A CallConv enum on every function signature makes it possible to
generate calls to functions with different calling conventions within
the same ISA / within a single function.
The calling conventions also serve as a way of customizing Cretonne's
behavior when embedded inside a VM. As an example, the SpiderWASM
calling convention is used to compile WebAssembly functions that run
inside the SpiderMonkey virtual machine.
All function signatures must have a calling convention at the end, so
this changes the textual IL syntax.
Before:
sig1 = signature(i32, f64) -> f64
After
sig1 = (i32, f64) -> f64 native
sig2 = (i32) spiderwasm
When printing functions, the signature goes after the return types:
function %r1() -> i32, f32 spiderwasm {
ebb1:
...
}
In the parser, this calling convention is optional and defaults to
"native". This is mostly to avoid updating all the existing test cases
under filetests/. When printing a function, the calling convention is
always included, including for "native" functions.
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