0008-Part-8.-Add-Intel-CET-support-for-EH-in-libgcc

["Tsimbalist, Igor V" <igor dot v dot tsimbalist at intel dot com>]

Part#8. Add Intel CET support for EH in libgcc.

Control-flow Enforcement Technology (CET), published by Intel, introduces
the Shadow Stack feature, which ensures a return from a function is done
to exactly the same location from where the function was called. When EH
is present the control-flow transfer may skip some stack frames and the
shadow stack has to be adjusted not to signal a violation of a
control-flow transfer. It's done by counting a number of skipping frames
and adjusting shadow stack pointer by this number.

Having new semantic of the 'ret' instruction if CET is supported in HW
the 'ret' instruction cannot be generated in ix86_expand_epilogue when
we are returning after EH is processed. Added a code in
ix86_expand_epilogue to adjust Shadow stack pointer and the indirect
jump is generated instead of 'ret'. As sp register is used during this
adjustment thus the argument in pro_epilogue_adjust_stack is changed
to update cfa_reg based on whether control-flow instrumentation is set.
Without updating the cfa_reg field there is an assert later in dwarf2
pass related to mismatch the stack register and cfa_reg value.

Attachment: 0008-Part-8.-Add-Intel-CET-support-for-EH-in-libgcc.patch
Description: 0008-Part-8.-Add-Intel-CET-support-for-EH-in-libgcc.patch