Prune unreferenced functions from CFG

ethereum · Dec 17, 2024 · 682d2c6 · 682d2c6
1 parent 03e2739
commit 682d2c6
Show file tree

Hide file tree

Showing 7 changed files with 203 additions and 3 deletions.
diff --git a/libyul/backends/evm/ControlFlowGraphBuilder.cpp b/libyul/backends/evm/ControlFlowGraphBuilder.cpp
@@ -52,12 +52,23 @@ namespace
 /// Removes edges to blocks that are not reachable.
 void cleanUnreachable(CFG& _cfg)
 {
+	// If operation is a function call it adds the callee entry as child
+	auto const addFunctionsEntries = [&_cfg](CFG::BasicBlock* _node, auto&& _addChild)
+	{
+		for (auto const& operation: _node->operations)
+		{
+			if (auto const* functionCall = std::get_if<CFG::FunctionCall>(&operation.operation))
+			{
+				auto const functionInfo = _cfg.functionInfo.at(&(functionCall->function.get()));
+				_addChild(functionInfo.entry);
+			}
+		}
+	};
+
 	// Determine which blocks are reachable from the entry.
 	util::BreadthFirstSearch<CFG::BasicBlock*> reachabilityCheck{{_cfg.entry}};
-	for (auto const& functionInfo: _cfg.functionInfo | ranges::views::values)
-		reachabilityCheck.verticesToTraverse.emplace_back(functionInfo.entry);
-
 	reachabilityCheck.run([&](CFG::BasicBlock* _node, auto&& _addChild) {
+		addFunctionsEntries(_node, _addChild);
 		visit(util::GenericVisitor{
 			[&](CFG::BasicBlock::Jump const& _jump) {
 				_addChild(_jump.target);
@@ -77,6 +88,16 @@ void cleanUnreachable(CFG& _cfg)
 		cxx20::erase_if(node->entries, [&](CFG::BasicBlock* entry) -> bool {
 			return !reachabilityCheck.visited.count(entry);
 		});
+
+	// Remove functions which are never referenced.
+	_cfg.functions.erase(std::remove_if(_cfg.functions.begin(), _cfg.functions.end(), [&](auto const& item) {
+		return !reachabilityCheck.visited.count(_cfg.functionInfo.at(item).entry);
+	}), _cfg.functions.end());
+
+	// Remove functionInfos which are never referenced.
+	cxx20::erase_if(_cfg.functionInfo, [&](auto const& entry) -> bool {
+		return !reachabilityCheck.visited.count(entry.second.entry);
+	});
 }
 
 /// Sets the ``recursive`` member to ``true`` for all recursive function calls.

diff --git a/test/libyul/objectCompiler/eof/prune_unreachable_function_non_returning.yul b/test/libyul/objectCompiler/eof/prune_unreachable_function_non_returning.yul
@@ -0,0 +1,29 @@
+object "Contract" {
+    code {
+        f()
+        g()
+
+        function f() { revert(0, 0) }
+        function g() { mstore(0, 2) }
+    }
+}
+
+// ====
+// EVMVersion: >=shanghai
+// bytecodeFormat: >=EOFv1
+// optimizationPreset: none
+// ----
+// Assembly:
+//     /* "source":53:56   */
+//   jumpf{code_section_1}
+//
+// code_section_1: assembly {
+//         /* "source":124:125   */
+//       0x00
+//         /* "source":114:126   */
+//       dup1
+//       revert
+// }
+// Bytecode: ef000101000802000200030003040000000080ffff0080ffffe500015f80fd
+// Opcodes: 0xEF STOP ADD ADD STOP ADDMOD MUL STOP MUL STOP SUB STOP SUB DIV STOP STOP STOP STOP DUP1 SELFDESTRUCT SELFDESTRUCT STOP DUP1 SELFDESTRUCT SELFDESTRUCT JUMPF 0x1 PUSH0 DUP1 REVERT
+// SourceMappings: 53:3:0:i:0124:1:0:-:0;114:12;
diff --git a/test/libyul/objectCompiler/eof/prune_unreachable_function_recursion.yul b/test/libyul/objectCompiler/eof/prune_unreachable_function_recursion.yul
@@ -0,0 +1,26 @@
+object "Contract" {
+    code {
+        f()
+        g()
+
+        function f() { f() }
+        function g() { mstore(0, 2) }
+    }
+}
+
+// ====
+// EVMVersion: >=shanghai
+// bytecodeFormat: >=EOFv1
+// optimizationPreset: none
+// ----
+// Assembly:
+//     /* "source":53:56   */
+//   jumpf{code_section_1}
+//
+// code_section_1: assembly {
+//         /* "source":114:117   */
+//       jumpf{code_section_1}
+// }
+// Bytecode: ef000101000802000200030003040000000080ffff0080ffffe50001e50001
+// Opcodes: 0xEF STOP ADD ADD STOP ADDMOD MUL STOP MUL STOP SUB STOP SUB DIV STOP STOP STOP STOP DUP1 SELFDESTRUCT SELFDESTRUCT STOP DUP1 SELFDESTRUCT SELFDESTRUCT JUMPF 0x1 JUMPF 0x1
+// SourceMappings: 53:3:0:i:0114:3:0:i:0
diff --git a/test/libyul/objectCompiler/eof/prune_unreferenced_function.yul b/test/libyul/objectCompiler/eof/prune_unreferenced_function.yul
@@ -0,0 +1,33 @@
+object "Contract" {
+    code {
+        g()
+
+        function f() { mstore(0, 3) }
+        function g() { mstore(0, 2) }
+    }
+}
+
+// ====
+// EVMVersion: >=shanghai
+// bytecodeFormat: >=EOFv1
+// optimizationPreset: none
+// ----
+// Assembly:
+//     /* "source":41:44   */
+//   callf{code_section_1}
+//     /* "source":29:98   */
+//   stop
+//
+// code_section_1: assembly {
+//         /* "source":88:89   */
+//       0x02
+//         /* "source":85:86   */
+//       0x00
+//         /* "source":78:90   */
+//       mstore
+//         /* "source":55:92   */
+//       retf
+// }
+// Bytecode: ef000101000802000200040005040000000080ffff0000ffffe300010060025f52e4
+// Opcodes: 0xEF STOP ADD ADD STOP ADDMOD MUL STOP MUL STOP DIV STOP SDIV DIV STOP STOP STOP STOP DUP1 SELFDESTRUCT SELFDESTRUCT STOP STOP SELFDESTRUCT SELFDESTRUCT CALLF 0x1 STOP PUSH1 0x2 PUSH0 MSTORE RETF
+// SourceMappings: 41:3:0:i:0;29:69::-88:1:0:-:0;85;78:12;55:37::o
diff --git a/test/libyul/objectCompiler/prune_unreachable_function_non_returning.yul b/test/libyul/objectCompiler/prune_unreachable_function_non_returning.yul
@@ -0,0 +1,29 @@
+object "Contract" {
+    code {
+        f()
+        g()
+
+        function f() { revert(0, 0) }
+        function g() { mstore(0, 2) }
+    }
+}
+
+// ====
+// EVMVersion: >=shanghai
+// bytecodeFormat: legacy
+// optimizationPreset: none
+// ----
+// Assembly:
+//     /* "source":53:56   */
+//   tag_1
+//   jump	// in
+//     /* "source":91:128   */
+// tag_1:
+//     /* "source":124:125   */
+//   0x00
+//     /* "source":114:126   */
+//   dup1
+//   revert
+// Bytecode: 6003565b5f80fd
+// Opcodes: PUSH1 0x3 JUMP JUMPDEST PUSH0 DUP1 REVERT
+// SourceMappings: 53:3:0:-:0;:::i;91:37::-;124:1;114:12;
diff --git a/test/libyul/objectCompiler/prune_unreachable_function_recursion.yul b/test/libyul/objectCompiler/prune_unreachable_function_recursion.yul
@@ -0,0 +1,27 @@
+object "Contract" {
+    code {
+        f()
+        g()
+
+        function f() { f() }
+        function g() { mstore(0, 2) }
+    }
+}
+
+// ====
+// EVMVersion: >=shanghai
+// bytecodeFormat: legacy
+// optimizationPreset: none
+// ----
+// Assembly:
+//     /* "source":53:56   */
+//   tag_1
+//   jump	// in
+//     /* "source":91:119   */
+// tag_1:
+//     /* "source":114:117   */
+//   tag_1
+//   jump	// in
+// Bytecode: 6003565b600356
+// Opcodes: PUSH1 0x3 JUMP JUMPDEST PUSH1 0x3 JUMP
+// SourceMappings: 53:3:0:-:0;:::i;91:28::-;114:3;:::i
diff --git a/test/libyul/objectCompiler/prune_unreferenced_function.yul b/test/libyul/objectCompiler/prune_unreferenced_function.yul
@@ -0,0 +1,35 @@
+object "Contract" {
+    code {
+        g()
+
+        function f() { mstore(0, 3) }
+        function g() { mstore(0, 2) }
+    }
+}
+
+// ====
+// EVMVersion: >=shanghai
+// bytecodeFormat: legacy
+// optimizationPreset: none
+// ----
+// Assembly:
+//     /* "source":41:44   */
+//   tag_2
+//   tag_1
+//   jump	// in
+// tag_2:
+//     /* "source":29:98   */
+//   stop
+//     /* "source":55:92   */
+// tag_1:
+//     /* "source":88:89   */
+//   0x02
+//     /* "source":85:86   */
+//   0x00
+//     /* "source":78:90   */
+//   mstore
+//     /* "source":55:92   */
+//   jump	// out
+// Bytecode: 60056007565b005b60025f5256
+// Opcodes: PUSH1 0x5 PUSH1 0x7 JUMP JUMPDEST STOP JUMPDEST PUSH1 0x2 PUSH0 MSTORE JUMP
+// SourceMappings: 41:3:0:-:0;;:::i;:::-;29:69;55:37;88:1;85;78:12;55:37::o