This elides initialization for zero-sized arrays:
* for zero-sized elements we previously emitted an empty loop
* for arrays with a length of zero we previously emitted a loop with zero
iterations
This emits llvm.memset() instead of a loop over each element when:
* all elements are zero integers
* elements are byte sized
Translate array drop glue using MIR
I was a bit lazy here and used a usize-based index instead of a pointer iteration. Do you think this is important @eddyb?
r? @eddyb
Operand: 72 -> 24 B
Statement: 192 -> 96 B
Terminator: 256 -> 112 B
librustc translation memory usage: 1795 -> 1669 MB
next step would be interning lvalues, I suppose?
The main changes around rustc::ty::Layout::struct and rustc_trans:adt:
* Added primitive_align field which stores alignment before repr align
* Always emit field padding when generating the LLVM struct fields
* Added methods for adjusting field indexes from the layout index to the
LLVM struct field index
The main user of this information is rustc_trans::adt::struct_llfields
which determines the LLVM fields to be used by LLVM, including padding
fields.
Drop of arrays is now translated in trans::block in an ugly way that I
should clean up in a later PR, and does not handle panics in the middle
of an array drop, but this commit & PR are growing too big.
These changes are in the same commit to avoid needing to adapt
meth::trans_object_shim to the new scheme.
One codegen-units test is broken because we instantiate the shims even
when they are not needed. This will be fixed in the next PR.
According to the LLVM reference:
> A value of 0 or an omitted align argument means that the operation has
the ABI alignment for the target.
So loads/stores of fields of packed structs need to have their align set
to 1. Implement that by tracking the alignment of `LvalueRef`s.
Fixes#39376.
Fix transmute::<T, U> where T requires a bigger alignment than U
For transmute::<T, U> we simply pointercast the destination from a U
pointer to a T pointer, without providing any alignment information,
thus LLVM assumes that the destination is aligned to hold a value of
type T, which is not necessarily true. This can lead to LLVM emitting
machine instructions that assume said alignment, and thus cause aborts.
To fix this, we need to provide the actual alignment to store_operand()
and in turn to store() so they can set the proper alignment information
on the stores and LLVM can emit the proper machine instructions.
Fixes#32947
For transmute::<T, U> we simply pointercast the destination from a U
pointer to a T pointer, without providing any alignment information,
thus LLVM assumes that the destination is aligned to hold a value of
type T, which is not necessarily true. This can lead to LLVM emitting
machine instructions that assume said alignment, and thus cause aborts.
To fix this, we need to provide the actual alignment to store_operand()
and in turn to store() so they can set the proper alignment information
on the stores and LLVM can emit the proper machine instructions.
Fixes#32947
This commit introduces 128-bit integers. Stage 2 builds and produces a working compiler which
understands and supports 128-bit integers throughout.
The general strategy used is to have rustc_i128 module which provides aliases for iu128, equal to
iu64 in stage9 and iu128 later. Since nowhere in rustc we rely on large numbers being supported,
this strategy is good enough to get past the first bootstrap stages to end up with a fully working
128-bit capable compiler.
In order for this strategy to work, number of locations had to be changed to use associated
max_value/min_value instead of MAX/MIN constants as well as the min_value (or was it max_value?)
had to be changed to use xor instead of shift so both 64-bit and 128-bit based consteval works
(former not necessarily producing the right results in stage1).
This commit includes manual merge conflict resolution changes from a rebase by @est31.
