[Bug middle-end/67341] New: [ICE] libgo build failure: in mark_stmt_if_obviously_necessary, at tree-ssa-dce.c:278

[gary at intrepid dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67341

            Bug ID: 67341
           Summary: [ICE] libgo build failure: in
                    mark_stmt_if_obviously_necessary, at
                    tree-ssa-dce.c:278
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gary at intrepid dot com
  Target Milestone: ---

A change made to the trunk within the past week/so (trunk version greater than
227110) triggers this ICE.  Full bootstrap, release checks, CFLAGS='-O3'.

libtool: compile:  /eng/upc/dev/gary/gupc-merge/bld/packed-opt/./gcc/gccgo
-B/eng/upc/dev/gary/gu
pc-merge/bld/packed-opt/./gcc/
-B/eng/upc/dev/gary/gupc-merge/rls/packed-opt/x86_64-pc-linux-gnu/
bin/ -B/eng/upc/dev/gary/gupc-merge/rls/packed-opt/x86_64-pc-linux-gnu/lib/
-isystem /eng/upc/dev
/gary/gupc-merge/rls/packed-opt/x86_64-pc-linux-gnu/include -isystem
/eng/upc/dev/gary/gupc-merge
/rls/packed-opt/x86_64-pc-linux-gnu/sys-include -minline-all-stringops -O2 -g
-I . -c -fgo-pkgpat
h=encoding/gob
/eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/decode.go
/eng/upc/dev
/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/decoder.go
/eng/upc/dev/gary/gupc-merge/src/gupc/
libgo/go/encoding/gob/dec_helpers.go
/eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/
doc.go /eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/encode.go
/eng/upc/dev/gary/gu
pc-merge/src/gupc/libgo/go/encoding/gob/encoder.go
/eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go
/encoding/gob/enc_helpers.go
/eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/error.go
 /eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/type.go  -fPIC -o
encoding/.libs/gob
.o
/eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/decode.go: In
function ‘gob.decIgnoreOpFor.pN20_encoding_gob.Decoder’:
/eng/upc/dev/gary/gupc-merge/src/gupc/libgo/go/encoding/gob/decode.go:843:1:
internal compiler error: in mark_stmt_if_obviously_necessary, at
tree-ssa-dce.c:278
 func (dec *Decoder) decIgnoreOpFor(wireId typeId) decOp {
 ^
0xa80fab mark_stmt_if_obviously_necessary
        /eng/upc/dev/gary/gupc-merge/src/gupc/gcc/tree-ssa-dce.c:278
0xa80fab find_obviously_necessary_stmts
        /eng/upc/dev/gary/gupc-merge/src/gupc/gcc/tree-ssa-dce.c:397
0xa80fab perform_tree_ssa_dce
        /eng/upc/dev/gary/gupc-merge/src/gupc/gcc/tree-ssa-dce.c:1635