cmd/compile: internal compiler error: arg 0 of value v4 = Load <int> v19 v8 does not dominate (with ssacheck)

[ALTree]

$ go version
go version go1.17 linux/amd64

$ gotip version
go version devel go1.18-6a35e07512 Fri Aug 27 16:41:29 2021 +0000 linux/amd64

package p

var i int

type t struct {
	a, b, c, d, e int
}

func f(p t, q int) int {
	var a, b, c, d, e, f, g int
	var h, i, j, k, l, m int
	_, _, _, _, _, _, _ = a, b, c, d, e, f, g
	_, _, _, _, _, _ = h, i, j, k, l, m
	return 0
}

func g() int {
	var v t
	return f(v, 1<<i)
}

$ go build -gcflags=-d=ssa/check/seed=1 crash.go

# command-line-arguments
./crash.go:19:14: internal compiler error: 'g': arg 0 of value v4 = Load <int> v20 v9 does not dominate, arg=v20 = OffPtr <*int> [8] v10

Please file a bug report including a short program that triggers the error.

Go 1.16 is not affected.

cc @randall77 @josharian

[randall77]

@dr2chase Looks like this is happening in expandCalls.

/Users/khr/gowork/issue48026.go:19:14: internal compiler error: 'g': arg 0 of value v4 = Load <int> v19 v8 does not dominate, arg=v19 = OffPtr <*int> [8] v9

b1:
   v4 (+19) = Load <int> v19 v8
   If v14 → b2 b3 (likely) (+19)
b2: ← b1
   v19 (19) = OffPtr <*int> [8] v9

The OffPtr was put in the block following the block of the Load that is using it.

[cuonglm]

The problem seems to be in storeOneLoad, we emit OffPtr in the input b, but the do the Load in source.Block.

[gopherbot]

Change https://golang.org/cl/345434 mentions this issue: cmd/compile: fix offset-generator for storeOneLoad