[WebAssembly] Implement __builtin_return_address for emscripten

Summary:
In this patch, `ISD::RETURNADDR` is lowered on the emscripten target
to the new Emscripten runtime function `emscripten_return_address`, which
implements the functionality.

Patch by Guanzhong Chen

Reviewers: tlively, aheejin

Reviewed By: tlively

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62210

llvm-svn: 361454

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
index 2bc602034ba..5a86b27cac0 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRuntimeLibcallSignatures.cpp
@@ -325,6 +325,9 @@ struct RuntimeLibcallSignatureTable {
     // __stack_chk_fail
     Table[RTLIB::STACKPROTECTOR_CHECK_FAIL] = func;
 
+    // Return address handling
+    Table[RTLIB::RETURN_ADDRESS] = i32_func_i32;
+
     // Element-wise Atomic memory
     // TODO: Fix these when we implement atomic support
     Table[RTLIB::MEMCPY_ELEMENT_UNORDERED_ATOMIC_1] = unsupported;
@@ -499,6 +502,8 @@ struct StaticLibcallNameMap {
     // consistent with the f64 and f128 names.
     Map["__extendhfsf2"] = RTLIB::FPEXT_F16_F32;
     Map["__truncsfhf2"] = RTLIB::FPROUND_F32_F16;
+
+    Map["emscripten_return_address"] = RTLIB::RETURN_ADDRESS;
   }
 };