[cfe-dev] 回复:Re: Re: Re: Will clang 4.0 support the new LLVM Exception Handleing instructions ?

via cfe-dev cfe-dev at lists.llvm.org
Tue Sep 6 22:27:18 PDT 2016


Get it. Thank you for your information.

----- 原始邮件 -----
发件人:David Majnemer <david.majnemer at gmail.com>
收件人:bluedream_zqs at sina.com
抄送人:cfe-dev <cfe-dev at lists.llvm.org>
主题:Re: Re: Re: [cfe-dev] Will clang 4.0 support the new LLVM Exception Handleing instructions ?
日期:2016年09月07日 13点11分



On Tue, Sep 6, 2016 at 10:00 PM,  <bluedream_zqs at sina.com> wrote:
Does it mean, LLVM supports the new eh instructions early before and clang use it to implement the MSVC exception handling. What 4.0 did is just export those instructions into the documentation. And we won't change the clang eh implementation in fact, still use the landingpad inst for all platform ?

We don't use LandingPadInst for all platforms, we use it on all non-MSVC compatible platforms.  MSVC compatible EH uses the new mechanism. 
----- 原始邮件 -----
发件人:David Majnemer <david.majnemer at gmail.com>
收件人:bluedream_zqs at sina.com
抄送人:cfe-dev <cfe-dev at lists.llvm.org>
主题:Re: Re: [cfe-dev] Will clang 4.0 support the new LLVM Exception Handleing instructions ?
日期:2016年09月07日 12点47分



On Tue, Sep 6, 2016 at 9:37 PM,  <bluedream_zqs at sina.com> wrote:

----- 原始邮件 -----
发件人:David Majnemer <david.majnemer at gmail.com>
收件人:bluedream_zqs at sina.com
抄送人:cfe-dev <cfe-dev at lists.llvm.org>
主题:Re: [cfe-dev] Will clang 4.0 support the new LLVM Exception Handleing instructions ?
日期:2016年09月07日 12点29分

Do we have any plan to make the new eh instructions as the default implementation for all platforms ?
No, that would result in a performance regression for non-MSVC exception handling. 

On Tue, Sep 6, 2016 at 6:49 PM, via cfe-dev <cfe-dev at lists.llvm.org> wrote:
 LLVM support new eh instructions.(http://llvm.org/docs/ExceptionHandling.html#new-exception-handling-instructions) Clang still use the old landingpad inst to support the C++ exceptions. Do we have any plan to enable the support of the new exception instructions ?

Clang already supports the new C++ exception handling instructions, it uses them exclusively to implement MSVC compatible exception handling.  The landingpad scheme is retained because it provides a degree of flexibility (and thus optimization opportunities) which isn't available in the new instructions. 
Thank you.

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