled unorder stores, but not loads, when lowering to cmpxchg idioms.

llvm-svn: 356482

---
 lib/CodeGen/AtomicExpandPass.cpp     |   3 +
 test/CodeGen/X86/atomic-unordered.ll | 234 +++++++++++++++++++---
 2 files changed, 213 insertions(+), 24 deletions(-)

---
NOTE (Sirringhaus): Test file does not exist yet, only take the fix.

diff --git a/lib/CodeGen/AtomicExpandPass.cpp b/lib/CodeGen/AtomicExpandPass.cpp
index 10dd21d1ef9d..7a8013abccfb 100644
--- a/lib/CodeGen/AtomicExpandPass.cpp
+++ b/lib/CodeGen/AtomicExpandPass.cpp
@@ -430,6 +430,9 @@ bool AtomicExpand::expandAtomicLoadToLL(LoadInst *LI) {
 bool AtomicExpand::expandAtomicLoadToCmpXchg(LoadInst *LI) {
   IRBuilder<> Builder(LI);
   AtomicOrdering Order = LI->getOrdering();
+  if (Order == AtomicOrdering::Unordered)
+    Order = AtomicOrdering::Monotonic;
+
   Value *Addr = LI->getPointerOperand();
   Type *Ty = cast<PointerType>(Addr->getType())->getElementType();
   Constant *DummyVal = Constant::getNullValue(Ty);