These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild     U  ] sys-apps/kmod-26-r3::gentoo [26-r2::gentoo] USE="tools zlib -debug -doc -libressl -lzma -pkcs7% -python -static-libs (-ssl%*)" PYTHON_TARGETS="python2_7 python3_6 -python3_5 (-python3_7)" 0 KiB
[ebuild     U  ] sys-apps/acl-2.2.53::gentoo [2.2.52-r1::gentoo] USE="nls (split-usr) -static-libs" ABI_X86="(64) -32 (-x32)" 513 KiB
[ebuild     U  ] media-libs/flac-1.3.3::gentoo [1.3.2-r1::gentoo] USE="cxx ogg (-altivec) -debug -static-libs" ABI_X86="(64) -32 (-x32)" CPU_FLAGS_X86="-sse" 1,020 KiB
[ebuild     U  ] app-eselect/eselect-blas-0.2::gentoo [0.1::gentoo] 0 KiB
[ebuild     U  ] x11-libs/libnotify-0.7.8::gentoo [0.7.7-r1::gentoo] USE="introspection -test" ABI_X86="(64) -32 (-x32)" 106 KiB
[ebuild  N     ] sci-libs/lapack-3.8.0::gentoo  USE="-doc -eselect-ldso -lapacke" 7,253 KiB
[uninstall     ] sci-libs/lapack-reference-3.2.1-r4::gentoo  USE="-doc"
[blocks b      ] sci-libs/lapack-reference ("sci-libs/lapack-reference" is blocking sci-libs/lapack-3.8.0)
[ebuild     U  ] virtual/blas-3.8::gentoo [3.7::gentoo] USE="-eselect-ldso%" 0 KiB
[ebuild     U  ] virtual/lapack-3.8::gentoo [3.1::gentoo] USE="-eselect-ldso%" 0 KiB
[blocks B      ] sci-libs/cblas-reference ("sci-libs/cblas-reference" is blocking sci-libs/lapack-3.8.0)
[blocks B      ] app-eselect/eselect-cblas ("app-eselect/eselect-cblas" is blocking sci-libs/lapack-3.8.0)
[blocks B      ] sci-libs/blas-reference ("sci-libs/blas-reference" is blocking sci-libs/lapack-3.8.0)

Total: 8 packages (7 upgrades, 1 new, 1 uninstall), Size of downloads: 8,890 KiB
Conflict: 4 blocks (3 unsatisfied)

 * Error: The above package list contains packages which cannot be
 * installed at the same time on the same system.

  (sci-libs/cblas-reference-20030223-r6:0/0::gentoo, installed) pulled in by
    sci-libs/cblas-reference required by @selected
    sci-libs/cblas-reference required by (virtual/cblas-1.0:0/0::gentoo, installed)

  (sci-libs/lapack-3.8.0:0/0::gentoo, ebuild scheduled for merge) pulled in by
    >=sci-libs/lapack-3.8[eselect-ldso?] (>=sci-libs/lapack-3.8) required by (virtual/blas-3.8:0/0::gentoo, ebuild scheduled for merge)
    >=sci-libs/lapack-3.8.0[eselect-ldso?] (>=sci-libs/lapack-3.8.0) required by (virtual/lapack-3.8:0/0::gentoo, ebuild scheduled for merge)

  (app-eselect/eselect-cblas-0.1:0/0::gentoo, installed) pulled in by
    app-eselect/eselect-cblas required by @selected
    app-eselect/eselect-cblas required by (sci-libs/cblas-reference-20030223-r6:0/0::gentoo, installed)

  (sci-libs/blas-reference-20161223:0/0::gentoo, installed) pulled in by
    sci-libs/blas-reference required by @selected