Florian Hahn 078d214672
[TailDup] Delay aggressive computed-goto taildup to after RegAlloc. (#150911)
https://github.com/llvm/llvm-project/pull/114990 allowed more aggressive
tail duplication for computed-gotos in both pre- and post-regalloc tail
duplication.

In some cases, performing tail-duplication too early can lead to worse
results, especially if we duplicate blocks with a number of phi nodes.

This is causing a ~3% performance regression in some workloads using
Python 3.12.

This patch updates TailDup to delay aggressive tail-duplication for
computed gotos to after register allocation.

This means we can keep the non-duplicated version for a bit longer
throughout the backend, which should reduce compile-time as well as
allowing a number of optimizations and simplifications to trigger before
drastically expanding the CFG.

For the case in https://github.com/llvm/llvm-project/issues/106846, I
get the same performance with and without this patch on Skylake.

PR: https://github.com/llvm/llvm-project/pull/150911
2025-07-31 19:20:05 +01:00
..
2025-03-30 16:38:16 -07:00

++ SVE CodeGen Warnings ++

When the WARN check lines fail in the SVE codegen tests it most likely means you
have introduced a warning due to:
1. Adding an invalid call to VectorType::getNumElements() or EVT::getVectorNumElements()
   when the type is a scalable vector.
2. Relying upon an implicit cast conversion from TypeSize to uint64_t.

For generic code, please modify your code to work with ElementCount and TypeSize directly.
For target-specific code that only deals with fixed-width vectors, use the fixed-size interfaces.
Please refer to the code where those functions live for more details.