amd64 csu: microoptimize startup

Reorder operations to reduce moving the values among registers.
Use the LEA instruction to combine arithmetic with the moves.

Reviewed by: markj
Sponsored by: The F

amd64 csu: microoptimize startup

Reorder operations to reduce moving the values among registers.
Use the LEA instruction to combine arithmetic with the moves.

Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D49206

show more ...

amd64 crt1: Explicitly use a PLT entry for main in the PIC case.

This ensures GNU as generates a R_X86_64_PLT32 relocation instead of
R_X86_64_32.

Reviewed by: kib
Fixes: c969310c992a csu: Impleme

amd64 crt1: Explicitly use a PLT entry for main in the PIC case.

This ensures GNU as generates a R_X86_64_PLT32 relocation instead of
R_X86_64_32.

Reviewed by: kib
Fixes: c969310c992a csu: Implement _start using as to satisfy unwinders on x86_64
Differential Revision: https://reviews.freebsd.org/D41101

show more ...

csu: Implement _start using as to satisfy unwinders on x86_64

The right unwinding stop indicator should be CFI-undefined PC.
https://dwarfstd.org/doc/Dwarf3.pdf - page 118:
If a Return Address regis

csu: Implement _start using as to satisfy unwinders on x86_64

The right unwinding stop indicator should be CFI-undefined PC.
https://dwarfstd.org/doc/Dwarf3.pdf - page 118:
If a Return Address register is defined in the virtual unwind table,
and its rule is undefined (for example, by DW_CFA_undefined), then
there is no return address and no call address, and the virtual
unwind of stack activations is complete.

This requires the crt code be built with unwind tables, for that remove
-fno-asynchronous-unwind-tables to enable unwind tables generation.

PR: 241562, 246322, 246537
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D40780

show more ...