For now, this is just an extra flag that can be used to print stack
frame information, but this is intended to provide a way to determine
stack sizes for goroutines at compile time in many cases.
Stack sizes are often somewhere around 350 bytes so are in fact not all
that big usually. Once this can be determined at compile time in many
cases, it is possible to use this information when available and as a
result increase the fallback stack size if the size cannot be determined
at compile time. This should reduce stack overflows while at the same
time reducing RAM consumption in many cases.
Interesting output for testdata/channel.go:
function stack usage (in bytes)
Reset_Handler 332
.Lcommand-line-arguments.fastreceiver 220
.Lcommand-line-arguments.fastsender 192
.Lcommand-line-arguments.iterator 192
.Lcommand-line-arguments.main$1 184
.Lcommand-line-arguments.main$2 200
.Lcommand-line-arguments.main$3 200
.Lcommand-line-arguments.main$4 328
.Lcommand-line-arguments.receive 176
.Lcommand-line-arguments.selectDeadlock 72
.Lcommand-line-arguments.selectNoOp 72
.Lcommand-line-arguments.send 184
.Lcommand-line-arguments.sendComplex 192
.Lcommand-line-arguments.sender 192
.Lruntime.run$1 548
This shows that the stack size (if these numbers are correct) can in
fact be determined automatically in many cases, especially for small
goroutines. One of the great things about Go is lightweight goroutines,
and reducing stack sizes is very important to make goroutines
lightweight on microcontrollers.
Previously, the RAM was set to start at address 0. This is incorrect: on
AVR, the first few addresses are taken up by memory-mapped I/O. The
reason this didn't lead to problems (yet) was because the stack was
usually big enough to avoid real problems.
This commit adds support for software vectoring in the PLIC interrupt.
The interrupt table is created by the compiler, which leads to very
compact code while retaining the flexibility that the interrupt API
provides.
This commit lets the compiler know about interrupts and allows
optimizations to be performed based on that: interrupts are eliminated
when they appear to be unused in a program. This is done with a new
pseudo-call (runtime/interrupt.New) that is treated specially by the
compiler.
This simplifies the code. The fields are blank anyway so there is no way
to access them anyway (volatile or not).
Also do some other related simplifications of the code that result from
this change.
This should make it more maintainable. Another big advantage that
generation time (including gofmt) is now 3 times faster. No real attempt
at refactoring has been made, that will need to be done at a later time.
This brings a big speedup. Not counting gofmt time,
`make gen-device-avr` became about 3x faster. In the future, it might be
an idea to generate the AST in-memory and write it out already
formatted.
xml.etree.ElementTree is much easier to work with. This also fixes a few
small bugs in the parser. And as an added bonus, device generation got a
lot faster: apprently etree is a lot faster than minidom.
This is one step towards removing unnecessary special casts in most
cases. It is also part of removing as much magic as possible from the
compiler (the pragma is explicit, the special name is not).
