Stream: git-wasmtime

Topic: wasmtime / PR #2195 machinst x64: two optimizations

Wasmtime GitHub notifications bot (Sep 11 2020 at 16:01):

bnjbvr edited PR #2195 from x64-refactor to main:

• First optimization matches addresses of the form base+index+offset, where index is a constant, and tries to add the constant with offset. This has been proven useful for some temporary variables computations in Spidermonkey (e.g. address of global values).
• Second optimization regenerates constants in new vregs in put_input_to_reg, minimizing their live ranges.

There are a few bonus pieces here and there:

• fix a few places where regenerating constants would clobber the flags (b/o xor for 0 constants), by reordering calls to put_input_in_reg so they're before the comparison emission.
• fix the generation of R64 constants
• use a mov imm32 sign-extended to reg, whenever possible, when generating an i64 immediate.

See also commit details.

This is up to a 17% speedup in compile times of the embenchen micro benchmarks, and up to 10% reduction in runtime speed.

Wasmtime GitHub notifications bot (Sep 11 2020 at 16:13):

bnjbvr updated PR #2195 from x64-refactor to main:

• First optimization matches addresses of the form base+index+offset, where index is a constant, and tries to add the constant with offset. This has been proven useful for some temporary variables computations in Spidermonkey (e.g. address of global values).
• Second optimization regenerates constants in new vregs in put_input_to_reg, minimizing their live ranges.

There are a few bonus pieces here and there:

• fix a few places where regenerating constants would clobber the flags (b/o xor for 0 constants), by reordering calls to put_input_in_reg so they're before the comparison emission.
• fix the generation of R64 constants
• use a mov imm32 sign-extended to reg, whenever possible, when generating an i64 immediate.

See also commit details.

This is up to a 17% speedup in compile times of the embenchen micro benchmarks, and up to 10% reduction in runtime speed.

Wasmtime GitHub notifications bot (Sep 11 2020 at 18:21):

cfallin submitted PR Review.

Wasmtime GitHub notifications bot (Sep 11 2020 at 18:21):

cfallin merged PR #2195.

Last updated: Dec 13 2025 at 19:03 UTC