When extern was added, the rv64 code switched regular globals from
using la (a pseudo-instruction that uses pc-relative addressing
with auipc + addi) to lui + addi (absolute addressing). Presumably,
this was done to match gcc's output with -fPIC and -fno-PIC
respectively. However, the key difference here is actually the
directive `%option pic` vs `%option nopic`, which determines whether
la uses the GOT or not.
This broke linking as PIE (for instance in compilers with
--enable-default-pie), even when there are no global references
outside the executable. The other architectures always use pc-relative
addressing, so rv64 should do the same.
It turns out there are more specific pseudo-instructions lla and
lga we can use instead. lla uses auipc+addi, and lga uses auipc+ld
from the GOT.
lga does not allow an offset. If you try to use one, it will assemble
without error, but fail at link time with
(.text+0x10): dangerous relocation: The addend isn't allowed for R_RISCV_GOT_HI20
For now, just add a check for this. A proper fix involves some
changes to rv64/isel like is done for amd64.
when applying a custom set of CFLAGS under clang that does not include
-std=c99, asm is treated as a keyword and as such can not be used as an
identifier. this prevents the issue by renaming the offending variables.
Support "file" and "loc" directives. "file" takes a string (a file name)
assigns it a number, sets the current file to that number and records
the string for later. "loc" takes a single number and outputs location
information with a reference to the current file.
It is handy to express when
the end of a block cannot be
reached. If a hlt terminator
is executed, it traps the
program.
We don't go the llvm way and
specify execution semantics as
undefined behavior.
Symbols are a useful abstraction
that occurs in both Con and Alias.
In this patch they get their own
struct. This new struct packages
a symbol name and a type; the type
tells us where the symbol name
must be interpreted (currently, in
gobal memory or in thread-local
storage).
The refactor fixed a bug in
addcon(), proving the value of
packaging symbol names with their
type.
apple support is more than assembly syntax
in case of arm64 machines, and apple syntax
is currently useless in all cases but amd64;
rather than having a -G option that only
makes sense with amd64, we add a new target
amd64_apple
It is mostly complete, but still has a few ABI bugs when passing
floats in structs, or when structs are passed partly in register,
and partly on stack.
