The return address may not point to an area covered by the debug infos
so we hope for the best and decrement the address so that it points to
the caller instruction.
This modifies the build process of Zig to put all of the source files
into libcompiler.a, except main.cpp and userland.cpp.
Next, the build process links main.cpp, userland.cpp, and libcompiler.a
into zig1. userland.cpp is a shim for functions that will later be
replaced with self-hosted implementations.
Next, the build process uses zig1 to build src-self-hosted/stage1.zig
into libuserland.a, which does not depend on any of the things that
are shimmed in userland.cpp, such as translate-c.
Finally, the build process re-links main.cpp and libcompiler.a, except
with libuserland.a instead of userland.cpp. Now the shims are replaced
with .zig code. This provides all of the Zig standard library to the
stage1 C++ compiler, and enables us to move certain things to userland,
such as translate-c.
As a proof of concept I have made the `zig zen` command use text defined
in userland. I added `zig translate-c-2` which is a work-in-progress
reimplementation of translate-c in userland, which currently calls
`std.debug.panic("unimplemented")` and you can see the stack trace makes
it all the way back into the C++ main() function (Thanks LemonBoy for
improving that!).
This could potentially let us move other things into userland, such as
hashing algorithms, the entire cache system, .d file parsing, pretty
much anything that libuserland.a itself doesn't need to depend on.
This can also let us have `zig fmt` in stage1 without the overhead
of child process execution, and without the initial compilation delay
before it gets cached.
See #1964
* Correct parsing of DWARF line_info section
* Fix reading of udata/sdata encoded attributes
* Add definition for DW_AT_alignment
Even though it's been standardized in DWARF5 some compilers produce it
anyway for DWARF4 infos too.
* Fix reading of reference attributes
* Distinguish between absolute/relative addresses
This effectively takes one-bit from the length field and uses it as the
sign bit. It reduces the size of an Int from 40 bits to 32 bits on a
64-bit arch.
This also reduces std.Rational from 80 bits to 64 bits.
A constant Int is one which has a value of null for its allocator field.
It cannot be resized or have its limbs written. Any attempt made to
write to it will be caught with a runtime panic.
This removes the compiler_rt.setXmm0 hack. Instead, for
the functions that use i128 or u128 in their parameter and
return types, we use `@Vector(2, u64)` which generates
the LLVM IR `<2 x i64>` type that matches what Clang
generates for `typedef int ti_int __attribute__ ((mode (TI)))`
when targeting Windows x86_64.
