[Preallocated] Add @llvm.call.preallocated.teardown

This cleans up the stack allocated by a @llvm.call.preallocated.setup.
Should either call the teardown or the preallocated call to clean up the
stack. Calling both is UB.

Add LangRef.

Add verifier check that the token argument is a @llvm.call.preallocated.setup.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D83354

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 9e99f4d..cc2f6d1 100644 (file)
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -12103,6 +12103,65 @@ It is undefined behavior if this is called with a token from an
 preallocated call corresponding to the '``llvm.call.preallocated.setup``'
 has already been called.
 
+.. _int_call_preallocated_teardown:
+
+'``llvm.call.preallocated.teardown``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare i8* @llvm.call.preallocated.teardown(token %setup_token)
+
+Overview:
+"""""""""
+
+The '``llvm.call.preallocated.teardown``' intrinsic cleans up the stack
+created by a '``llvm.call.preallocated.setup``'.
+
+Semantics:
+""""""""""
+
+The token argument must be a '``llvm.call.preallocated.setup``'.
+
+The '``llvm.call.preallocated.teardown``' intrinsic cleans up the stack
+allocated by the corresponding '``llvm.call.preallocated.setup``'. Exactly
+one of this or the preallocated call must be called to prevent stack leaks.
+It is undefined behavior to call both a '``llvm.call.preallocated.teardown``'
+and the preallocated call for a given '``llvm.call.preallocated.setup``'.
+
+For example, if the stack is allocated for a preallocated call by a
+'``llvm.call.preallocated.setup``', then an initializer function called on an
+allocated argument throws an exception, there should be a
+'``llvm.call.preallocated.teardown``' in the exception handler to prevent
+stack leaks.
+
+Following the nesting rules in '``llvm.call.preallocated.setup``', nested
+calls to '``llvm.call.preallocated.setup``' and
+'``llvm.call.preallocated.teardown``' are allowed but must be properly
+nested.
+
+Example:
+""""""""
+
+.. code-block:: llvm
+
+        %cs = call token @llvm.call.preallocated.setup(i32 1)
+        %x = call i8* @llvm.call.preallocated.arg(token %cs, i32 0) preallocated(i32)
+        %y = bitcast i8* %x to i32*
+        invoke void @constructor(i32* %y) to label %conta unwind label %contb
+    conta:
+        call void @foo1(i32* preallocated(i32) %y) ["preallocated"(token %cs)]
+        ret void
+    contb:
+        %s = catchswitch within none [label %catch] unwind to caller
+    catch:
+        %p = catchpad within %s []
+        call void @llvm.call.preallocated.teardown(token %cs)
+        ret void
+
 Standard C Library Intrinsics
 -----------------------------
 

diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
index 433e249..9474122 100644 (file)
--- a/llvm/include/llvm/IR/Intrinsics.td
+++ b/llvm/include/llvm/IR/Intrinsics.td
@@ -534,6 +534,7 @@ def int_instrprof_value_profile : Intrinsic<[],
 
 def int_call_preallocated_setup : Intrinsic<[llvm_token_ty], [llvm_i32_ty]>;
 def int_call_preallocated_arg : Intrinsic<[llvm_ptr_ty], [llvm_token_ty, llvm_i32_ty]>;
+def int_call_preallocated_teardown : Intrinsic<[], [llvm_token_ty]>;
 
 //===------------------- Standard C Library Intrinsics --------------------===//
 //

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index b5e4ce9..8fa87b7 100644 (file)
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -4566,6 +4566,9 @@ void Verifier::visitIntrinsicCall(Intrinsic::ID ID, CallBase &Call) {
                "llvm.call.preallocated.alloc arg index must be between 0 and "
                "corresponding "
                "llvm.call.preallocated.setup's argument count");
+      } else if (Fn && Fn->getIntrinsicID() ==
+                           Intrinsic::call_preallocated_teardown) {
+        // nothing to do
       } else {
         Assert(!FoundCall, "Can have at most one call corresponding to a "
                            "llvm.call.preallocated.setup");
@@ -4614,6 +4617,14 @@ void Verifier::visitIntrinsicCall(Intrinsic::ID ID, CallBase &Call) {
            "call site attribute");
     break;
   }
+  case Intrinsic::call_preallocated_teardown: {
+    auto *Token = dyn_cast<CallBase>(Call.getArgOperand(0));
+    Assert(Token && Token->getCalledFunction()->getIntrinsicID() ==
+                        Intrinsic::call_preallocated_setup,
+           "llvm.call.preallocated.teardown token argument must be a "
+           "llvm.call.preallocated.setup");
+    break;
+  }
   case Intrinsic::gcroot:
   case Intrinsic::gcwrite:
   case Intrinsic::gcread:

diff --git a/llvm/test/Verifier/preallocated-invalid.ll b/llvm/test/Verifier/preallocated-invalid.ll
index 7fdab33..879d4ed 100644 (file)
--- a/llvm/test/Verifier/preallocated-invalid.ll
+++ b/llvm/test/Verifier/preallocated-invalid.ll
@@ -2,6 +2,7 @@
 
 declare token @llvm.call.preallocated.setup(i32)
 declare i8* @llvm.call.preallocated.arg(token, i32)
+declare void @llvm.call.preallocated.teardown(token)
 
 ; Fake LLVM intrinsic to return a token
 declare token @llvm.what()
@@ -136,3 +137,10 @@ define void @musttail_attr_no_match(i32* preallocated(i32) %a) {
     musttail call void @musttail_and_bundle(i32* %a)
     ret void
 }
+
+; CHECK: token argument must be a llvm.call.preallocated.setup
+define void @teardown_token_not_from_setup() {
+    %cs = call token @llvm.what()
+    call void @llvm.call.preallocated.teardown(token %cs)
+    ret void
+}

diff --git a/llvm/test/Verifier/preallocated-valid.ll b/llvm/test/Verifier/preallocated-valid.ll
index 483493c..bbb663b 100644 (file)
--- a/llvm/test/Verifier/preallocated-valid.ll
+++ b/llvm/test/Verifier/preallocated-valid.ll
@@ -2,11 +2,16 @@
 
 declare token @llvm.call.preallocated.setup(i32)
 declare i8* @llvm.call.preallocated.arg(token, i32)
+declare void @llvm.call.preallocated.teardown(token)
+
+declare i32 @__CxxFrameHandler3(...)
 
 declare void @foo1(i32* preallocated(i32))
 declare i64 @foo1_i64(i32* preallocated(i32))
 declare void @foo2(i32* preallocated(i32), i32*, i32* preallocated(i32))
 
+declare void @constructor(i32*)
+
 define void @preallocated() {
     %cs = call token @llvm.call.preallocated.setup(i32 1)
     %x = call i8* @llvm.call.preallocated.arg(token %cs, i32 0) preallocated(i32)
@@ -40,12 +45,34 @@ define void @preallocated_num_args() {
     ret void
 }
 
-define void @preallocate_musttail(i32* preallocated(i32) %a) {
+define void @preallocated_musttail(i32* preallocated(i32) %a) {
     musttail call void @foo1(i32* preallocated(i32) %a)
     ret void
 }
 
-define i64 @preallocate_musttail_i64(i32* preallocated(i32) %a) {
+define i64 @preallocated_musttail_i64(i32* preallocated(i32) %a) {
     %r = musttail call i64 @foo1_i64(i32* preallocated(i32) %a)
     ret i64 %r
 }
+
+define void @preallocated_teardown() {
+    %cs = call token @llvm.call.preallocated.setup(i32 1)
+    call void @llvm.call.preallocated.teardown(token %cs)
+    ret void
+}
+
+define void @preallocated_teardown_invoke() personality i8* bitcast (i32 (...)* @__CxxFrameHandler3 to i8*) {
+    %cs = call token @llvm.call.preallocated.setup(i32 1)
+    %x = call i8* @llvm.call.preallocated.arg(token %cs, i32 0) preallocated(i32)
+    %y = bitcast i8* %x to i32*
+    invoke void @constructor(i32* %y) to label %conta unwind label %contb
+conta:
+    call void @foo1(i32* preallocated(i32) %y) ["preallocated"(token %cs)]
+    ret void
+contb:
+    %s = catchswitch within none [label %catch] unwind to caller
+catch:
+    %p = catchpad within %s []
+    call void @llvm.call.preallocated.teardown(token %cs)
+    ret void
+}