[WebAssembly] Remove uses of ThreadModel

Summary:
In the clang UI, replaces -mthread-model posix with -matomics as the
source of truth on threading. In the backend, replaces
-thread-model=posix with the atomics target feature, which is now
collected on the WebAssemblyTargetMachine along with all other used
features. These collected features will also be used to emit the
target features section in the future.

The default configuration for the backend is thread-model=posix and no
atomics, which was previously an invalid configuration. This change
makes the default valid because the thread model is ignored.

A side effect of this change is that objects are never emitted with
passive segments. It will instead be up to the linker to decide
whether sections should be active or passive based on whether atomics
are used in the final link.

Reviewers: aheejin, sbc100, dschuff

Subscribers: mehdi_amini, jgravelle-google, hiraditya, sunfish, steven_wu, dexonsmith, rupprecht, jfb, jdoerfert, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D58742

llvm-svn: 355112

1 files changed, 4 insertions, 6 deletions

diff --git a/llvm/test/CodeGen/WebAssembly/global.ll b/llvm/test/CodeGen/WebAssembly/global.ll
index d341ebc8f36..12f4db43f38 100644
--- a/llvm/test/CodeGen/WebAssembly/global.ll
+++ b/llvm/test/CodeGen/WebAssembly/global.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -thread-model=single -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers | FileCheck %s --check-prefixes=CHECK,SINGLE
-; RUN: llc < %s -thread-model=posix -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers | FileCheck %s --check-prefixes=CHECK,THREADS
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=-atomics | FileCheck %s
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -wasm-keep-registers -mattr=+atomics | FileCheck %s
 
 ; Test that globals assemble as expected.
 
@@ -192,8 +192,7 @@ define i8* @call_memcpy(i8* %p, i8* nocapture readonly %q, i32 %n) {
 
 ; Constant global.
 ; CHECK: .type    rom,@object{{$}}
-; SINGLE: .section .rodata.rom,""
-; THREADS: .section .rodata.rom,"passive"
+; CHECK: .section .rodata.rom,""
 ; CHECK: .globl   rom{{$}}
 ; CHECK: .p2align   4{{$}}
 ; CHECK: rom:
@@ -206,8 +205,7 @@ define i8* @call_memcpy(i8* %p, i8* nocapture readonly %q, i32 %n) {
 ; CHECK-NEXT: .skip       8
 ; CHECK-NEXT: .size       array, 8
 ; CHECK: .type       pointer_to_array,@object
-; SINGLE-NEXT: .section    .rodata.pointer_to_array,""
-; THREADS-NEXT: .section    .rodata.pointer_to_array,"passive"
+; CHECK-NEXT: .section    .rodata.pointer_to_array,""
 ; CHECK-NEXT: .globl      pointer_to_array
 ; CHECK-NEXT: .p2align      2
 ; CHECK-NEXT: pointer_to_array: