Functions are now aligned on 16-byte
boundaries. This mimics gcc and should
help reduce the maximum perf impact of
cosmetic code changes. Previously, any
change in the output of qbe could have
far reaching implications on alignment.
Thanks to Roland Paterson-Jones for
pointing out the variability issue.
This significantly improves parsing performance for massive functions
with a huge number of temporaries. Parsing the 86MiB IL produced
by cproc during zig bootstrap drops from 17m15s to 2.5s (over 400x
speedup).
The speedup is much smaller for IL produced from normal non-autogenerated
C code. Parsing the sqlite3 amalgamation drops from 0.40s to 0.33s.
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.
Crashing loads of uninitialized memory
proved to be a problem when implementing
unions using qbe. This patch introduces
a new UNDEF Ref to represent data that is
known to be uninitialized. Optimization
passes can make use of it to eliminate
some code. In the last compilation stages,
UNDEF is treated as the constant 0xdeaddead.
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.
When qbe is used with other tools is a bit hard to identify
what is the tool that is generating the error. Adding an
identifier at the beginning of the line makes much easier
to identify the tool generating the error.
The risc-v abi needs to know if a
type is defined as a union or not.
We cannot use nunion to obtain this
information because the risc-v abi
made the unfortunate decision of
treating
union { int i; }
differently from
int i;
So, instead, I introduce a single
bit flag 'isunion'.
parseref() has code to reuse address constants, but this is not
done in other passes such as fold or isel. Introduce a new function
newcon() which takes a Con and returns a Ref for that constant, and
use this whenever creating address constants.
This is necessary to fix folding of address constants when one
operand is already folded. For example, in
%a =l add $x, 1
%b =l add %a, 2
%c =w loadw %b
%a and %b were folded to $x+1 and $x+3 respectively, but then the
second add is visited again since it uses %a. This gets folded to
$x+3 as well, but as a new distinct constant. This results in %b
getting labeled as bottom instead of either constant, disabling the
replacement of %b by a constant in subsequent instructions (such
as the loadw).
Some abis, like the riscv one, treat
arguments differently depending on
whether they are variadic or not.
To prepare for the upcomming riscv
target, we change the variadic call
syntax and give meaning to the
location of the '...' marker.
# new syntax
%ret =w call $f(w %regular, ..., w %variadic)
By nature of their abis, the change
is backwards compatible for existing
targets.
The documentation states that loadw is syntactic sugar for loadsw,
but it actually got parsed as Oload. If the result is an l temporary,
Oload behaves like Oloadl, not Oloadsw.
To fix this, parse Tloadw as Oloadsw explicitly.
This was causing issues with aggregate types. A simple reproduction is:
type :type.1 = align 8 { 24 }
type :type.2 = align 8 { w 1, :type.1 1 }
The size of type.2 should be 32, adding only 4 bytes of padding between
the first and second field. Prior to this patch, 20 bytes of padding was
added instead, causing the type to have a size of 48.
Signed-off-by: Drew DeVault <sir@cmpwn.com>
This allows you to explicitly specify the section to emit the data
directive for, allowing for sections other than .data: for example, .bss
or .init_array.
