cmd/compile: failure to run `make.bash` with `GOEXPERIMENT=greenteagc` on loong64

[mknyszek]

There's a compiler panic that happens on one of the new functions. Looks like a compiler bug?

runtime/mgcmark_greenteagc.go:778:30: internal compiler error: '(*gcWork).tryStealSpan': panic during regalloc while compiling (*gcWork).tryStealSpan:

runtime error: invalid memory address or nil pointer dereference

goroutine 3846 [running]:
cmd/compile/internal/ssa.Compile.func1()
	cmd/compile/internal/ssa/compile.go:49 +0x67
panic({0xe52ec0?, 0x166fa60?})
	runtime/panic.go:858 +0x13a
cmd/compile/internal/ssa.(*edgeState).processDest(0x3801c7a88de8, {0x1085860, 0x169d520}, 0x111, 0x0, {0xc6944708?, 0x3801?})
	cmd/compile/internal/ssa/regalloc.go:2508 +0x106
cmd/compile/internal/ssa.(*edgeState).process(0x3801c7a88de8)
	cmd/compile/internal/ssa/regalloc.go:2424 +0x10e
cmd/compile/internal/ssa.(*regAllocState).shuffle(0x3801c5ba0000, {0x3801c694c008, 0x2d, 0x2d?})
	cmd/compile/internal/ssa/regalloc.go:2303 +0x20d
cmd/compile/internal/ssa.(*regAllocState).regalloc(0x3801c5ba0000, 0x3801c647c4e0)
	cmd/compile/internal/ssa/regalloc.go:2124 +0x4694
cmd/compile/internal/ssa.regalloc(0x3801c647c4e0)
	cmd/compile/internal/ssa/regalloc.go:149 +0x3d
cmd/compile/internal/ssa.Compile(0x3801c647c4e0)
	cmd/compile/internal/ssa/compile.go:97 +0xbd9
cmd/compile/internal/ssagen.buildssa(0x3801c167bcc0, 0x2, 0x0)
	cmd/compile/internal/ssagen/ssa.go:573 +0x2e25
cmd/compile/internal/ssagen.Compile(0x3801c167bcc0, 0x2, 0x0?)
	cmd/compile/internal/ssagen/pgen.go:304 +0x88
cmd/compile/internal/gc.compileFunctions.func5.1(0x0?)
	cmd/compile/internal/gc/compile.go:191 +0x38
cmd/compile/internal/gc.compileFunctions.func3.1()
	cmd/compile/internal/gc/compile.go:173 +0x30
created by cmd/compile/internal/gc.compileFunctions.func3 in goroutine 192
	cmd/compile/internal/gc/compile.go:172 +0x33e

https://logs.chromium.org/logs/golang/buildbucket/cr-buildbucket/8701732835052710833/+/u/step/15/log/2

CC @golang/loong64

[mknyszek]

I'm in the process of turning Green Tea on by default, but I'm going to disable it on loong64 to begin with due to this problem. Once this is fixed, please enable it by default so we can shake out any more latent issues.

[gabyhelp]

Related Issues

• cmd/compile: internal compiler error: panic during lower in linux/loong64 #53018 (closed)
• cmd/compile/internal/SSA: panic in Compile on linux-amd64-noopt #54906 (closed)
• runtime: crash on `linux-riscv64-jsing` during bootstrap #53721
• cmd/compile: panic during early copyelim crash #35658 (closed)
• cmd/compile: internal compiler error: panic during lower (unreachable) on arm64 #30679 (closed)
• cmd/compile: internal compiler error: panic during lower #29215 (closed)
• cmd/compile/internal/gc: panic in buildssa #41077 (closed)
• cmd/compile: make.bash with GOAMD64=v3 broken by CL 354670 #49061 (closed)
• runtime: 'unexpected fault address 0x0' in evacuate_fast32 on linux-mips64le-mengzhuo builder #34835
• cmd/compile: panic: runtime error: invalid memory address or nil pointer dereference [dev.regabi] #43701 (closed)

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

[xen0n]

Reverting https://go.dev/cl/696035 made the ICE go away and all tests passed with greenteagc enabled, but I still haven't pinpointed what's wrong with loong64's regalloc behavior.