[WebAssembly] Add target feature for atomics

Summary:
This tracks the WebAssembly threads feature proposal at
https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md

Differential Revision: https://reviews.llvm.org/D37300

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312145 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/test/CodeGen/WebAssembly/atomics.ll b/test/CodeGen/WebAssembly/atomics.ll
new file mode 100644
index 00000000000..1845187f505
--- /dev/null
+++ b/test/CodeGen/WebAssembly/atomics.ll
@@ -0,0 +1,19 @@
+; RUN: not llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt 
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -mattr=+atomics | FileCheck %s
+
+; Test that atomic loads are assembled properly.
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown-wasm"
+
+; CHECK-LABEL: load_i32_atomic:
+; CHECK-NEXT: .param i32{{$}}
+; CHECK-NEXT: .result i32{{$}}
+; CHECK-NEXT: get_local $push[[L0:[0-9]+]]=, 0{{$}}
+; CHECK-NEXT: i32.atomic.load $push[[NUM:[0-9]+]]=, 0($pop[[L0]]){{$}}
+; CHECK-NEXT: return $pop[[NUM]]{{$}}
+
+define i32 @load_i32_atomic(i32 *%p) {
+  %v = load atomic i32, i32* %p seq_cst, align 4
+  ret i32 %v
+}