[compiler-rt] [nfc][tsan] Simplify morder conversion (PR #115075)

[Vitaly Buka via llvm-commits]

https://github.com/vitalybuka created https://github.com/llvm/llvm-project/pull/115075

All valid values should fit into a byte.
This slightly reduce generated code on x86_64.


>From e82a4cf5ac4f24f121dfc31028edfda5b3b31531 Mon Sep 17 00:00:00 2001
From: Vitaly Buka <vitalybuka at google.com>
Date: Tue, 5 Nov 2024 13:49:32 -0800
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
---
 compiler-rt/lib/tsan/rtl/tsan_interface_atomic.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/compiler-rt/lib/tsan/rtl/tsan_interface_atomic.cpp b/compiler-rt/lib/tsan/rtl/tsan_interface_atomic.cpp
index d12e0f596a7fb4..dd37e86ebd7583 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interface_atomic.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interface_atomic.cpp
@@ -515,7 +515,9 @@ static morder to_morder(int mo) {
   // since we use __sync_ atomics for actual atomic operations,
   // we can safely ignore it as well. It also subtly affects semantics,
   // but we don't model the difference.
-  return static_cast<morder>(mo & 0x7fff);
+  morder res = static_cast<morder>(static_cast<u8>(mo));
+  DCHECK_LE(res, mo_seq_cst);
+  return res;
 }
 
 #  define ATOMIC_IMPL(func, mo, ...)                                  \