diff --git a/.circleci/config.yml b/.circleci/config.yml
index 8123fefe8..f592a8703 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1054,8 +1054,9 @@ jobs:
     docker:
       - image: circleci/node:<<parameters.nodejs_version>>
     resource_class: <<parameters.resource_class>>
-    # NOTE: Each external test does 3 separate compile&test runs
-    parallelism: 3
+    # NOTE: Each external test runs up to 6 independent settings presets. If parallelism is higher than
+    # actual preset count, some runs will exit immediately. If it's lower, some runs will get more than one preset.
+    parallelism: 6
     environment:
       TERM: xterm
       COMPILE_ONLY: <<parameters.compile_only>>
diff --git a/scripts/common.sh b/scripts/common.sh
index 3e67c4f56..4a98c0072 100644
--- a/scripts/common.sh
+++ b/scripts/common.sh
@@ -211,6 +211,7 @@ function safe_kill
 
 function circleci_select_steps
 {
+    # We expect multiple lines in $all_steps, one step per line
     local all_steps="$1"
     (( $# == 1 )) || assertFail
 
@@ -222,11 +223,26 @@ function circleci_select_steps
     fi
 }
 
+function circleci_select_steps_multiarg
+{
+    # We expect multiple arguments, one step per argument.
+    circleci_select_steps "$(printf '%s\n' "$@")"
+}
+
 function circleci_step_selected
 {
     local selected_steps="$1"
     local step="$2"
+    (( $# == 2 )) || assertFail
     [[ $step != *" "* ]] || assertFail "Step names must not contain spaces."
 
     [[ " $selected_steps " == *" $step "* ]] || return 1
 }
+
+function first_word
+{
+    local words="$1"
+    (( $# == 1 )) || assertFail
+
+    echo "$words" | cut -d " " -f 1
+}
diff --git a/test/externalTests/colony.sh b/test/externalTests/colony.sh
index 65a2183bc..d5b57f024 100755
--- a/test/externalTests/colony.sh
+++ b/test/externalTests/colony.sh
@@ -36,20 +36,25 @@ function colony_test
     local repo="https://github.com/solidity-external-tests/colonyNetwork.git"
     local branch=develop_080
     local config_file="truffle.js"
-    # On levels 1 and 2 it compiles but tests run out of gas
-    local min_optimizer_level=3
-    local max_optimizer_level=3
+    local settings_presets=(
+        #ir-no-optimize            # Compiles but tests run out of gas
+        #ir-optimize-evm-only      # Compiles but tests run out of gas
+        ir-optimize-evm+yul
+        #legacy-no-optimize        # Compiles but tests run out of gas
+        #legacy-optimize-evm-only  # Compiles but tests run out of gas
+        legacy-optimize-evm+yul
+    )
 
-    local selected_optimizer_levels
-    selected_optimizer_levels=$(circleci_select_steps "$(seq "$min_optimizer_level" "$max_optimizer_level")")
-    print_optimizer_levels_or_exit "$selected_optimizer_levels"
+    local selected_optimizer_presets
+    selected_optimizer_presets=$(circleci_select_steps_multiarg "${settings_presets[@]}")
+    print_optimizer_presets_or_exit "$selected_optimizer_presets"
 
     setup_solc "$DIR" "$BINARY_TYPE" "$BINARY_PATH"
     download_project "$repo" "$branch" "$DIR"
     [[ $BINARY_TYPE == native ]] && replace_global_solc "$BINARY_PATH"
 
     neutralize_package_json_hooks
-    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$min_optimizer_level"
+    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$(first_word "$selected_optimizer_presets")"
     yarn install
     git submodule update --init
 
@@ -61,8 +66,8 @@ function colony_test
     replace_version_pragmas
     [[ $BINARY_TYPE == solcjs ]] && force_solc_modules "${DIR}/solc"
 
-    for level in $selected_optimizer_levels; do
-        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$level" compile_fn test_fn
+    for preset in $selected_optimizer_presets; do
+        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$preset" compile_fn test_fn
     done
 }
 
diff --git a/test/externalTests/common.sh b/test/externalTests/common.sh
index 80a9dec32..012a21b2f 100644
--- a/test/externalTests/common.sh
+++ b/test/externalTests/common.sh
@@ -24,13 +24,13 @@ set -e
 
 CURRENT_EVM_VERSION=london
 
-function print_optimizer_levels_or_exit
+function print_optimizer_presets_or_exit
 {
-    local selected_levels="$1"
+    local selected_presets="$1"
 
-    [[ $selected_levels != "" ]] || { printWarning "No steps to run. Exiting."; exit 0; }
+    [[ $selected_presets != "" ]] || { printWarning "No presets to run. Exiting."; exit 0; }
 
-    printLog "Selected optimizer levels: ${selected_levels}"
+    printLog "Selected settings presets: ${selected_presets}"
 }
 
 function verify_input
@@ -141,7 +141,7 @@ function force_truffle_compiler_settings
     local config_file="$1"
     local binary_type="$2"
     local solc_path="$3"
-    local level="$4"
+    local preset="$4"
     local evm_version="${5:-"$CURRENT_EVM_VERSION"}"
 
     [[ $binary_type == native || $binary_type == solcjs ]] || assertFail
@@ -153,14 +153,16 @@ function force_truffle_compiler_settings
     echo "Config file: $config_file"
     echo "Binary type: $binary_type"
     echo "Compiler path: $solc_path"
-    echo "Optimization level: $level"
-    echo "Optimizer settings: $(optimizer_settings_for_level "$level")"
+    echo "Settings preset: ${preset}"
+    echo "Settings: $(settings_from_preset "$preset" "$evm_version")"
     echo "EVM version: $evm_version"
+    echo "Compiler version: ${SOLCVERSION_SHORT}"
+    echo "Compiler version (full): ${SOLCVERSION}"
     echo "-------------------------------------"
 
     # Forcing the settings should always work by just overwriting the solc object. Forcing them by using a
     # dedicated settings objects should only be the fallback.
-    echo "module.exports['compilers'] = $(truffle_compiler_settings "$solc_path" "$level" "$evm_version");" >> "$config_file"
+    echo "module.exports['compilers'] = $(truffle_compiler_settings "$solc_path" "$preset" "$evm_version");" >> "$config_file"
 }
 
 function force_hardhat_compiler_binary
@@ -180,14 +182,14 @@ function force_hardhat_compiler_binary
 function force_hardhat_compiler_settings
 {
     local config_file="$1"
-    local level="$2"
+    local preset="$2"
     local evm_version="${3:-"$CURRENT_EVM_VERSION"}"
 
     printLog "Configuring Hardhat..."
     echo "-------------------------------------"
     echo "Config file: ${config_file}"
-    echo "Optimization level: ${level}"
-    echo "Optimizer settings: $(optimizer_settings_for_level "$level")"
+    echo "Settings preset: ${preset}"
+    echo "Settings: $(settings_from_preset "$preset" "$evm_version")"
     echo "EVM version: ${evm_version}"
     echo "Compiler version: ${SOLCVERSION_SHORT}"
     echo "Compiler version (full): ${SOLCVERSION}"
@@ -195,7 +197,7 @@ function force_hardhat_compiler_settings
 
     {
         echo -n 'module.exports["solidity"] = '
-        hardhat_compiler_settings "$SOLCVERSION_SHORT" "$level" "$evm_version"
+        hardhat_compiler_settings "$SOLCVERSION_SHORT" "$preset" "$evm_version"
     } >> "$config_file"
 }
 
@@ -236,22 +238,27 @@ function run_test
     replace_version_pragmas
 
     printLog "Running compile function..."
-    $compile_fn
+    time $compile_fn
 
     printLog "Running test function..."
     $test_fn
 }
 
-function optimizer_settings_for_level
+function settings_from_preset
 {
-    local level="$1"
+    local preset="$1"
+    local evm_version="$2"
 
-    case "$level" in
-        1) echo "{enabled: false}" ;;
-        2) echo "{enabled: true, details: {yul: false}}" ;;
-        3) echo "{enabled: true, details: {yul: true}}" ;;
+    case "$preset" in
+        # NOTE: Remember to update `parallelism` of `t_ems_ext` job in CI config if you add/remove presets
+        legacy-no-optimize)       echo "{evmVersion: '${evm_version}', viaIR: false, optimizer: {enabled: false}}" ;;
+        ir-no-optimize)           echo "{evmVersion: '${evm_version}', viaIR: true,  optimizer: {enabled: false}}" ;;
+        legacy-optimize-evm-only) echo "{evmVersion: '${evm_version}', viaIR: false, optimizer: {enabled: true, details: {yul: false}}}" ;;
+        ir-optimize-evm-only)     echo "{evmVersion: '${evm_version}', viaIR: true,  optimizer: {enabled: true, details: {yul: false}}}" ;;
+        legacy-optimize-evm+yul)  echo "{evmVersion: '${evm_version}', viaIR: false, optimizer: {enabled: true, details: {yul: true}}}" ;;
+        ir-optimize-evm+yul)      echo "{evmVersion: '${evm_version}', viaIR: true,  optimizer: {enabled: true, details: {yul: true}}}" ;;
         *)
-            fail "Optimizer level not found. Please define OPTIMIZER_LEVEL=[1, 2, 3]"
+            fail "Unknown settings preset: '${preset}'."
             ;;
     esac
 }
@@ -269,16 +276,13 @@ function replace_global_solc
 function truffle_compiler_settings
 {
     local solc_path="$1"
-    local level="$2"
+    local preset="$2"
     local evm_version="$3"
 
     echo "{"
     echo "    solc: {"
     echo "        version: \"${solc_path}\","
-    echo "        settings: {"
-    echo "            optimizer: $(optimizer_settings_for_level "$level"),"
-    echo "            evmVersion: \"${evm_version}\""
-    echo "        }"
+    echo "        settings: $(settings_from_preset "$preset" "$evm_version")"
     echo "    }"
     echo "}"
 }
@@ -310,15 +314,12 @@ function hardhat_solc_build_subtask {
 
 function hardhat_compiler_settings {
     local solc_version="$1"
-    local level="$2"
+    local preset="$2"
     local evm_version="$3"
 
     echo "{"
     echo "    version: '${solc_version}',"
-    echo "    settings: {"
-    echo "        optimizer: $(optimizer_settings_for_level "$level"),"
-    echo "        evmVersion: '${evm_version}'"
-    echo "    }"
+    echo "    settings: $(settings_from_preset "$preset" "$evm_version")"
     echo "}"
 }
 
@@ -329,7 +330,7 @@ function compile_and_run_test
     local verify_fn="$3"
 
     printLog "Running compile function..."
-    $compile_fn
+    time $compile_fn
     $verify_fn "$SOLCVERSION_SHORT" "$SOLCVERSION"
 
     if [[ "$COMPILE_ONLY" == 1 ]]; then
@@ -345,24 +346,24 @@ function truffle_run_test
     local config_file="$1"
     local binary_type="$2"
     local solc_path="$3"
-    local optimizer_level="$4"
+    local preset="$4"
     local compile_fn="$5"
     local test_fn="$6"
 
     truffle_clean
-    force_truffle_compiler_settings "$config_file" "$binary_type" "$solc_path" "$optimizer_level"
+    force_truffle_compiler_settings "$config_file" "$binary_type" "$solc_path" "$preset"
     compile_and_run_test compile_fn test_fn truffle_verify_compiler_version
 }
 
 function hardhat_run_test
 {
     local config_file="$1"
-    local optimizer_level="$2"
+    local preset="$2"
     local compile_fn="$3"
     local test_fn="$4"
 
     hardhat_clean
-    force_hardhat_compiler_settings "$config_file" "$optimizer_level"
+    force_hardhat_compiler_settings "$config_file" "$preset"
     compile_and_run_test compile_fn test_fn hardhat_verify_compiler_version
 }
 
diff --git a/test/externalTests/ens.sh b/test/externalTests/ens.sh
index 7b354acde..c0bc4b558 100755
--- a/test/externalTests/ens.sh
+++ b/test/externalTests/ens.sh
@@ -36,12 +36,18 @@ function ens_test
     local repo="https://github.com/ensdomains/ens.git"
     local branch=master
     local config_file="truffle.js"
-    local min_optimizer_level=1
-    local max_optimizer_level=3
+    local settings_presets=(
+        #ir-no-optimize           # "YulException: Variable var_ttl_236 is 1 slot(s) too deep inside the stack."
+        #ir-optimize-evm-only     # "YulException: Variable var_ttl_236 is 1 slot(s) too deep inside the stack."
+        ir-optimize-evm+yul
+        legacy-no-optimize
+        legacy-optimize-evm-only
+        legacy-optimize-evm+yul
+    )
 
-    local selected_optimizer_levels
-    selected_optimizer_levels=$(circleci_select_steps "$(seq "$min_optimizer_level" "$max_optimizer_level")")
-    print_optimizer_levels_or_exit "$selected_optimizer_levels"
+    local selected_optimizer_presets
+    selected_optimizer_presets=$(circleci_select_steps_multiarg "${settings_presets[@]}")
+    print_optimizer_presets_or_exit "$selected_optimizer_presets"
 
     setup_solc "$DIR" "$BINARY_TYPE" "$BINARY_PATH"
     download_project "$repo" "$branch" "$DIR"
@@ -52,14 +58,14 @@ function ens_test
 
     neutralize_package_lock
     neutralize_package_json_hooks
-    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$min_optimizer_level"
+    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$(first_word "$selected_optimizer_presets")"
     npm install
 
     replace_version_pragmas
     [[ $BINARY_TYPE == solcjs ]] && force_solc_modules "${DIR}/solc"
 
-    for level in $selected_optimizer_levels; do
-        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$level" compile_fn test_fn
+    for preset in $selected_optimizer_presets; do
+        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$preset" compile_fn test_fn
     done
 }
 
diff --git a/test/externalTests/gnosis-v2.sh b/test/externalTests/gnosis-v2.sh
index b71749a06..bae0f0f1e 100755
--- a/test/externalTests/gnosis-v2.sh
+++ b/test/externalTests/gnosis-v2.sh
@@ -36,13 +36,18 @@ function gnosis_safe_test
     local repo="https://github.com/solidity-external-tests/safe-contracts.git"
     local branch=v2_080
     local config_file="truffle-config.js"
-    # level 1: "Error: while migrating GnosisSafe: Returned error: base fee exceeds gas limit"
-    local min_optimizer_level=2
-    local max_optimizer_level=3
+    local settings_presets=(
+        #ir-no-optimize           # "YulException: Variable var_call_430_mpos is 1 slot(s) too deep inside the stack."
+        #ir-optimize-evm-only     # "YulException: Variable var_call_430_mpos is 1 slot(s) too deep inside the stack."
+        ir-optimize-evm+yul
+        #legacy-no-optimize       # "Error: while migrating GnosisSafe: Returned error: base fee exceeds gas limit"
+        legacy-optimize-evm-only
+        legacy-optimize-evm+yul
+    )
 
-    local selected_optimizer_levels
-    selected_optimizer_levels=$(circleci_select_steps "$(seq "$min_optimizer_level" "$max_optimizer_level")")
-    print_optimizer_levels_or_exit "$selected_optimizer_levels"
+    local selected_optimizer_presets
+    selected_optimizer_presets=$(circleci_select_steps_multiarg "${settings_presets[@]}")
+    print_optimizer_presets_or_exit "$selected_optimizer_presets"
 
     setup_solc "$DIR" "$BINARY_TYPE" "$BINARY_PATH"
     download_project "$repo" "$branch" "$DIR"
@@ -53,14 +58,14 @@ function gnosis_safe_test
 
     neutralize_package_lock
     neutralize_package_json_hooks
-    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$min_optimizer_level"
+    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$(first_word "$selected_optimizer_presets")"
     npm install --package-lock
 
     replace_version_pragmas
     [[ $BINARY_TYPE == solcjs ]] && force_solc_modules "${DIR}/solc"
 
-    for level in $selected_optimizer_levels; do
-        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$level" compile_fn test_fn
+    for preset in $selected_optimizer_presets; do
+        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$preset" compile_fn test_fn
     done
 }
 
diff --git a/test/externalTests/gnosis.sh b/test/externalTests/gnosis.sh
index 97208660b..562ab156f 100755
--- a/test/externalTests/gnosis.sh
+++ b/test/externalTests/gnosis.sh
@@ -36,13 +36,18 @@ function gnosis_safe_test
     local repo="https://github.com/solidity-external-tests/safe-contracts.git"
     local branch=development_080
     local config_file="truffle-config.js"
-    # levels 1 and 2: "Stack too deep" error
-    local min_optimizer_level=3
-    local max_optimizer_level=3
+    local settings_presets=(
+        #ir-no-optimize            # "YulException: Variable var_call_430_mpos is 1 slot(s) too deep inside the stack."
+        #ir-optimize-evm-only      # "YulException: Variable var_call_430_mpos is 1 slot(s) too deep inside the stack."
+        ir-optimize-evm+yul
+        #legacy-no-optimize        # "Stack too deep" error
+        #legacy-optimize-evm-only  # "Stack too deep" error
+        legacy-optimize-evm+yul
+    )
 
-    local selected_optimizer_levels
-    selected_optimizer_levels=$(circleci_select_steps "$(seq "$min_optimizer_level" "$max_optimizer_level")")
-    print_optimizer_levels_or_exit "$selected_optimizer_levels"
+    local selected_optimizer_presets
+    selected_optimizer_presets=$(circleci_select_steps_multiarg "${settings_presets[@]}")
+    print_optimizer_presets_or_exit "$selected_optimizer_presets"
 
     setup_solc "$DIR" "$BINARY_TYPE" "$BINARY_PATH"
     download_project "$repo" "$branch" "$DIR"
@@ -52,14 +57,14 @@ function gnosis_safe_test
 
     neutralize_package_lock
     neutralize_package_json_hooks
-    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$min_optimizer_level"
+    force_truffle_compiler_settings "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$(first_word "$selected_optimizer_presets")"
     npm install --package-lock
 
     replace_version_pragmas
     [[ $BINARY_TYPE == solcjs ]] && force_solc_modules "${DIR}/solc"
 
-    for level in $selected_optimizer_levels; do
-        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$level" compile_fn test_fn
+    for preset in $selected_optimizer_presets; do
+        truffle_run_test "$config_file" "$BINARY_TYPE" "${DIR}/solc" "$preset" compile_fn test_fn
     done
 }
 
diff --git a/test/externalTests/zeppelin.sh b/test/externalTests/zeppelin.sh
index 0759a3aec..89f3d6b42 100755
--- a/test/externalTests/zeppelin.sh
+++ b/test/externalTests/zeppelin.sh
@@ -36,25 +36,31 @@ function zeppelin_test
     local repo="https://github.com/OpenZeppelin/openzeppelin-contracts.git"
     local branch=master
     local config_file="hardhat.config.js"
-    local min_optimizer_level=1
-    local max_optimizer_level=3
+    local settings_presets=(
+        #ir-no-optimize           # "YulException: Variable var_account_852 is 4 slot(s) too deep inside the stack."
+        #ir-optimize-evm-only     # "YulException: Variable var_account_852 is 4 slot(s) too deep inside the stack."
+        #ir-optimize-evm+yul      # Compiles but tests fail. See https://github.com/nomiclabs/hardhat/issues/2115
+        legacy-no-optimize
+        legacy-optimize-evm-only
+        legacy-optimize-evm+yul
+    )
 
-    local selected_optimizer_levels
-    selected_optimizer_levels=$(circleci_select_steps "$(seq "$min_optimizer_level" "$max_optimizer_level")")
-    print_optimizer_levels_or_exit "$selected_optimizer_levels"
+    local selected_optimizer_presets
+    selected_optimizer_presets=$(circleci_select_steps_multiarg "${settings_presets[@]}")
+    print_optimizer_presets_or_exit "$selected_optimizer_presets"
 
     setup_solc "$DIR" "$BINARY_TYPE" "$BINARY_PATH"
     download_project "$repo" "$branch" "$DIR"
 
     neutralize_package_json_hooks
     force_hardhat_compiler_binary "$config_file" "$BINARY_TYPE" "$BINARY_PATH"
-    force_hardhat_compiler_settings "$config_file" "$min_optimizer_level"
+    force_hardhat_compiler_settings "$config_file" "$(first_word "$selected_optimizer_presets")"
     npm install
 
     replace_version_pragmas
 
-    for level in $selected_optimizer_levels; do
-        hardhat_run_test "$config_file" "$level" compile_fn test_fn
+    for preset in $selected_optimizer_presets; do
+        hardhat_run_test "$config_file" "$preset" compile_fn test_fn
     done
 }