Internships/ProjectIdeas/TCGCodeQuality

Measure Tiny Code Generation Quality

Status: Vanderson M. do Rosario is working on this project for GSoC.

Project Github: vandersonmr/gsoc-qemu [1]

Summary: Improve the diagnostics tools to asses code quality

Improving the code generation of the TCG backend is a hard task that involves reading through large amounts of text looking for anomalies in the generated code. It would be nice to have tools to more readily extract and parse code generation information. This would include:

Modifying code generator, dumping additional data

• which are hot blocks (frequently run, hence more important performance wise)
• export block JIT information for perf tool (the later version)

Tweaking -d op,out_asm output

• how many fills/spills in a block (where register contents are moved due to register pressure)
• number of host instructions for each guest instruction (JIT profiling has a basic version of this)
• elide or beautify common blocks like softmmu access macros (which are always the same)

Modifying the HMP

• support interactive exploration of translation state (system emulation)

QEMU currently only works on translating simple basic blocks with one or two exit paths. This work could be a pre-cursor to supporting Internships/ProjectIdeas/Multi-exit Hot Blocks in the future.

Links:

• Documentation/TCG
• Hacky PoC of interactive translate info [2]

Details:

• Skill level: intermediate or advanced, understanding of code generation (compilers/JITs)
• Language: C, Assembly (x86 or preferred host)
• Mentor: Alex Bennée <alex.bennee@linaro.org> (stsquad on #qemu IRC)
• Suggested by: Alex Bennée