diff --git a/.travis.yml b/.travis.yml
index c1f9a626ae78..2e197b2c95ff 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,11 +1,12 @@
 language: d
 d:
   - dmd
-  - gdc
   - ldc
 
 script:
+  - DMD_BIN="$DMD"
   - deactivate # deactivate d compiler
+  - export DMD="$DMD_BIN"
   - ./travis.sh
 
 sudo: false
@@ -18,7 +19,6 @@ addons:
 
 env:
   - MODEL=32
-  - MODEL=64
 
 matrix:
   include:
diff --git a/README.md b/README.md
index b49ce515ec2d..f89f02f9e57f 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,9 @@ DMD
 [![Code coverage](https://img.shields.io/codecov/c/github/dlang/dmd.svg?maxAge=86400)](https://codecov.io/gh/dlang/dmd)
 [![license](https://img.shields.io/github/license/dlang/dmd.svg)](https://github.com/dlang/dmd/blob/master/LICENSE.txt)
 
+[![CircleCI](https://circleci.com/gh/dlang/dmd/tree/master.svg?style=svg)](https://circleci.com/gh/dlang/dmd/tree/master)
+[![Build Status](https://semaphoreci.com/api/v1/cybershadow/dmd/branches/master/badge.svg)](https://semaphoreci.com/cybershadow/dmd)
+
 DMD is the reference compiler for the D programming language.
 
 To report a problem or browse the list of open bugs, please visit the
diff --git a/ci.sh b/ci.sh
new file mode 100755
index 000000000000..590e9063a29c
--- /dev/null
+++ b/ci.sh
@@ -0,0 +1,154 @@
+#!/bin/bash
+
+set -uexo pipefail
+
+if [ -z ${N+x} ] ; then echo "Variable 'N' needs to be set."; exit 1; fi
+if [ -z ${BRANCH+x} ] ; then echo "Variable 'BRANCH' needs to be set."; exit 1; fi
+if [ -z ${OS_NAME+x} ] ; then echo "Variable 'OS_NAME' needs to be set."; exit 1; fi
+if [ -z ${FULL_BUILD+x} ] ; then echo "Variable 'FULL_BUILD' needs to be set."; exit 1; fi
+if [ -z ${MODEL+x} ] ; then echo "Variable 'MODEL' needs to be set."; exit 1; fi
+if [ -z ${DMD+x} ] ; then echo "Variable 'DMD' needs to be set."; exit 1; fi
+
+CURL_USER_AGENT="DMD-CI $(curl --version | head -n 1)"
+
+# use faster ld.gold linker on linux
+if [ "$OS_NAME" == "linux" ]; then
+    mkdir -p linker
+    rm -f linker/ld
+    ln -s /usr/bin/ld.gold linker/ld
+    NM="nm --print-size"
+    export PATH="$PWD/linker:$PATH"
+else
+    NM=nm
+fi
+
+# clone druntime and phobos
+clone() {
+    local url="$1"
+    local path="$2"
+    local branch="$3"
+    for i in {0..4}; do
+        if git clone --depth=1 --branch "$branch" "$url" "$path"; then
+            break
+        elif [ $i -lt 4 ]; then
+            sleep $((1 << $i))
+        else
+            echo "Failed to clone: ${url}"
+            exit 1
+        fi
+    done
+}
+
+# build dmd, druntime, phobos
+build() {
+    source ~/dlang/*/activate # activate host compiler
+    make -j$N -C src -f posix.mak MODEL=$MODEL HOST_DMD=$DMD ENABLE_RELEASE=1 ENABLE_WARNINGS=1 all
+    make -j$N -C ../druntime -f posix.mak MODEL=$MODEL
+    make -j$N -C ../phobos -f posix.mak MODEL=$MODEL
+    deactivate # deactivate host compiler
+}
+
+# self-compile dmd
+rebuild() {
+    local build_path=generated/$OS_NAME/release/$MODEL
+    local compare=${1:-0}
+    # `generated` gets cleaned in the next step, so we create another _generated
+    # The nested folder hierarchy is needed to conform to those specified in
+    # the generated dmd.conf
+    mkdir -p _${build_path}
+    cp $build_path/dmd _${build_path}/host_dmd
+    cp $build_path/dmd.conf _${build_path}
+    make -j$N -C src -f posix.mak MODEL=$MODEL HOST_DMD=../_${build_path}/host_dmd clean
+    make -j$N -C src -f posix.mak MODEL=$MODEL HOST_DMD=../_${build_path}/host_dmd ENABLE_RELEASE=1 ENABLE_WARNINGS=1 all
+
+    # compare binaries to test reproducible build
+    if [ $compare -eq 1 ]; then
+        if ! diff _${build_path}/host_dmd $build_path/dmd; then
+            $NM _${build_path}/host_dmd > a
+            $NM $build_path/dmd > b
+            diff -u a b
+            exit 1
+        fi
+    fi
+}
+
+# test druntime, phobos, dmd
+test() {
+    test_dub_package
+    make -j$N -C ../druntime -f posix.mak MODEL=$MODEL unittest
+    make -j$N -C ../phobos -f posix.mak MODEL=$MODEL unittest
+    test_dmd
+}
+
+# test dmd
+test_dmd() {
+    # test fewer compiler argument permutations for PRs to reduce CI load
+    if [ "$FULL_BUILD" == "true" ] && [ "$OS_NAME" == "linux"  ]; then
+        make -j$N -C test MODEL=$MODEL # all ARGS by default
+    else
+        make -j$N -C test MODEL=$MODEL ARGS="-O -inline -release"
+    fi
+}
+
+# test dub package
+test_dub_package() {
+    source ~/dlang/*/activate # activate host compiler
+    # GDC's standard library is too old for some example scripts
+    if [ "${DMD:-dmd}" == "gdmd" ] ; then
+        echo "Skipping DUB examples on GDC."
+    else
+        pushd test/dub_package
+        for file in *.d ; do
+            dub --single "$file"
+        done
+        popd
+    fi
+    deactivate
+}
+
+setup_repos() {
+for proj in druntime phobos; do
+    if [ $BRANCH != master ] && [ $BRANCH != stable ] &&
+           ! git ls-remote --exit-code --heads https://github.com/dlang/$proj.git $BRANCH > /dev/null; then
+        # use master as fallback for other repos to test feature branches
+        clone https://github.com/dlang/$proj.git ../$proj master
+    else
+        clone https://github.com/dlang/$proj.git ../$proj $BRANCH
+    fi
+done
+}
+
+testsuite() {
+    date
+    for step in build test rebuild "rebuild 1" test_dmd; do
+        $step
+        date
+    done
+}
+
+download_install_sh() {
+  local mirrors location
+  location="${1:-install.sh}"
+  mirrors=(
+    "https://dlang.org/install.sh"
+    "https://downloads.dlang.org/other/install.sh"
+    "https://nightlies.dlang.org/install.sh"
+    "https://github.com/dlang/installer/raw/master/script/install.sh"
+  )
+  if [ -f "$location" ] ; then
+      return
+  fi
+  for i in {0..4}; do
+    for mirror in "${mirrors[@]}" ; do
+        if curl -fsS -A "$CURL_USER_AGENT" --connect-timeout 5 --speed-time 30 --speed-limit 1024 "$mirror" -O ; then
+            break 2
+        fi
+    done
+    sleep $((1 << i))
+  done
+}
+
+activate_d() {
+  download_install_sh "$@"
+  CURL_USER_AGENT="$CURL_USER_AGENT" bash install.sh "$1" --activate
+}
diff --git a/semaphoreci.sh b/semaphoreci.sh
new file mode 100755
index 000000000000..a4055a68dd88
--- /dev/null
+++ b/semaphoreci.sh
@@ -0,0 +1,37 @@
+#!/bin/bash
+
+set -uexo pipefail
+
+################################################################################
+# Set by the Semaphore job runner
+################################################################################
+
+export MODEL=${MODEL:-64}      # can be {32,64}
+export DMD=${DMD:-dmd}         # can be {dmd,ldc,gdc}
+
+################################################################################
+# Static variables or inferred from Semaphore
+# See also: https://semaphoreci.com/docs/available-environment-variables.html
+################################################################################
+
+export N=4
+export OS_NAME=linux
+export BRANCH=$BRANCH_NAME
+export FULL_BUILD="${PULL_REQUEST_NUMBER+false}"
+
+source ci.sh
+
+################################################################################
+# Always source a DMD instance
+################################################################################
+
+source "$(activate_d "$DMD")"
+
+################################################################################
+# Define commands
+################################################################################
+
+case $1 in
+    setup) setup_repos ;;
+    testsuite) testsuite ;;
+esac
diff --git a/travis.sh b/travis.sh
index f25f115cd905..760b6133be0a 100755
--- a/travis.sh
+++ b/travis.sh
@@ -2,114 +2,22 @@
 
 set -uexo pipefail
 
-N=2
+################################################################################
+# Static variables or inferred from Travis
+# https://docs.travis-ci.com/user/environment-variables/
+################################################################################
 
-# use faster ld.gold linker on linux
-if [ "$TRAVIS_OS_NAME" == "linux" ]; then
-    mkdir linker
-    ln -s /usr/bin/ld.gold linker/ld
-    NM="nm --print-size"
-    export PATH="$PWD/linker:$PATH"
-else
-    NM=nm
-fi
+export N=2
+export OS_NAME="${TRAVIS_OS_NAME}"
+export MODEL="${MODEL}"
+export BRANCH="${TRAVIS_BRANCH}"
+export FULL_BUILD=false
 
-# clone druntime and phobos
-clone() {
-    local url="$1"
-    local path="$2"
-    local branch="$3"
-    for i in {0..4}; do
-        if git clone --depth=1 --branch "$branch" "$url" "$path"; then
-            break
-        elif [ $i -lt 4 ]; then
-            sleep $((1 << $i))
-        else
-            echo "Failed to clone: ${url}"
-            exit 1
-        fi
-    done
-}
+source ci.sh
 
-# build dmd, druntime, phobos
-build() {
-    source ~/dlang/*/activate # activate host compiler
-    make -j$N -C src -f posix.mak MODEL=$MODEL HOST_DMD=$DMD ENABLE_RELEASE=1 ENABLE_WARNINGS=1 all
-    make -j$N -C ../druntime -f posix.mak MODEL=$MODEL
-    make -j$N -C ../phobos -f posix.mak MODEL=$MODEL
-    deactivate # deactivate host compiler
-}
+################################################################################
+# Commands
+################################################################################
 
-# self-compile dmd
-rebuild() {
-    local build_path=generated/$TRAVIS_OS_NAME/release/$MODEL
-    local compare=${1:-0}
-    # `generated` gets cleaned in the next step, so we create another _generated
-    # The nested folder hierarchy is needed to conform to those specified in
-    # the generated dmd.conf
-    mkdir -p _${build_path}
-    cp $build_path/dmd _${build_path}/host_dmd
-    cp $build_path/dmd.conf _${build_path}
-    make -j$N -C src -f posix.mak MODEL=$MODEL HOST_DMD=../_${build_path}/host_dmd clean
-    make -j$N -C src -f posix.mak MODEL=$MODEL HOST_DMD=../_${build_path}/host_dmd ENABLE_RELEASE=1 ENABLE_WARNINGS=1 all
-
-    # compare binaries to test reproducibile build
-    if [ $compare -eq 1 ]; then
-        if ! diff _${build_path}/host_dmd $build_path/dmd; then
-            $NM _${build_path}/host_dmd > a
-            $NM $build_path/dmd > b
-            diff -u a b
-            exit 1
-        fi
-    fi
-}
-
-# test druntime, phobos, dmd
-test() {
-    test_dub_package
-    make -j$N -C ../druntime -f posix.mak MODEL=$MODEL unittest
-    make -j$N -C ../phobos -f posix.mak MODEL=$MODEL unittest
-    test_dmd
-}
-
-# test dmd
-test_dmd() {
-    # test fewer compiler argument permutations for PRs to reduce CI load
-    if [ "$TRAVIS_PULL_REQUEST" == "false" ] && [ "$TRAVIS_OS_NAME" == "linux"  ]; then
-        make -j$N -C test MODEL=$MODEL # all ARGS by default
-    else
-        make -j$N -C test MODEL=$MODEL ARGS="-O -inline -release"
-    fi
-}
-
-# test dub package
-test_dub_package() {
-    source ~/dlang/*/activate # activate host compiler
-    # GDC's standard library is too old for some example scripts
-    if [ "${DMD:-dmd}" == "gdmd" ] ; then
-        echo "Skipping DUB examples on GDC."
-    else
-        pushd test/dub_package
-        for file in *.d ; do
-            dub --single "$file"
-        done
-        popd
-    fi
-    deactivate
-}
-
-for proj in druntime phobos; do
-    if [ $TRAVIS_BRANCH != master ] && [ $TRAVIS_BRANCH != stable ] &&
-           ! git ls-remote --exit-code --heads https://github.com/dlang/$proj.git $TRAVIS_BRANCH > /dev/null; then
-        # use master as fallback for other repos to test feature branches
-        clone https://github.com/dlang/$proj.git ../$proj master
-    else
-        clone https://github.com/dlang/$proj.git ../$proj $TRAVIS_BRANCH
-    fi
-done
-
-date
-for step in build test rebuild "rebuild 1" test_dmd; do
-    $step
-    date
-done
+setup_repos
+testsuite