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context: update documentation related to FPU registers and calling conventions

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[SVN r78070]
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Oliver Kowalke
2012-04-18 18:33:57 +00:00
parent a8dddfee04
commit 1956ebde6e
2 changed files with 6 additions and 3 deletions
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doc/rationale.qbk
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@@ -98,8 +98,10 @@ already converted. Unfortunately Windows XP + SP 2/3 defines
[heading i386]
"The FpCsr and the MxCsr register must be saved an restored before any call or return
"The FpCsr and the MxCsr register must be saved and restored before any call or return
by any procedure that needs to modify them ..."
[footnote [@boost:/libs/context/doc/pdf/calling-conventions.pdf 'Calling Conventions',
Agner Fog]].
[heading x86_64]
@@ -127,10 +129,11 @@ context switches. There is no explicit calling convention for these registers."
'Legacy Floating-Point Support']].
"The 64-bit Microsoft compiler does not use ST(0)-ST(7)/MM0-MM7".
[footnote [@ 'Calling Conventions', Agner Fog]].
[footnote [@boost:/libs/context/doc/pdf/calling-conventions.pdf 'Calling Conventions',
Agner Fog]].
Conclusion: because no explicit calling convetion exists and MS compiler do not use those
registers __start_fcontext__ and __jump_fcontext__ do not preserve those registers.
registers, those registers will not be preserved.
"XMM6-XMM15 must be preserved"
[footnote [@http://msdn.microsoft.com/en-us/library/9z1stfyw%28v=vs.90%29.aspx MSDN