[WebAssembly] Implement __builtin_wasm_tls_base intrinsic

[quantum]

Summary

Add __builtin_wasm_tls_base so that LeakSanitizer can find the thread-local
block and scan through it for memory leaks.

[aheejin]

What does this return when __wasm_init_tls has not been called?

[quantum]

In D64900#1590715, @aheejin wrote:

What does this return when __wasm_init_tls has not been called?

It returns 0, which I think is fine.

[sunfish]

cfe/trunk/include/clang/Basic/BuiltinsWebAssembly.def

34 ↗

(On Diff #210632)

This can also be "p" for "pure", which despite the name, just means there are no mutating side effects.

clang/include/clang/Basic/BuiltinsWebAssembly.def

 BUILTIN(__builtin_wasm_memory_grow, "zIiz", "n")
 
 // Bulk memory builtins
 TARGET_BUILTIN(__builtin_wasm_memory_init, "vIUiIUiv*UiUi", "", "bulk-memory")
 TARGET_BUILTIN(__builtin_wasm_data_drop, "vIUi", "", "bulk-memory")
 
 // Thread-local storage
 TARGET_BUILTIN(__builtin_wasm_tls_size, "z", "nc", "bulk-memory")
+TARGET_BUILTIN(__builtin_wasm_tls_base, "v*", "n", "bulk-memory")
 
 // Floating point min/max
 BUILTIN(__builtin_wasm_min_f32, "fff", "nc")
 BUILTIN(__builtin_wasm_max_f32, "fff", "nc")
 BUILTIN(__builtin_wasm_min_f64, "ddd", "nc")
 BUILTIN(__builtin_wasm_max_f64, "ddd", "nc")
 
 // Exception handling builtins.

clang/lib/CodeGen/CGBuiltin.cpp

case WebAssembly::BI__builtin_wasm_data_drop: {
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_data_drop);
     return Builder.CreateCall(Callee, {Arg});
   }
   case WebAssembly::BI__builtin_wasm_tls_size: {
     llvm::Type *ResultType = ConvertType(E->getType());
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_tls_size, ResultType);
     return Builder.CreateCall(Callee);
   }
+  case WebAssembly::BI__builtin_wasm_tls_base: {
+    Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_tls_base);
+    return Builder.CreateCall(Callee);
+  }
   case WebAssembly::BI__builtin_wasm_throw: {
     Value *Tag = EmitScalarExpr(E->getArg(0));
     Value *Obj = EmitScalarExpr(E->getArg(1));
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_throw);
     return Builder.CreateCall(Callee, {Tag, Obj});
   }
   case WebAssembly::BI__builtin_wasm_rethrow_in_catch: {
     Function *Callee = CGM.getIntrinsic(Intrinsic::wasm_rethrow_in_catch);

clang/test/CodeGen/builtins-wasm.c

 }
 
 __SIZE_TYPE__ tls_size() {
   return __builtin_wasm_tls_size();
   // WEBASSEMBLY32: call i32 @llvm.wasm.tls.size.i32()
   // WEBASSEMBLY64: call i64 @llvm.wasm.tls.size.i64()
 }
 
+void *tls_base() {
+  return __builtin_wasm_tls_base();
+  // WEBASSEMBLY: call i8* @llvm.wasm.tls.base()
+}
+
 void throw(void *obj) {
   return __builtin_wasm_throw(0, obj);
   // WEBASSEMBLY32: call void @llvm.wasm.throw(i32 0, i8* %{{.*}})
   // WEBASSEMBLY64: call void @llvm.wasm.throw(i32 0, i8* %{{.*}})
 }
 
 void rethrow_in_catch(void) {
   return __builtin_wasm_rethrow_in_catch();

llvm/include/llvm/IR/IntrinsicsWebAssembly.td

 // Thread-local storage intrinsics
 //===----------------------------------------------------------------------===//
 
 def int_wasm_tls_size :
   Intrinsic<[llvm_anyint_ty],
             [],
             [IntrNoMem, IntrSpeculatable]>;
 
+def int_wasm_tls_base :
+  Intrinsic<[llvm_ptr_ty],
+            [],
+            [IntrReadMem]>;
+
 } // TargetPrefix = "wasm"

llvm/lib/Target/WebAssembly/WebAssemblyISelDAGToDAG.cpp

case Intrinsic::wasm_tls_size: {
           WebAssembly::GLOBAL_GET_I32, DL, PtrVT,
           CurDAG->getTargetExternalSymbol("__tls_size", MVT::i32));
       ReplaceNode(Node, TLSSize);
       return;
     }
     }
     break;
   }
+  case ISD::INTRINSIC_W_CHAIN: {
+    unsigned IntNo = cast<ConstantSDNode>(Node->getOperand(1))->getZExtValue();
+    switch (IntNo) {
+    case Intrinsic::wasm_tls_base: {
+      MVT PtrVT = TLI->getPointerTy(CurDAG->getDataLayout());
+      assert(PtrVT == MVT::i32 && "only wasm32 is supported for now");
+
+      MachineSDNode *TLSBase = CurDAG->getMachineNode(
+          WebAssembly::GLOBAL_GET_I32, DL, MVT::i32,
+          CurDAG->getTargetExternalSymbol("__tls_base", PtrVT),
+          Node->getOperand(0));
+      ReplaceNode(Node, TLSBase);
+      return;
+    }
+    }
+    break;
+  }
 
   default:
     break;
   }
 
   // Select the default instruction.
   SelectCode(Node);
 }

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

 ; CHECK-NEXT: .functype tls_size () -> (i32)
 define i32 @tls_size() {
 ; CHECK-NEXT: global.get __tls_size
 ; CHECK-NEXT: return
   %1 = call i32 @llvm.wasm.tls.size.i32()
   ret i32 %1
 }
 
+; CHECK-LABEL: tls_base:
+; CHECK-NEXT: .functype tls_base () -> (i32)
+define i8* @tls_base() {
+; CHECK-NEXT: global.get __tls_base
+; CHECK-NEXT: return
+  %1 = call i8* @llvm.wasm.tls.base()
+  ret i8* %1
+}
+
 ; CHECK: .type tls,@object
 ; TLS-NEXT: .section .tbss.tls,"",@
 ; NO-TLS-NEXT: .section .bss.tls,"",@
 ; CHECK-NEXT: .p2align 2
 ; CHECK-NEXT: tls:
 ; CHECK-NEXT: .int32 0
 @tls = internal thread_local global i32 0
 
 declare i32 @llvm.wasm.tls.size.i32()
+declare i8* @llvm.wasm.tls.base()