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majnemermajnemer
committedJul 31, 2015
New EH representation for MSVC compatibility
This introduces new instructions neccessary to implement MSVC-compatible exception handling support. Most of the middle-end and none of the back-end haven't been audited or updated to take them into account. Differential Revision: http://reviews.llvm.org/D11097 llvm-svn: 243766
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‎llvm/docs/LangRef.rst

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@@ -4741,7 +4741,12 @@ control flow, not values (the one exception being the
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The terminator instructions are: ':ref:`ret <i_ret>`',
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':ref:`br <i_br>`', ':ref:`switch <i_switch>`',
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':ref:`indirectbr <i_indirectbr>`', ':ref:`invoke <i_invoke>`',
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':ref:`resume <i_resume>`', and ':ref:`unreachable <i_unreachable>`'.
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':ref:`resume <i_resume>`', ':ref:`catchpad <i_catchpad>`',
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':ref:`catchendpad <i_catchendpad>`',
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':ref:`catchret <i_catchret>`',
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':ref:`cleanupret <i_cleanupret>`',
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':ref:`terminatepad <i_terminatepad>`',
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and ':ref:`unreachable <i_unreachable>`'.
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.. _i_ret:
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@@ -5095,6 +5100,301 @@ Example:
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resume { i8*, i32 } %exn
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.. _i_catchpad:
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'``catchpad``' Instruction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax:
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"""""""
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::
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<resultval> = catchpad <resultty> [<args>*]
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to label <normal label> unwind label <exception label>
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Overview:
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"""""""""
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The '``catchpad``' instruction is used by `LLVM's exception handling
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system <ExceptionHandling.html#overview>`_ to specify that a basic block
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is a catch block --- one where a personality routine attempts to transfer
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control to catch an exception.
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The ``args`` correspond to whatever information the personality
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routine requires to know if this is an appropriate place to catch the
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exception. Control is tranfered to the ``exception`` label if the
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``catchpad`` is not an appropriate handler for the in-flight exception.
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The ``normal`` label should contain the code found in the ``catch``
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portion of a ``try``/``catch`` sequence. It defines values supplied by
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the :ref:`personality function <personalityfn>` upon re-entry to the
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function. The ``resultval`` has the type ``resultty``.
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Arguments:
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""""""""""
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The instruction takes a list of arbitrary values which are interpreted
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by the :ref:`personality function <personalityfn>`.
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The ``catchpad`` must be provided a ``normal`` label to transfer control
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to if the ``catchpad`` matches the exception and an ``exception``
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label to transfer control to if it doesn't.
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Semantics:
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""""""""""
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The '``catchpad``' instruction defines the values which are set by the
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:ref:`personality function <personalityfn>` upon re-entry to the function, and
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therefore the "result type" of the ``catchpad`` instruction. As with
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calling conventions, how the personality function results are
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represented in LLVM IR is target specific.
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When the call stack is being unwound due to an exception being thrown,
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the exception is compared against the ``args``. If it doesn't match,
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then control is transfered to the ``exception`` basic block.
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The ``catchpad`` instruction has several restrictions:
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- A catch block is a basic block which is the unwind destination of
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an exceptional instruction.
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- A catch block must have a '``catchpad``' instruction as its
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first non-PHI instruction.
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- A catch block's ``exception`` edge must refer to a catch block or a
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catch-end block.
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- There can be only one '``catchpad``' instruction within the
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catch block.
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- A basic block that is not a catch block may not include a
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'``catchpad``' instruction.
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- It is undefined behavior for control to transfer from a ``catchpad`` to a
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``cleanupret`` without first executing a ``catchret`` and a subsequent
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``cleanuppad``.
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- It is undefined behavior for control to transfer from a ``catchpad`` to a
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``ret`` without first executing a ``catchret``.
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Example:
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""""""""
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.. code-block:: llvm
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;; A catch block which can catch an integer.
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%res = catchpad { i8*, i32 } [i8** @_ZTIi]
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to label %int.handler unwind label %terminate
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.. _i_catchendpad:
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'``catchendpad``' Instruction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax:
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"""""""
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::
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catchendpad unwind label <nextaction>
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catchendpad unwind to caller
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Overview:
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"""""""""
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The '``catchendpad``' instruction is used by `LLVM's exception handling
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system <ExceptionHandling.html#overview>`_ to communicate to the
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:ref:`personality function <personalityfn>` which invokes are associated
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with a chain of :ref:`catchpad <i_catchpad>` instructions.
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The ``nextaction`` label indicates where control should transfer to if
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none of the ``catchpad`` instructions are suitable for catching the
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in-flight exception.
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If a ``nextaction`` label is not present, the instruction unwinds out of
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its parent function. The
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:ref:`personality function <personalityfn>` will continue processing
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exception handling actions in the caller.
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Arguments:
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""""""""""
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The instruction optionally takes a label, ``nextaction``, indicating
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where control should transfer to if none of the preceding
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``catchpad`` instructions are suitable for the in-flight exception.
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Semantics:
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""""""""""
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When the call stack is being unwound due to an exception being thrown
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and none of the constituent ``catchpad`` instructions match, then
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control is transfered to ``nextaction`` if it is present. If it is not
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present, control is transfered to the caller.
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The ``catchendpad`` instruction has several restrictions:
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- A catch-end block is a basic block which is the unwind destination of
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an exceptional instruction.
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- A catch-end block must have a '``catchendpad``' instruction as its
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first non-PHI instruction.
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- There can be only one '``catchendpad``' instruction within the
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catch block.
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- A basic block that is not a catch-end block may not include a
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'``catchendpad``' instruction.
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- Exactly one catch block may unwind to a ``catchendpad``.
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- The unwind target of invokes between a ``catchpad`` and a
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corresponding ``catchret`` must be its ``catchendpad``.
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Example:
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""""""""
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.. code-block:: llvm
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catchendpad unwind label %terminate
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catchendpad unwind to caller
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.. _i_catchret:
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'``catchret``' Instruction
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax:
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"""""""
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::
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catchret label <normal>
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Overview:
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"""""""""
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The '``catchret``' instruction is a terminator instruction that has a
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single successor.
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Arguments:
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""""""""""
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The '``catchret``' instruction requires one argument which specifies
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where control will transfer to next.
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Semantics:
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""""""""""
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The '``catchret``' instruction ends the existing (in-flight) exception
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whose unwinding was interrupted with a
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:ref:`catchpad <i_catchpad>` instruction.
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The :ref:`personality function <personalityfn>` gets a chance to execute
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arbitrary code to, for example, run a C++ destructor.
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Control then transfers to ``normal``.
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Example:
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""""""""
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.. code-block:: llvm
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catchret label %continue
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.. _i_cleanupret:
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'``cleanupret``' Instruction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax:
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"""""""
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::
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cleanupret <type> <value> unwind label <continue>
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cleanupret <type> <value> unwind to caller
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Overview:
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"""""""""
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The '``cleanupret``' instruction is a terminator instruction that has
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an optional successor.
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Arguments:
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""""""""""
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The '``cleanupret``' instruction requires one argument, which must have the
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same type as the result of any '``cleanuppad``' instruction in the same
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function. It also has an optional successor, ``continue``.
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Semantics:
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""""""""""
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The '``cleanupret``' instruction indicates to the
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:ref:`personality function <personalityfn>` that one
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:ref:`cleanuppad <i_cleanuppad>` it transferred control to has ended.
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It transfers control to ``continue`` or unwinds out of the function.
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Example:
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""""""""
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.. code-block:: llvm
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cleanupret void unwind to caller
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cleanupret { i8*, i32 } %exn unwind label %continue
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.. _i_terminatepad:
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'``terminatepad``' Instruction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax:
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"""""""
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::
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terminatepad [<args>*] unwind label <exception label>
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terminatepad [<args>*] unwind to caller
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Overview:
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"""""""""
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The '``terminatepad``' instruction is used by `LLVM's exception handling
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system <ExceptionHandling.html#overview>`_ to specify that a basic block
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is a terminate block --- one where a personality routine may decide to
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terminate the program.
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The ``args`` correspond to whatever information the personality
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routine requires to know if this is an appropriate place to terminate the
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program. Control is transferred to the ``exception`` label if the
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personality routine decides not to terminate the program for the
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in-flight exception.
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Arguments:
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""""""""""
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The instruction takes a list of arbitrary values which are interpreted
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by the :ref:`personality function <personalityfn>`.
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The ``terminatepad`` may be given an ``exception`` label to
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transfer control to if the in-flight exception matches the ``args``.
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Semantics:
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""""""""""
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When the call stack is being unwound due to an exception being thrown,
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the exception is compared against the ``args``. If it matches,
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then control is transfered to the ``exception`` basic block. Otherwise,
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the program is terminated via personality-specific means. Typically,
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the first argument to ``terminatepad`` specifies what function the
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personality should defer to in order to terminate the program.
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The ``terminatepad`` instruction has several restrictions:
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- A terminate block is a basic block which is the unwind destination of
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an exceptional instruction.
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- A terminate block must have a '``terminatepad``' instruction as its
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first non-PHI instruction.
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- There can be only one '``terminatepad``' instruction within the
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terminate block.
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- A basic block that is not a terminate block may not include a
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'``terminatepad``' instruction.
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Example:
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""""""""
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.. code-block:: llvm
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;; A terminate block which only permits integers.
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terminatepad [i8** @_ZTIi] unwind label %continue
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.. _i_unreachable:
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'``unreachable``' Instruction
@@ -8052,6 +8352,72 @@ Example:
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catch i8** @_ZTIi
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filter [1 x i8**] [@_ZTId]
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.. _i_cleanuppad:
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'``cleanuppad``' Instruction
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Syntax:
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"""""""
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::
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<resultval> = cleanuppad <resultty> [<args>*]
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Overview:
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"""""""""
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The '``cleanuppad``' instruction is used by `LLVM's exception handling
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system <ExceptionHandling.html#overview>`_ to specify that a basic block
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is a cleanup block --- one where a personality routine attempts to
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transfer control to run cleanup actions.
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The ``args`` correspond to whatever additional
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information the :ref:`personality function <personalityfn>` requires to
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execute the cleanup.
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The ``resultval`` has the type ``resultty``.
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Arguments:
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""""""""""
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The instruction takes a list of arbitrary values which are interpreted
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by the :ref:`personality function <personalityfn>`.
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Semantics:
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""""""""""
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The '``cleanuppad``' instruction defines the values which are set by the
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:ref:`personality function <personalityfn>` upon re-entry to the function, and
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therefore the "result type" of the ``cleanuppad`` instruction. As with
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calling conventions, how the personality function results are
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represented in LLVM IR is target specific.
8393+
8394+
When the call stack is being unwound due to an exception being thrown,
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the :ref:`personality function <personalityfn>` transfers control to the
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``cleanuppad`` with the aid of the personality-specific arguments.
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8398+
The ``cleanuppad`` instruction has several restrictions:
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- A cleanup block is a basic block which is the unwind destination of
8401+
an exceptional instruction.
8402+
- A cleanup block must have a '``cleanuppad``' instruction as its
8403+
first non-PHI instruction.
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- There can be only one '``cleanuppad``' instruction within the
8405+
cleanup block.
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- A basic block that is not a cleanup block may not include a
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'``cleanuppad``' instruction.
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- It is undefined behavior for control to transfer from a ``cleanuppad`` to a
8409+
``catchret`` without first executing a ``cleanupret`` and a subsequent
8410+
``catchpad``.
8411+
- It is undefined behavior for control to transfer from a ``cleanuppad`` to a
8412+
``ret`` without first executing a ``cleanupret``.
8413+
8414+
Example:
8415+
""""""""
8416+
8417+
.. code-block:: llvm
8418+
8419+
%res = cleanuppad { i8*, i32 } [label %nextaction]
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80558421
.. _intrinsics:
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80578423
Intrinsic Functions

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