This implements the initial fptrunc instruction. For all other floating-point truncating,
a call to compiler-rt is required. (This also updates fpext to emit the same error).
- Implement switching over booleans and pointers.
- Fix sparse-detection where the lowest value was never truly set
as it started at a non-zero number and the case was > 50.
- Fix indexing the jump table by ensuring it starts indexing from 0.
This required adjusting `Type.nameAlloc` to be used with a
general-purpose allocator and added `Type.nameAllocArena` for the arena
use case (avoids allocation sometimes).
Previously, we did this so that we could insert a debug variable
declaration intrinsic on the alloca. But there is a dbg.value intrinsic
for declaring variables that are values.
The comment notes that we can't because of constness, but the recent
work by @Vexu lets us use the bitcast ty cause constness comes later.
The following tests pass from this:
```
test "A" {
const ary = [_:0]u8{42};
const ptr: [*:0]const u8 = &ary;
try expect(ptr[1] == 0);
}
test "B" {
comptime {
const ary = [_:0]u8{42};
const ptr: [*:0]const u8 = &ary;
try expect(ptr[1] == 0);
}
}
```
By the time zirElemVal is reached for a many pointer, a load has already
happened, making sure the operand is already dereferenced.
This makes `mem.sliceTo` now work.
This uses a new ZIR inst `array_init_sent` (and a ref equivalent) to
represent array init expressions that terminate in a a sentinel value.
The sentienl value is the last value in the `MultiOp` payload. This
makes it a bit more awkward to deal with (lots of "len - 1") but makes
it so that the payload matches the fact that sentinels appear at the end
of arrays. However, this is not a hill I want to die on so if we want to
change it to index 0, I'm happy to do so.
This makes the following work properly:
try expect(@TypeOf([_:0]u8{}) == [0:0]u8);
Array types with sentinels were not being typed correctly in the
translation from ZIR to Sema (comptime). This modifies the `array_init`
ZIR to also retain the type of the init expression (note: untyped array
initialization is done via the `array_init_anon` ZIR and so is unchanged
in this commit).
