[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, 5 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 8c7411fc305..dee1e207ef3 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -13924,6 +13924,11 @@ Value *CodeGenFunction::EmitWebAssemblyBuiltinExpr(unsigned BuiltinID,
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_tls_size, ResultType);
     return Builder.CreateCall(Callee);
   }
+  case WebAssembly::BI__builtin_wasm_tls_align: {
+    llvm::Type *ResultType = ConvertType(E->getType());
+    Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_tls_align, ResultType);
+    return Builder.CreateCall(Callee);
+  }
   case WebAssembly::BI__builtin_wasm_tls_base: {
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_tls_base);
     return Builder.CreateCall(Callee);