If we're loading a constant value, print the constant (and the zero upper elements) instead of just the shuffle mask.
This did require me to move the shuffle mask handling into addConstantComments as we can't handle this in the MC layer.
If we are loading the same ptr at different vector widths, then reuse the largest load and just extract the low subvector.
Unlike the equivalent VBROADCAST_LOAD/SUBV_BROADCAST_LOAD folds which can occur in DAG, we have to wait until DAGISel otherwise we can hit infinite loops if constant folding recreates the original constant value.
This is mainly useful for better constant sharing.
If we are loading the same ptr at different vector widths, then reuse the larger load and just extract the low subvector.
Unlike the equivalent VBROADCAST_LOAD/SUBV_BROADCAST_LOAD folds which can occur in DAG, we have to wait until DAGISel otherwise we can hit infinite loops if constant folding recreates the original constant value.
This is mainly useful for better constant sharing.
PR #66334 tried to renumber slot indexes before register allocation, but
the numbering was still affected by list entries for instructions which
had been erased. Fix this to make the register allocator's live range
length heuristics even less dependent on the history of how instructions
have been added to and removed from SlotIndexes's maps.
Fixes root cause of #63017.
The reason is similar to BUILD_VECTOR. We have legal vector type but
still soft promote for scalar type. So we need to customize these scalar
to vector nodes.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D155961
This is an alternative of D120395 and D120411.
Previously we use `__bfloat16` as a typedef of `unsigned short`. The
name may give user an impression it is a brand new type to represent
BF16. So that they may use it in arithmetic operations and we don't have
a good way to block it.
To solve the problem, we introduced `__bf16` to X86 psABI and landed the
support in Clang by D130964. Now we can solve the problem by switching
intrinsics to the new type.
Reviewed By: LuoYuanke, RKSimon
Differential Revision: https://reviews.llvm.org/D132329
This stops reporting CostPerUse 1 for `R8`-`R15` and `XMM8`-`XMM31`.
This was previously done because instruction encoding require a REX
prefix when using them resulting in longer instruction encodings. I
found that this regresses the quality of the register allocation as the
costs impose an ordering on eviction candidates. I also feel that there
is a bit of an impedance mismatch as the actual costs occure when
encoding instructions using those registers, but the order of VReg
assignments is not primarily ordered by number of Defs+Uses.
I did extensive measurements with the llvm-test-suite wiht SPEC2006 +
SPEC2017 included, internal services showed similar patterns. Generally
there are a log of improvements but also a lot of regression. But on
average the allocation quality seems to improve at a small code size
regression.
Results for measuring static and dynamic instruction counts:
Dynamic Counts (scaled by execution frequency) / Optimization Remarks:
Spills+FoldedSpills -5.6%
Reloads+FoldedReloads -4.2%
Copies -0.1%
Static / LLVM Statistics:
regalloc.NumSpills mean -1.6%, geomean -2.8%
regalloc.NumReloads mean -1.7%, geomean -3.1%
size..text mean +0.4%, geomean +0.4%
Static / LLVM Statistics:
mean -2.2%, geomean -3.1%) regalloc.NumSpills
mean -2.6%, geomean -3.9%) regalloc.NumReloads
mean +0.6%, geomean +0.6%) size..text
Static / LLVM Statistics:
regalloc.NumSpills mean -3.0%
regalloc.NumReloads mean -3.3%
size..text mean +0.3%, geomean +0.3%
Differential Revision: https://reviews.llvm.org/D133902
The main difference is that this preserves intermediate rounding steps,
which the other route doesn't. This aligns bfloat16 more with half
floats, which use this path on most targets.
I didn't understand what the difference was between these softening
approaches when I first added bfloat lowerings, would be nice if we only
had one of them.
Based on @pengfei 's D131502
Differential Revision: https://reviews.llvm.org/D133207
This is modeled after the half-precision fp support. Two new nodes are
introduced for casting from and to bf16. Since casting from bf16 is a
simple operation I opted to always directly lower it to integer
arithmetic. The other way round is more complicated if you want to
preserve IEEE semantics, so it's handled by a new __truncsfbf2
compiler-rt builtin.
This is of course very bare bones, but sufficient to get a semi-softened
fadd on x86.
Possible future improvements:
- Targets with bf16 conversion instructions can now make fp_to_bf16 legal
- The software conversion to bf16 can be replaced by a trivial
implementation under fast math.
Differential Revision: https://reviews.llvm.org/D126953
