Merge pull request #8878 from ethereum/selecting-yul-optimisation-steps-in-strict-assembly-mode

Selecting Yul optimisation steps in strict assembly mode

Changelog.md

@@ -5,6 +5,7 @@ Language Features:
 
 
 Compiler Features:
+ * Commandline Interface: Don't ignore `--yul-optimizations` in assembly mode.
 
 
 

docs/yul.rst

@@ -1041,14 +1041,16 @@ Optimization step sequence
 --------------------------
 
 By default the Yul optimizer applies its predefined sequence of optimization steps to the generated assembly.
-You can override this sequence and supply your own using the `--yul-optimizations` option when compiling
-in Solidity mode:
+You can override this sequence and supply your own using the ``--yul-optimizations`` option:
 
 .. code-block:: sh
 
     solc --optimize --ir-optimized --yul-optimizations 'dhfoD[xarrscLMcCTU]uljmul'
 
-By enclosing part of the sequence in square brackets (`[]`) you tell the optimizer to repeatedly
+The order of steps is significant and affects the quality of the output.
+Moreover, applying a step may uncover new optimization opportunities for others that were already
+applied so repeating steps is often beneficial.
+By enclosing part of the sequence in square brackets (``[]``) you tell the optimizer to repeatedly
 apply that part until it no longer improves the size of the resulting assembly.
 You can use brackets multiple times in a single sequence but they cannot be nested.
 
@@ -1057,37 +1059,37 @@ The following optimization steps are available:
 ============ ===============================
 Abbreviation Full name
 ============ ===============================
-f            `BlockFlattener`
-l            `CircularReferencesPruner`
-c            `CommonSubexpressionEliminator`
-C            `ConditionalSimplifier`
-U            `ConditionalUnsimplifier`
-n            `ControlFlowSimplifier`
-D            `DeadCodeEliminator`
-v            `EquivalentFunctionCombiner`
-e            `ExpressionInliner`
-j            `ExpressionJoiner`
-s            `ExpressionSimplifier`
-x            `ExpressionSplitter`
-I            `ForLoopConditionIntoBody`
-O            `ForLoopConditionOutOfBody`
-o            `ForLoopInitRewriter`
-i            `FullInliner`
-g            `FunctionGrouper`
-h            `FunctionHoister`
-T            `LiteralRematerialiser`
-L            `LoadResolver`
-M            `LoopInvariantCodeMotion`
-r            `RedundantAssignEliminator`
-m            `Rematerialiser`
-V            `SSAReverser`
-a            `SSATransform`
-t            `StructuralSimplifier`
-u            `UnusedPruner`
-d            `VarDeclInitializer`
+``f``        ``BlockFlattener``
+``l``        ``CircularReferencesPruner``
+``c``        ``CommonSubexpressionEliminator``
+``C``        ``ConditionalSimplifier``
+``U``        ``ConditionalUnsimplifier``
+``n``        ``ControlFlowSimplifier``
+``D``        ``DeadCodeEliminator``
+``v``        ``EquivalentFunctionCombiner``
+``e``        ``ExpressionInliner``
+``j``        ``ExpressionJoiner``
+``s``        ``ExpressionSimplifier``
+``x``        ``ExpressionSplitter``
+``I``        ``ForLoopConditionIntoBody``
+``O``        ``ForLoopConditionOutOfBody``
+``o``        ``ForLoopInitRewriter``
+``i``        ``FullInliner``
+``g``        ``FunctionGrouper``
+``h``        ``FunctionHoister``
+``T``        ``LiteralRematerialiser``
+``L``        ``LoadResolver``
+``M``        ``LoopInvariantCodeMotion``
+``r``        ``RedundantAssignEliminator``
+``m``        ``Rematerialiser``
+``V``        ``SSAReverser``
+``a``        ``SSATransform``
+``t``        ``StructuralSimplifier``
+``u``        ``UnusedPruner``
+``d``        ``VarDeclInitializer``
 ============ ===============================
 
-Some steps depend on properties ensured by `BlockFlattener`, `FunctionGrouper`, `ForLoopInitRewriter`.
+Some steps depend on properties ensured by ``BlockFlattener``, ``FunctionGrouper``, ``ForLoopInitRewriter``.
 For this reason the Yul optimizer always applies them before applying any steps supplied by the user.
 
 

libyul/optimiser/README.md

@@ -4,6 +4,7 @@ planned state of the optimiser.
 
 Table of Contents:
 
+- [Selecting optimisations](#selecting-optimisations)
 - [Preprocessing](#preprocessing)
 - [Pseudo-SSA Transformation](#pseudo-ssa-transformation)
 - [Tools](#tools)
@@ -33,6 +34,17 @@ the following transformation steps are the main components:
  - [Redundant Assign Eliminator](#redundant-assign-eliminator)
  - [Full Function Inliner](#full-function-inliner)
 
+## Selecting optimisations
+
+By default the optimiser applies its predefined sequence of optimisation steps to the generated assembly.
+You can override this sequence and supply your own using the `--yul-optimizations` option:
+
+``` bash
+solc --optimize --ir-optimized --yul-optimizations 'dhfoD[xarrscLMcCTU]uljmul'
+```
+
+There's a [table listing available abbreviations in the optimiser docs](/docs/yul.rst#optimization-step-sequence).
+
 ## Preprocessing
 
 The preprocessing components perform transformations to get the program

solc/CommandLineInterface.cpp

@@ -699,7 +699,7 @@ void CommandLineInterface::createFile(string const& _fileName, string const& _da
 	string pathName = (p / _fileName).string();
 	if (fs::exists(pathName) && !m_args.count(g_strOverwrite))
 	{
-		serr() << "Refusing to overwrite existing file \"" << pathName << "\" (use --overwrite to force)." << endl;
+		serr() << "Refusing to overwrite existing file \"" << pathName << "\" (use --" << g_strOverwrite << " to force)." << endl;
 		m_error = true;
 		return;
 	}
@@ -719,10 +719,10 @@ bool CommandLineInterface::parseArguments(int _argc, char** _argv)
 	g_hasOutput = false;
 
 	// Declare the supported options.
-	po::options_description desc(R"(solc, the Solidity commandline compiler.
+	po::options_description desc((R"(solc, the Solidity commandline compiler.
 
 This program comes with ABSOLUTELY NO WARRANTY. This is free software, and you
-are welcome to redistribute it under certain conditions. See 'solc --license'
+are welcome to redistribute it under certain conditions. See 'solc --)" + g_strLicense + R"('
 for details.
 
 Usage: solc [options] [input_file...]
@@ -732,9 +732,9 @@ at standard output or in files in the output directory, if specified.
 Imports are automatically read from the filesystem, but it is also possible to
 remap paths using the context:prefix=path syntax.
 Example:
-solc --bin -o /tmp/solcoutput dapp-bin=/usr/local/lib/dapp-bin contract.sol
+solc --)" + g_argBinary + R"( -o /tmp/solcoutput dapp-bin=/usr/local/lib/dapp-bin contract.sol
 
-Allowed options)",
+Allowed options)").c_str(),
 		po::options_description::m_default_line_length,
 		po::options_description::m_default_line_length - 23
 	);
@@ -780,20 +780,27 @@ Allowed options)",
 		)
 		(
 			g_argImportAst.c_str(),
-			"Import ASTs to be compiled, assumes input holds the AST in compact JSON format. "
-			"Supported Inputs is the output of the --standard-json or the one produced by --combined-json ast,compact-format"
+			("Import ASTs to be compiled, assumes input holds the AST in compact JSON format. "
+			"Supported Inputs is the output of the --" + g_argStandardJSON + " or the one produced by "
+			"--" + g_argCombinedJson + " " + g_strAst + "," + g_strCompactJSON).c_str()
 		)
 		(
 			g_argAssemble.c_str(),
-			"Switch to assembly mode, ignoring all options except --machine, --yul-dialect and --optimize and assumes input is assembly."
+			("Switch to assembly mode, ignoring all options except "
+			"--" + g_argMachine + ", --" + g_strYulDialect + ", --" + g_argOptimize + " and --" + g_strYulOptimizations + " "
+			"and assumes input is assembly.").c_str()
 		)
 		(
 			g_argYul.c_str(),
-			"Switch to Yul mode, ignoring all options except --machine, --yul-dialect and --optimize and assumes input is Yul."
+			("Switch to Yul mode, ignoring all options except "
+			"--" + g_argMachine + ", --" + g_strYulDialect + ", --" + g_argOptimize + " and --" + g_strYulOptimizations + " "
+			"and assumes input is Yul.").c_str()
 		)
 		(
 			g_argStrictAssembly.c_str(),
-			"Switch to strict assembly mode, ignoring all options except --machine, --yul-dialect and --optimize and assumes input is strict assembly."
+			("Switch to strict assembly mode, ignoring all options except "
+			"--" + g_argMachine + ", --" + g_strYulDialect + ", --" + g_argOptimize + " and --" + g_strYulOptimizations + " "
+			"and assumes input is strict assembly.").c_str()
 		)
 		(
 			g_strYulDialect.c_str(),
@@ -807,8 +814,8 @@ Allowed options)",
 		)
 		(
 			g_argLink.c_str(),
-			"Switch to linker mode, ignoring all options apart from --libraries "
-			"and modify binaries in place."
+			("Switch to linker mode, ignoring all options apart from --" + g_argLibraries + " "
+			"and modify binaries in place.").c_str()
 		)
 		(
 			g_argMetadataHash.c_str(),
@@ -835,7 +842,7 @@ Allowed options)",
 			"Set for how many contract runs to optimize. "
 			"Lower values will optimize more for initial deployment cost, higher values will optimize more for high-frequency usage."
 		)
-		(g_strOptimizeYul.c_str(), "Legacy option, ignored. Use the general --optimize to enable Yul optimizer.")
+		(g_strOptimizeYul.c_str(), ("Legacy option, ignored. Use the general --" + g_argOptimize + " to enable Yul optimizer.").c_str())
 		(g_strNoOptimizeYul.c_str(), "Disable Yul optimizer in Solidity.")
 		(
 			g_strYulOptimizations.c_str(),
@@ -933,7 +940,7 @@ Allowed options)",
 		for (string const& item: boost::split(requests, m_args[g_argCombinedJson].as<string>(), boost::is_any_of(",")))
 			if (!g_combinedJsonArgs.count(item))
 			{
-				serr() << "Invalid option to --combined-json: " << item << endl;
+				serr() << "Invalid option to --" << g_argCombinedJson << ": " << item << endl;
 				return false;
 			}
 	}
@@ -1047,7 +1054,7 @@ bool CommandLineInterface::processInput()
 		std::optional<langutil::EVMVersion> versionOption = langutil::EVMVersion::fromString(versionOptionStr);
 		if (!versionOption)
 		{
-			serr() << "Invalid option for --evm-version: " << versionOptionStr << endl;
+			serr() << "Invalid option for --" << g_strEVMVersion << ": " << versionOptionStr << endl;
 			return false;
 		}
 		m_evmVersion = *versionOption;
@@ -1064,14 +1071,37 @@ bool CommandLineInterface::processInput()
 		bool optimize = m_args.count(g_argOptimize);
 		if (m_args.count(g_strOptimizeYul))
 		{
-			serr() << "--optimize-yul is invalid in assembly mode. Use --optimize instead." << endl;
+			serr() << "--" << g_strOptimizeYul << " is invalid in assembly mode. Use --" << g_argOptimize << " instead." << endl;
 			return false;
 		}
 		if (m_args.count(g_strNoOptimizeYul))
 		{
-			serr() << "--no-optimize-yul is invalid in assembly mode. Optimization is disabled by default and can be enabled with --optimize." << endl;
+			serr() << "--" << g_strNoOptimizeYul << " is invalid in assembly mode. Optimization is disabled by default and can be enabled with --" << g_argOptimize << "." << endl;
 			return false;
 		}
+
+		optional<string> yulOptimiserSteps;
+		if (m_args.count(g_strYulOptimizations))
+		{
+			if (!optimize)
+			{
+				serr() << "--" << g_strYulOptimizations << " is invalid if Yul optimizer is disabled" << endl;
+				return false;
+			}
+
+			try
+			{
+				yul::OptimiserSuite::validateSequence(m_args[g_strYulOptimizations].as<string>());
+			}
+			catch (yul::OptimizerException const& _exception)
+			{
+				serr() << "Invalid optimizer step sequence in --" << g_strYulOptimizations << ": " << _exception.what() << endl;
+				return false;
+			}
+
+			yulOptimiserSteps = m_args[g_strYulOptimizations].as<string>();
+		}
+
 		if (m_args.count(g_argMachine))
 		{
 			string machine = m_args[g_argMachine].as<string>();
@@ -1083,7 +1113,7 @@ bool CommandLineInterface::processInput()
 				targetMachine = Machine::Ewasm;
 			else
 			{
-				serr() << "Invalid option for --machine: " << machine << endl;
+				serr() << "Invalid option for --" << g_argMachine << ": " << machine << endl;
 				return false;
 			}
 		}
@@ -1099,13 +1129,14 @@ bool CommandLineInterface::processInput()
 				inputLanguage = Input::Ewasm;
 				if (targetMachine != Machine::Ewasm)
 				{
-					serr() << "If you select Ewasm as --yul-dialect, --machine has to be Ewasm as well." << endl;
+					serr() << "If you select Ewasm as --" << g_strYulDialect << ", ";
+					serr() << "--" << g_argMachine << " has to be Ewasm as well." << endl;
 					return false;
 				}
 			}
 			else
 			{
-				serr() << "Invalid option for --yul-dialect: " << dialect << endl;
+				serr() << "Invalid option for --" << g_strYulDialect << ": " << dialect << endl;
 				return false;
 			}
 		}
@@ -1122,7 +1153,7 @@ bool CommandLineInterface::processInput()
 			"Warning: Yul is still experimental. Please use the output with care." <<
 			endl;
 
-		return assemble(inputLanguage, targetMachine, optimize);
+		return assemble(inputLanguage, targetMachine, optimize, yulOptimiserSteps);
 	}
 	if (m_args.count(g_argLink))
 	{
@@ -1142,7 +1173,7 @@ bool CommandLineInterface::processInput()
 			m_metadataHash = CompilerStack::MetadataHash::None;
 		else
 		{
-			serr() << "Invalid option for --metadata-hash: " << hashStr << endl;
+			serr() << "Invalid option for --" << g_argMetadataHash << ": " << hashStr << endl;
 			return false;
 		}
 	}
@@ -1534,18 +1565,21 @@ string CommandLineInterface::objectWithLinkRefsHex(evmasm::LinkerObject const& _
 bool CommandLineInterface::assemble(
 	yul::AssemblyStack::Language _language,
 	yul::AssemblyStack::Machine _targetMachine,
-	bool _optimize
+	bool _optimize,
+	optional<string> _yulOptimiserSteps
 )
 {
+	solAssert(_optimize || !_yulOptimiserSteps.has_value(), "");
+
 	bool successful = true;
 	map<string, yul::AssemblyStack> assemblyStacks;
 	for (auto const& src: m_sourceCodes)
 	{
-		auto& stack = assemblyStacks[src.first] = yul::AssemblyStack(
-			m_evmVersion,
-			_language,
-			_optimize ? OptimiserSettings::full() : OptimiserSettings::minimal()
-		);
+		OptimiserSettings settings = _optimize ? OptimiserSettings::full() : OptimiserSettings::minimal();
+		if (_yulOptimiserSteps.has_value())
+			settings.yulOptimiserSteps = _yulOptimiserSteps.value();
+
+		auto& stack = assemblyStacks[src.first] = yul::AssemblyStack(m_evmVersion, _language, settings);
 		try
 		{
 			if (!stack.parseAndAnalyze(src.first, src.second))

solc/CommandLineInterface.h

@@ -56,7 +56,12 @@ private:
 	/// @returns the full object with library placeholder hints in hex.
 	static std::string objectWithLinkRefsHex(evmasm::LinkerObject const& _obj);
 
-	bool assemble(yul::AssemblyStack::Language _language, yul::AssemblyStack::Machine _targetMachine, bool _optimize);
+	bool assemble(
+		yul::AssemblyStack::Language _language,
+		yul::AssemblyStack::Machine _targetMachine,
+		bool _optimize,
+		std::optional<std::string> _yulOptimiserSteps = std::nullopt
+	);
 
 	void outputCompilationResults();
 

test/cmdlineTests.sh

@@ -245,7 +245,18 @@ printTask "Running general commandline tests..."
             stdoutExpectationFile="${tdir}/output.json"
             args="--standard-json "$(cat ${tdir}/args 2>/dev/null || true)
         else
-            inputFile="${tdir}input.sol"
+            if [[ -e "${tdir}input.yul" && -e "${tdir}input.sol" ]]
+            then
+                printError "Ambiguous input. Found both input.sol and input.yul."
+                exit 1
+            fi
+
+            if [ -e "${tdir}input.yul" ]
+            then
+                inputFile="${tdir}input.yul"
+            else
+                inputFile="${tdir}input.sol"
+            fi
             stdin=""
             stdout="$(cat ${tdir}/output 2>/dev/null || true)"
             stdoutExpectationFile="${tdir}/output"

test/cmdlineTests/standard_yul_optimiserSteps/input.json

@@ -0,0 +1,26 @@
+{
+	"language": "Yul",
+	"sources":
+	{
+		"A":
+		{
+			"content": "{ let x := mload(0) sstore(add(x, 0), 0) }"
+		}
+	},
+	"settings":
+	{
+		"optimizer": {
+			"enabled": true,
+			"details": {
+				"yul": true,
+				"yulDetails": {
+					"optimizerSteps": "dhfoDgvulfnTUtnIf"
+				}
+			}
+		},
+		"outputSelection":
+		{
+			"*": { "*": ["*"], "": [ "*" ] }
+		}
+	}
+}

test/cmdlineTests/standard_yul_optimiserSteps/output.json

@@ -0,0 +1,30 @@
+{"contracts":{"A":{"object":{"evm":{"assembly":"    /* \"A\":17:18   */
+  0x00
+    /* \"A\":11:19   */
+  mload
+    /* \"A\":38:39   */
+  0x00
+    /* \"A\":34:35   */
+  0x00
+    /* \"A\":31:32   */
+  dup3
+    /* \"A\":27:36   */
+  add
+    /* \"A\":20:40   */
+  sstore
+  pop
+","bytecode":{"linkReferences":{},"object":"bytecode removed","opcodes":"opcodes removed","sourceMap":"sourceMap removed"}},"ir":"object \"object\" {
+    code {
+        let x := mload(0)
+        sstore(add(x, 0), 0)
+    }
+}
+","irOptimized":"object \"object\" {
+    code {
+        {
+            let x := mload(0)
+            sstore(add(x, 0), 0)
+        }
+    }
+}
+"}}},"errors":[{"component":"general","formattedMessage":"Yul is still experimental. Please use the output with care.","message":"Yul is still experimental. Please use the output with care.","severity":"warning","type":"Warning"}]}

test/cmdlineTests/strict_asm_optimizer_steps/args

@@ -0,0 +1 @@
+--strict-assembly --optimize --yul-optimizations dhfoDgvulfnTUtnIf

test/cmdlineTests/strict_asm_optimizer_steps/err

@@ -0,0 +1 @@
+Warning: Yul is still experimental. Please use the output with care.

test/cmdlineTests/strict_asm_optimizer_steps/input.yul

@@ -0,0 +1,27 @@
+object "C_6" {
+    code {
+        mstore(64, 128)
+        if callvalue() { revert(0, 0) }
+        codecopy(0, dataoffset("C_6_deployed"), datasize("C_6_deployed"))
+        return(0, datasize("C_6_deployed"))
+    }
+    object "C_6_deployed" {
+        code {
+            {
+                mstore(64, 128)
+                if iszero(lt(calldatasize(), 4))
+                {
+                    let selector := shift_right_224_unsigned(calldataload(0))
+                    pop(selector)
+                }
+                pop(iszero(calldatasize()))
+                revert(0, 0)
+            }
+
+            function shift_right_224_unsigned(value) -> newValue
+            {
+                newValue := shr(224, value)
+            }
+        }
+    }
+}

test/cmdlineTests/strict_asm_optimizer_steps/output

@@ -0,0 +1,88 @@
+
+======= strict_asm_optimizer_steps/input.yul (EVM) =======
+
+Pretty printed source:
+object "C_6" {
+    code {
+        {
+            mstore(64, 128)
+            if callvalue() { revert(0, 0) }
+            codecopy(0, dataoffset("C_6_deployed"), datasize("C_6_deployed"))
+            return(0, datasize("C_6_deployed"))
+        }
+    }
+    object "C_6_deployed" {
+        code {
+            {
+                mstore(64, 128)
+                pop(iszero(lt(calldatasize(), 4)))
+                revert(0, 0)
+            }
+        }
+    }
+}
+
+
+Binary representation:
+60806040523415600f5760006000fd5b6010601d60003960106000f3fe608060405260043610155060006000fd
+
+Text representation:
+    /* "strict_asm_optimizer_steps/input.yul":45:48   */
+  0x80
+    /* "strict_asm_optimizer_steps/input.yul":41:43   */
+  0x40
+    /* "strict_asm_optimizer_steps/input.yul":34:49   */
+  mstore
+    /* "strict_asm_optimizer_steps/input.yul":61:72   */
+  callvalue
+    /* "strict_asm_optimizer_steps/input.yul":58:60   */
+  iszero
+  tag_1
+  jumpi
+    /* "strict_asm_optimizer_steps/input.yul":85:86   */
+  0x00
+    /* "strict_asm_optimizer_steps/input.yul":82:83   */
+  0x00
+    /* "strict_asm_optimizer_steps/input.yul":75:87   */
+  revert
+    /* "strict_asm_optimizer_steps/input.yul":58:60   */
+tag_1:
+    /* "strict_asm_optimizer_steps/input.yul":98:163   */
+  dataSize(sub_0)
+  dataOffset(sub_0)
+    /* "strict_asm_optimizer_steps/input.yul":107:108   */
+  0x00
+    /* "strict_asm_optimizer_steps/input.yul":98:163   */
+  codecopy
+    /* "strict_asm_optimizer_steps/input.yul":172:207   */
+  dataSize(sub_0)
+    /* "strict_asm_optimizer_steps/input.yul":179:180   */
+  0x00
+    /* "strict_asm_optimizer_steps/input.yul":172:207   */
+  return
+stop
+
+sub_0: assembly {
+        /* "strict_asm_optimizer_steps/input.yul":298:301   */
+      0x80
+        /* "strict_asm_optimizer_steps/input.yul":294:296   */
+      0x40
+        /* "strict_asm_optimizer_steps/input.yul":287:302   */
+      mstore
+        /* "strict_asm_optimizer_steps/input.yul":348:349   */
+      0x04
+        /* "strict_asm_optimizer_steps/input.yul":332:346   */
+      calldatasize
+        /* "strict_asm_optimizer_steps/input.yul":329:350   */
+      lt
+        /* "strict_asm_optimizer_steps/input.yul":322:351   */
+      iszero
+        /* "strict_asm_optimizer_steps/input.yul":319:321   */
+      pop
+        /* "strict_asm_optimizer_steps/input.yul":570:571   */
+      0x00
+        /* "strict_asm_optimizer_steps/input.yul":567:568   */
+      0x00
+        /* "strict_asm_optimizer_steps/input.yul":560:572   */
+      revert
+}

tools/yulPhaser/README.md

@@ -9,7 +9,7 @@ The input is a set of one or more [Yul](/docs/yul.rst) programs and each sequenc
 Optimised programs are given numeric scores according to the selected metric.
 
 Optimisation step sequences are presented in an abbreviated form - as strings of letters where each character represents one step.
-The abbreviations are defined in [`OptimiserSuite::stepNameToAbbreviationMap()`](/libyul/optimiser/Suite.cpp#L388-L423).
+There's a [table listing available abbreviations in the optimiser docs](/docs/yul.rst#optimization-step-sequence).
 
 ### How to use it
 The application has sensible defaults for most parameters.
@@ -66,14 +66,18 @@ tools/yul-phaser *.yul                    \
 `yul-phaser` can process the intermediate representation produced by `solc`:
 
 ``` bash
-solc/solc <sol file>  \
-    --ir              \
-    --no-optimize-yul \
-    --output-dir <output directory>
+solc/solc <sol file> --ir --output-dir <output directory>
 ```
 
 After running this command you'll find one or more .yul files in the output directory.
-These files contain whole Yul objects rather than just raw Yul programs but `yul-phaser` is prepared to handle them.
+These files contain whole Yul objects rather than just raw Yul programs but `yul-phaser` is prepared to handle them too.
+
+#### Using optimisation step sequences with the compiler
+You can tell Yul optimiser to use a specific sequence for your code by passing `--yul-optimizations` option to `solc`:
+
+``` bash
+solc/solc <sol file> --optimize --ir-optimized --yul-optimizations <sequence>
+```
 
 ### How to choose good parameters
 Choosing good parameters for a genetic algorithm is not a trivial task but phaser's defaults are generally enough to find a sequence that gives results comparable or better than one hand-crafted by an experienced developer for a given set of programs.