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| author | Mark Seaborn <mseaborn@chromium.org> | 2014-03-20 19:54:47 +0000 |
|---|---|---|
| committer | Mark Seaborn <mseaborn@chromium.org> | 2014-03-20 19:54:47 +0000 |
| commit | 9bb9615e1fd8e3d2654d3fe394ee6f486a0cb8a5 (patch) | |
| tree | d1baa3bc6eb39e5dfb5656dac0c443b0aed83b69 /docs/Passes.rst | |
| parent | 56210e69eb3e26cd62391055e2054bf34342c119 (diff) | |
| download | llvm-9bb9615e1fd8e3d2654d3fe394ee6f486a0cb8a5.tar.gz llvm-9bb9615e1fd8e3d2654d3fe394ee6f486a0cb8a5.tar.bz2 llvm-9bb9615e1fd8e3d2654d3fe394ee6f486a0cb8a5.tar.xz | |
Remove LowerInvoke's obsolete "-enable-correct-eh-support" option
This option caused LowerInvoke to generate code using SJLJ-based
exception handling, but there is no code left that interprets the
jmp_buf stack that the resulting code maintained (llvm.sjljeh.jblist).
This option has been obsolete for a while, and replaced by
SjLjEHPrepare.
This leaves the default behaviour of LowerInvoke, which is to convert
invokes to calls.
Differential Revision: http://llvm-reviews.chandlerc.com/D3136
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204388 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/Passes.rst')
| -rw-r--r-- | docs/Passes.rst | 31 |
1 files changed, 6 insertions, 25 deletions
diff --git a/docs/Passes.rst b/docs/Passes.rst index 029e472bcd..a288933b7b 100644 --- a/docs/Passes.rst +++ b/docs/Passes.rst @@ -893,33 +893,14 @@ this would require knowledge of the entire call graph of the program including any libraries which may not be available in bitcode form); it simply lowers every atomic intrinsic. -``-lowerinvoke``: Lower invoke and unwind, for unwindless code generators -------------------------------------------------------------------------- +``-lowerinvoke``: Lower invokes to calls, for unwindless code generators +------------------------------------------------------------------------ This transformation is designed for use by code generators which do not yet -support stack unwinding. This pass supports two models of exception handling -lowering, the "cheap" support and the "expensive" support. - -"Cheap" exception handling support gives the program the ability to execute any -program which does not "throw an exception", by turning "``invoke``" -instructions into calls and by turning "``unwind``" instructions into calls to -``abort()``. If the program does dynamically use the "``unwind``" instruction, -the program will print a message then abort. - -"Expensive" exception handling support gives the full exception handling -support to the program at the cost of making the "``invoke``" instruction -really expensive. It basically inserts ``setjmp``/``longjmp`` calls to emulate -the exception handling as necessary. - -Because the "expensive" support slows down programs a lot, and EH is only used -for a subset of the programs, it must be specifically enabled by the -``-enable-correct-eh-support`` option. - -Note that after this pass runs the CFG is not entirely accurate (exceptional -control flow edges are not correct anymore) so only very simple things should -be done after the ``lowerinvoke`` pass has run (like generation of native -code). This should not be used as a general purpose "my LLVM-to-LLVM pass -doesn't support the ``invoke`` instruction yet" lowering pass. +support stack unwinding. This pass converts ``invoke`` instructions to +``call`` instructions, so that any exception-handling ``landingpad`` blocks +become dead code (which can be removed by running the ``-simplifycfg`` pass +afterwards). ``-lowerswitch``: Lower ``SwitchInst``\ s to branches ----------------------------------------------------- |