cmd/compile: infinite loop in compiler

[randall77]

git clone https://github.com/valkey-io/valkey-go
cd valkey-go/internal/cmds
go test -c

Seems to generate an infinite loop in the compiler. Probably in this vicinity:

  thread #23
    frame #0: 0x00000001007dacc4 compile`runtime.scanObject + 308
    frame #1: 0x00000001007d9e3c compile`runtime.gcDrainN + 444
    frame #2: 0x00000001007d7f08 compile`runtime.gcAssistAlloc1 + 280
    frame #3: 0x00000001007d7d70 compile`runtime.gcAssistAlloc.func2 + 32
    frame #4: 0x0000000100834a98 compile`runtime.systemstack.abi0 + 104
    frame #5: 0x00000001007d79f4 compile`runtime.gcAssistAlloc + 772
    frame #6: 0x00000001007c8894 compile`runtime.deductAssistCredit + 68
    frame #7: 0x000000010082c3bc compile`runtime.mallocgc + 92
    frame #8: 0x00000001008312c0 compile`runtime.makeslice + 80
    frame #9: 0x0000000100b3c1f0 compile`cmd/compile/internal/ssa.(*poset).dfs + 128
    frame #10: 0x0000000100b3cc10 compile`cmd/compile/internal/ssa.(*poset).findroot + 128
    frame #11: 0x0000000100b3f9a4 compile`cmd/compile/internal/ssa.(*poset).setOrder + 804
    frame #12: 0x0000000100b406e8 compile`cmd/compile/internal/ssa.(*poset).SetOrder + 104
    frame #13: 0x0000000100b45b14 compile`cmd/compile/internal/ssa.(*factsTable).update + 596
    frame #14: 0x0000000100b4c4b8 compile`cmd/compile/internal/ssa.addLocalFacts + 712
    frame #15: 0x0000000100b493ec compile`cmd/compile/internal/ssa.prove + 4924
    frame #16: 0x0000000100af17dc compile`cmd/compile/internal/ssa.Compile + 2732
    frame #17: 0x0000000100e40480 compile`cmd/compile/internal/ssagen.buildssa + 9344
    frame #18: 0x0000000100e38670 compile`cmd/compile/internal/ssagen.Compile + 112
    frame #19: 0x0000000101000168 compile`cmd/compile/internal/gc.compileFunctions.func5.1 + 56
    frame #20: 0x0000000101000564 compile`cmd/compile/internal/gc.compileFunctions.func3.1 + 52

Probably caused (or at least, triggered) by CL 679155.
@DanielMorsing

[gabyhelp]

Related Issues

• cmd/compile: infinite loop in the inliner #73425 (closed)
• cmd/compile: infinite loop in types2 #48136 (closed)
• cmd/compile: panic while compiling empty package in a loop #16726 (closed)
• cmd/compile: infinite loop #48135 (closed)
• cmd/compile: infinite loop in -G=3 type instantiation #48030 (closed)
• cmd/compile: regression in writebarrier pass #19179 (closed)
• cmd/gc: hangs infinitely during compilation #8076 (closed)
• cmd/compile: crash in regalloc #15585 (closed)
• cmd/compile/internal/SSA: panic in Compile on linux-amd64-noopt #54906 (closed)
• cmd/compile: := assignment in for loop statement throws internal compiler error #20840 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[randall77]

The loop may not be infinite. But the function is really big; I'm seeing SSA value IDs north of 250,000. It may just be something quadratic is rearing its ugly head.

[fengyoulin]

Probably caused (or at least, triggered) by CL 679155.

I tested and found that this CL made the compiler performance worse.

git clone https://github.com/valkey-io/valkey-go
cd valkey-go/internal/cmds
go test -c

Both 1.25rc3 and 1.24.6 can finish within one minute. But the HEAD ran out of memory in my WSL2 environment and eventually OOM.

[DanielMorsing]

I wrote CL 679155 to prepare for a larger change that I don't think is the way forward any more. I'm happy with a revert.

[gopherbot]

Change https://go.dev/cl/695175 mentions this issue: Revert "cmd/compile/internal/ssa: Use transitive properties for len/cap"

[randall77]

Closing, as the revert is in.