[WinEH] Add llvm.eh.exceptionpointer intrinsic

Summary:
This intrinsic can be used to extract a pointer to the exception caught by
a given catchpad.  Its argument has token type and must be a `catchpad`.

Also clarify ExtendingLLVM documentation regarding overloaded intrinsics.


Reviewers: majnemer, andrew.w.kaylor, sanjoy, rnk

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12533

llvm-svn: 246752

docs/ExceptionHandling.rst

@@ -401,6 +401,20 @@ intrinsic serves as a placeholder to delimit code before a catch handler is
 outlined.  After the handler is outlined, this intrinsic is simply removed.
 
 
+.. _llvm.eh.exceptionpointer:
+
+``llvm.eh.exceptionpointer``
+----------------------
+
+.. code-block:: llvm
+
+  i8 addrspace(N)* @llvm.eh.padparam.pNi8(token %catchpad)
+
+
+This intrinsic retrieves a pointer to the exception caught by the given
+``catchpad``.
+
+
 SJLJ Intrinsics
 ---------------
 

docs/ExtendingLLVM.rst

@@ -49,9 +49,9 @@ function and then be turned into an instruction if warranted.
 
    Add an entry for your intrinsic.  Describe its memory access characteristics
    for optimization (this controls whether it will be DCE'd, CSE'd, etc). Note
-   that any intrinsic using the ``llvm_int_ty`` type for an argument will
+   that any intrinsic using one of the ``llvm_any*_ty`` types for an argument or
-   be deemed by ``tblgen`` as overloaded and the corresponding suffix will
+   return type will be deemed by ``tblgen`` as overloaded and the corresponding
-   be required on the intrinsic's name.
+   suffix will be required on the intrinsic's name.
 
 #. ``llvm/lib/Analysis/ConstantFolding.cpp``:
 

include/llvm/IR/Intrinsics.td

@@ -436,6 +436,11 @@ def int_eh_begincatch : Intrinsic<[], [llvm_ptr_ty, llvm_ptr_ty],
                                   [NoCapture<0>, NoCapture<1>]>;
 def int_eh_endcatch : Intrinsic<[], []>;
 
+// eh.exceptionpointer returns the pointer to the exception caught by
+// the given `catchpad`.
+def int_eh_exceptionpointer : Intrinsic<[llvm_anyptr_ty], [llvm_token_ty],
+                                        [IntrNoMem]>;
+
 // Represents the list of actions to take when an exception is thrown.
 def int_eh_actions : Intrinsic<[llvm_ptr_ty], [llvm_vararg_ty], []>;
 

lib/IR/Verifier.cpp

@@ -3681,6 +3681,11 @@ void Verifier::visitIntrinsicCallSite(Intrinsic::ID ID, CallSite CS) {
            "gc.relocate: relocating a pointer shouldn't change its address space", CS);
     break;
   }
+  case Intrinsic::eh_exceptionpointer: {
+    Assert(isa<CatchPadInst>(CS.getArgOperand(0)),
+           "eh.exceptionpointer argument must be a catchpad", CS);
+    break;
+  }
   };
 }
 

test/CodeGen/WinEH/wineh-intrinsics-invalid.ll

@@ -0,0 +1,26 @@
+; RUN: sed -e s/.T1:// %s | not opt -lint -disable-output 2>&1 | FileCheck --check-prefix=CHECK1 %s
+; RUN: sed -e s/.T2:// %s | not opt -lint -disable-output 2>&1 | FileCheck --check-prefix=CHECK2 %s
+
+target triple = "x86_64-pc-windows-msvc"
+
+declare void @f()
+
+;T1: declare i8* @llvm.eh.exceptionpointer.p0i8(i32)
+;T1:
+;T1: define void @test1() personality i32 (...)* @__CxxFrameHandler3 {
+;T1:   call i8* @llvm.eh.exceptionpointer.p0i8(i32 0)
+;T1:   ret void
+;T1: }
+;CHECK1: Intrinsic has incorrect argument type!
+;CHECK1-NEXT: i8* (i32)* @llvm.eh.exceptionpointer.p0i8
+
+;T2: declare i8* @llvm.eh.exceptionpointer.p0i8(token)
+;T2:
+;T2: define void @test2() personality i32 (...)* @__CxxFrameHandler3 {
+;T2:   call i8* @llvm.eh.exceptionpointer.p0i8(token undef)
+;T2:   ret void
+;T2: }
+;CHECK2: eh.exceptionpointer argument must be a catchpad
+;CHECK2-NEXT:  call i8* @llvm.eh.exceptionpointer.p0i8(token undef)
+
+declare i32 @__CxxFrameHandler3(...)

test/CodeGen/WinEH/wineh-intrinsics.ll

@@ -0,0 +1,46 @@
+; RUN: opt -lint -disable-output < %s
+
+; This test is meant to prove that the verifier does not report errors for correct
+; use of the llvm.eh.exceptionpointer intrinsic.
+
+target triple = "x86_64-pc-windows-msvc"
+
+declare i8* @llvm.eh.exceptionpointer.p0i8(token)
+declare i8 addrspace(1)* @llvm.eh.exceptionpointer.p1i8(token)
+
+declare void @f(...)
+
+define void @test1() personality i32 (...)* @__CxxFrameHandler3 {
+entry:
+  invoke void (...) @f(i32 1)
+     to label %exit unwind label %catchpad
+catchpad:
+  %catch = catchpad [i32 1] to label %do_catch unwind label %catchend
+do_catch:
+  %exn = call i8* @llvm.eh.exceptionpointer.p0i8(token %catch)
+  call void (...) @f(i8* %exn)
+  catchret %catch to label %exit
+catchend:
+  catchendpad unwind to caller
+exit:
+  ret void
+}
+
+define void @test2() personality i32 (...)* @ProcessManagedException {
+entry:
+  invoke void (...) @f(i32 1)
+     to label %exit unwind label %catchpad
+catchpad:
+  %catch = catchpad [i32 1] to label %do_catch unwind label %catchend
+do_catch:
+  %exn = call i8 addrspace(1)* @llvm.eh.exceptionpointer.p1i8(token %catch)
+  call void (...) @f(i8 addrspace(1)* %exn)
+  catchret %catch to label %exit
+catchend:
+  catchendpad unwind to caller
+exit:
+  ret void
+}
+
+declare i32 @__CxxFrameHandler3(...)
+declare i32 @ProcessManagedException(...)