[WebAssembly] Strip TLS when "atomics" is not enabled

[sunfish]

Summary

With f3b4f99007cdcb3306484c9a39d31addc20aaa69, the exclusive source of truth for whether threads are supported is the -matomics flag. Accordingly, strip TLS flags when -matomic is not specified, even if bulk-memory is specified and it would theoretically be supportable. This allows the backend to compile TLS variables when -mbulk-memory is enabled but threads are not enabled.

[sbc100]

The addition of -mcpu seem seperate to the TLS issue.. maybe it can land separately? I wonder if we should rename or alias mvp to something more widely understandable such as v1 ?

llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

207–208

Why not else if here and avoid running stripThreadLocals twice?

[sbc100]

I think I've got a test case pending that actually needs this change.. can this be landed?

llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

bool runOnModule(Module &M) override {
     std::string FeatureStr = getFeatureString(Features);
     WasmTM->setTargetFeatureString(FeatureStr);
     for (auto &F : M)
       replaceFeatures(F, FeatureStr);
 
     bool StrippedAtomics = false;
     bool StrippedTLS = false;
 
-    if (!Features[WebAssembly::FeatureAtomics])
+    if (!Features[WebAssembly::FeatureAtomics]) {
       StrippedAtomics = stripAtomics(M);
-
-    if (!Features[WebAssembly::FeatureBulkMemory])
       StrippedTLS = stripThreadLocals(M);
+    } else if (!Features[WebAssembly::FeatureBulkMemory]) {
+      StrippedTLS |= stripThreadLocals(M);
+    }
 
     if (StrippedAtomics && !StrippedTLS)
       stripThreadLocals(M);
     else if (StrippedTLS && !StrippedAtomics)
       stripAtomics(M);
 
     recordFeatures(M, Features, StrippedAtomics || StrippedTLS);
 

llvm/test/CodeGen/WebAssembly/target-features-tls.ll

-; RUN: llc < %s -mattr=-bulk-memory | FileCheck %s --check-prefixes NO-BULK-MEM
-; RUN: llc < %s -mattr=+bulk-memory | FileCheck %s --check-prefixes BULK-MEM
+; RUN: llc < %s -mattr=-bulk-memory,atomics | FileCheck %s --check-prefixes NO-BULK-MEM
+; RUN: llc < %s -mattr=+bulk-memory,atomics | FileCheck %s --check-prefixes BULK-MEM
 
 ; Test that the target features section contains -atomics or +atomics
 ; for modules that have thread local storage in their source.
 
 target triple = "wasm32-unknown-unknown"
 
 @foo = internal thread_local global i32 0
 
 ; -bulk-memory
 ; NO-BULK-MEM-LABEL: .custom_section.target_features,"",@
-; NO-BULK-MEM-NEXT: .int8 1
+; NO-BULK-MEM-NEXT: .int8 2
+; NO-BULK-MEM-NEXT: .int8 43
+; NO-BULK-MEM-NEXT: .int8 7
+; NO-BULK-MEM-NEXT: .ascii "atomics"
 ; NO-BULK-MEM-NEXT: .int8 45
 ; NO-BULK-MEM-NEXT: .int8 10
 ; NO-BULK-MEM-NEXT: .ascii "shared-mem"
 ; NO-BULK-MEM-NEXT: .bss.foo,"",@
 
 ; +bulk-memory
 ; BULK-MEM-LABEL: .custom_section.target_features,"",@
-; BULK-MEM-NEXT: .int8 1
+; BULK-MEM-NEXT: .int8 2
+; BULK-MEM-NEXT: .int8 43
+; BULK-MEM-NEXT: .int8 7
+; BULK-MEM-NEXT: .ascii "atomics"
 ; BULK-MEM-NEXT: .int8 43
 ; BULK-MEM-NEXT: .int8 11
 ; BULK-MEM-NEXT: .ascii "bulk-memory"
 ; BULK-MEM-NEXT: .tbss.foo,"T",@

llvm/test/CodeGen/WebAssembly/tls-general-dynamic.ll

-; RUN: not --crash llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory 2>&1 | FileCheck %s --check-prefix=ERROR
-; RUN: not --crash llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory -fast-isel 2>&1 | FileCheck %s --check-prefix=ERROR
-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory --mtriple wasm32-unknown-emscripten | FileCheck %s --check-prefixes=CHECK,TLS
-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory --mtriple wasm32-unknown-emscripten -fast-isel | FileCheck %s --check-prefixes=CHECK,TLS
-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=-bulk-memory | FileCheck %s --check-prefixes=CHECK,NO-TLS
+; RUN: not --crash llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory,atomics 2>&1 | FileCheck %s --check-prefix=ERROR
+; RUN: not --crash llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory,atomics -fast-isel 2>&1 | FileCheck %s --check-prefix=ERROR
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory,atomics --mtriple wasm32-unknown-emscripten | FileCheck %s --check-prefixes=CHECK,TLS
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory,atomics --mtriple wasm32-unknown-emscripten -fast-isel | FileCheck %s --check-prefixes=CHECK,TLS
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=-bulk-memory,atomics | FileCheck %s --check-prefixes=CHECK,NO-TLS
 target triple = "wasm32-unknown-unknown"
 
 ; ERROR: LLVM ERROR: only -ftls-model=local-exec is supported for now on non-Emscripten OSes: variable tls
 
 ; CHECK-LABEL: address_of_tls:
 ; CHECK-NEXT: .functype  address_of_tls () -> (i32)
 define i32 @address_of_tls() {
   ; TLS-DAG: global.get __tls_base

llvm/test/CodeGen/WebAssembly/tls-local-exec.ll

-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory | FileCheck %s --check-prefixes=CHECK,TLS
-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory -fast-isel | FileCheck %s --check-prefixes=CHECK,TLS
-; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=-bulk-memory | FileCheck %s --check-prefixes=CHECK,NO-TLS
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory,atomics | FileCheck %s --check-prefixes=CHECK,TLS
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=+bulk-memory,atomics -fast-isel | FileCheck %s --check-prefixes=CHECK,TLS
+; RUN: llc < %s -asm-verbose=false -disable-wasm-fallthrough-return-opt -wasm-disable-explicit-locals -mattr=-bulk-memory,atomics | FileCheck %s --check-prefixes=CHECK,NO-TLS
 target triple = "wasm32-unknown-unknown"
 
 ; CHECK-LABEL: address_of_tls:
 ; CHECK-NEXT: .functype  address_of_tls () -> (i32)
 define i32 @address_of_tls() {
   ; TLS-DAG: global.get __tls_base
   ; TLS-DAG: i32.const tls@TLSREL
   ; TLS-NEXT: i32.add