[WebAssembly] Compute and export TLS block alignment

Summary:
Add immutable WASM global `__tls_align` which stores the alignment
requirements of the TLS segment.

Add `__builtin_wasm_tls_align()` intrinsic to get this alignment in Clang.

The expected usage has now changed to:

    __wasm_init_tls(memalign(__builtin_wasm_tls_align(),
                             __builtin_wasm_tls_size()));

Reviewers: tlively, aheejin, sbc100, sunfish, alexcrichton

Reviewed By: tlively

Subscribers: dschuff, jgravelle-google, hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D65028

llvm-svn: 366624

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
index 288b991ae2c..d9089deaa7b 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyMCInstLower.cpp
@@ -79,7 +79,7 @@ MCSymbol *WebAssemblyMCInstLower::GetExternalSymbolSymbol(
   // Clang-provided symbols.
   if (strcmp(Name, "__stack_pointer") == 0 || strcmp(Name, "__tls_base") == 0 ||
       strcmp(Name, "__memory_base") == 0 || strcmp(Name, "__table_base") == 0 ||
-      strcmp(Name, "__tls_size") == 0) {
+      strcmp(Name, "__tls_size") == 0 || strcmp(Name, "__tls_align") == 0) {
     bool Mutable =
         strcmp(Name, "__stack_pointer") == 0 || strcmp(Name, "__tls_base") == 0;
     WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);