cranelift meeting notes for 6-6-22 (#4235)

meetings/cranelift/2022/cranelift-06-06.md

@@ -17,4 +17,69 @@
 
 ### Attendees
 
+- abrown
+- akirilov
+- avanhattum
+- cfallin
+- fitzgen
+- sparkerhaynes
+
 ### Notes
+
+- ISLE porting status and plans?
+  - abrown: Quarterly goals at Intel, port a number of instructions over to ISLE.
+    - Want to continue doing so.
+    - Issue is that all the hard ones are left.
+    - We need more people to look at it.
+  - akirilov: Quarterly basis too.
+    - Our approach was different, we've gone for the harder ones first.
+    - Trying to improve test coverage.
+  - abrown: How are you guys tracking coverage?
+  - akirilov: It's just manual, the bar is currently quite low so easy to see where they're missing.
+    - Interpreter has failed to handle some cases, something to do with splat.
+    - Some run tests don't check the return values.
+    - Sometimes disabling the interpreter tests.
+  - cfallin:  Sounds like the right approach.
+  - abrown: What's the state of SIMD interpreter support? afonso was working on it.
+  - cfallin: Don't know what happened to afonso, work has stalled on it.
+
+- akirilov: Regalloc2 limitation of only 2 reg classes
+  - SVE will need a predicate file, same for AVX-512.
+- cfallin: Bit packing issue, could remove the 'mod' operands and reuse that bit.
+- akirilov: Will four classes be enough..? It is probably fine for AArch64.
+- cfallin: Will keep this on my back burner.
+
+# standups
+
+- fitzgen: No updates.
+
+- avanhattum: Better semantics for verification.
+  - SAIL for x64 and arm.
+  - Figuring out what work is needed to use modern SAIL for x64.
+  - Working on shim code to avoid annoting machine instructions.
+
+- akirilov: cranelift CFI patch updates and Fiber changes for MacOS.
+  - bjorn3 gave feedback and noticed codegen wasn't right.
+  - some branches were elided and the branch target instructions ended up as the last instruction, not first.
+  - pointer authentication is still disabled in qemu.
+
+- cfallin: Implemented alias analysis for load elimination, with okay speedups.
+  - could have benefitted some option optimizations, such as GVN
+  - So developing a unified framework for rewrite rules in the mid-end.
+  - egraphs seem the right approach.
+  - need an adapter to convert the egraph to LowerCtx: clif -> egraph -> vcode
+  - Then need to figure out isle rewrite rules.
+  - Framework will subsume all the existing mid-end optimisations.
+  - Also worked on a fix regalloc2 issue, reducing stack size usage.
+    - alexa: static rewrite rules or equality saturation?
+    - chris: equality.
+
+- abrown: shared memory in wasmtime.
+  - impacts cranelift through `memory_size` instruction.
+  - How are we gonna test this? Looking for ideas and feedback.
+  - Ported some atomic operations for x64, not sure CAS is right.
+
+- sparker: Dynamic vector RFC is up in code form.
+  - It's a bit rough and would greatly appreciate some feedback.
+    - cfallin: does qemu support sve?
+    - sparker: yes.