Stream: git-wasmtime

Topic: wasmtime / PR #6874 cranelift: Remove `f{min,max}_pseudo`...

Wasmtime GitHub notifications bot (Aug 21 2023 at 20:06):

alexcrichton opened PR #6874 from alexcrichton:remove-fmin-max-pseudo to bytecodealliance:main:

This commit removes these two instructions and replaces them instead with their equivalents using fcmp plus select or bitselect depending on the type (bitselect for vectors, select for scalars). The motivation for this commit is that incorrect optimizations for these instructions were removed in #6859 and likely stemmed from the surprising definitions of these instructions. These originally were intended to correspond to operations in the SIMD proposal for WebAssembly but nowadays the functionality of these instructions is replaced with:

• Lowering from wasm to clif uses the fcmp plus select combo instruction.
• Backends that support optimizing this pattern use ISLE patterns to match the instruction and emit the specialization for the pseudo semantics.

This means that while the instructions are removed here it should be the case that no functionality is lost and the output of Wasmtime/Cranelift should still be the same as it was before. Existing tests using the pseudo instructions were preserved except the riscv64 ones (where the lowering was deleted) and the dynamic AArch64 ones. Both s390x and x64 continue to have specialized patterns for this compare-plus-select.

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Wasmtime GitHub notifications bot (Aug 21 2023 at 20:06):

alexcrichton requested elliottt for a review on PR #6874.

Wasmtime GitHub notifications bot (Aug 21 2023 at 20:06):

alexcrichton requested wasmtime-compiler-reviewers for a review on PR #6874.

Wasmtime GitHub notifications bot (Aug 21 2023 at 20:13):

fitzgen submitted PR review:

Nice!

Wasmtime GitHub notifications bot (Aug 21 2023 at 20:13):

fitzgen has enabled auto merge for PR #6874.

Wasmtime GitHub notifications bot (Aug 21 2023 at 21:27):

fitzgen merged PR #6874.

Last updated: Dec 23 2024 at 12:05 UTC