gccgo: internal compiler error: Segmentation fault during GIMPLE pass: ealias

[ALTree]

$ gccgo --version
gccgo (Debian 10.2.1-6) 10.2.1 20210110

package main

func main() {
	var b1, b2 byte
	f := func() int {
		var m map[byte]int
		return m[b1/b2]
	}
	f()
}

$ gccgo -O2 crash.go 

during GIMPLE pass: ealias
In function ‘main.main..func1’:
go1: internal compiler error: Segmentation fault
0x7f5b4b547d5f ???
	./signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
0x7f5b4b532d09 __libc_start_main
	../csu/libc-start.c:308
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-10/README.Bugs> for instructions.

cc @ianlancetaylor @thanm

[thanm]

Looks to be reproduceable on tip:

$ gccgo -O2 -c crash.go
In function ‘main.main..func1’:
go1: error: definition in block 3 does not dominate use in block 9
for SSA_NAME: _3 in statement:
# VUSE <.MEM_13(D)>
_18 = *_3;
during GIMPLE pass: ssa
go1: internal compiler error: verify_ssa failed
0x1081a31 verify_ssa(bool, bool)
	../../gcc-trunk/gcc/tree-ssa.c:1214
0xd8be95 execute_function_todo
	../../gcc-trunk/gcc/passes.c:2049
0xd8cbdc do_per_function
	../../gcc-trunk/gcc/passes.c:1687
0xd8cbdc execute_todo
	../../gcc-trunk/gcc/passes.c:2096

[gopherbot]

Change https://golang.org/cl/300789 mentions this issue: test: add test that caused a gofrontend internal error

[gopherbot]

Change https://golang.org/cl/300809 mentions this issue: compiler: create temporaries for heap variables