Use STATICCALL for pure function calls if EVM version supports it and 0.5.0 is activated.

3 files changed, 13 insertions, 3 deletions

diff --git a/Changelog.md b/Changelog.md
index bea9dd5b..4a9f7ff4 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -2,8 +2,9 @@
 
 Features:
  * C99/C++-style scoping rules (instead of JavaScript function scoping) take effect as experimental v0.5.0 feature.
- * Code Generator: Assert that ``k != 0`` for ``molmod(a, b, k)`` and ``addmod(a, b, k)`` as experimental 0.5.0 feature.
+ * Code Generator: Assert that ``k != 0`` for ``mulmod(a, b, k)`` and ``addmod(a, b, k)`` as experimental 0.5.0 feature.
  * Code Generator: Do not retain any gas in calls (except if EVM version is set to homestead).
+ * Code Generator: Use ``STATICCALL`` opcode for calling ``view`` and ``pure`` functions as experimenal 0.5.0 feature.
  * Interface: Provide ability to select target EVM version (homestead or byzantium, with byzantium being the default).
  * Standard JSON: Reject badly formatted invalid JSON inputs.
  * Type Checker: Disallow uninitialized storage pointers as experimental 0.5.0 feature.
diff --git a/libsolidity/ast/ExperimentalFeatures.h b/libsolidity/ast/ExperimentalFeatures.h
index a17778b4..30ea7ec5 100644
--- a/libsolidity/ast/ExperimentalFeatures.h
+++ b/libsolidity/ast/ExperimentalFeatures.h
@@ -29,8 +29,8 @@ namespace solidity
 
 enum class ExperimentalFeature
 {
-	SMTChecker,
 	ABIEncoderV2, // new ABI encoder that makes use of JULIA
+	SMTChecker,
 	V050, // v0.5.0 breaking changes
 	Test,
 	TestOnlyAnalysis
@@ -45,8 +45,8 @@ static const std::map<ExperimentalFeature, bool> ExperimentalFeatureOnlyAnalysis
 
 static const std::map<std::string, ExperimentalFeature> ExperimentalFeatureNames =
 {
-	{ "SMTChecker", ExperimentalFeature::SMTChecker },
 	{ "ABIEncoderV2", ExperimentalFeature::ABIEncoderV2 },
+	{ "SMTChecker", ExperimentalFeature::SMTChecker },
 	{ "v0.5.0", ExperimentalFeature::V050 },
 	{ "__test", ExperimentalFeature::Test },
 	{ "__testOnlyAnalysis", ExperimentalFeature::TestOnlyAnalysis },
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index d27af7db..7162cb0d 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -1610,6 +1610,10 @@ void ExpressionCompiler::appendExternalFunctionCall(
 	bool returnSuccessCondition = funKind == FunctionType::Kind::BareCall || funKind == FunctionType::Kind::BareCallCode || funKind == FunctionType::Kind::BareDelegateCall;
 	bool isCallCode = funKind == FunctionType::Kind::BareCallCode || funKind == FunctionType::Kind::CallCode;
 	bool isDelegateCall = funKind == FunctionType::Kind::BareDelegateCall || funKind == FunctionType::Kind::DelegateCall;
+	bool useStaticCall =
+		_functionType.stateMutability() <= StateMutability::View &&
+		m_context.experimentalFeatureActive(ExperimentalFeature::V050) &&
+		m_context.evmVersion().hasStaticCall();
 
 	unsigned retSize = 0;
 	if (returnSuccessCondition)
@@ -1738,6 +1742,8 @@ void ExpressionCompiler::appendExternalFunctionCall(
 	// [value,] addr, gas (stack top)
 	if (isDelegateCall)
 		solAssert(!_functionType.valueSet(), "Value set for delegatecall");
+	else if (useStaticCall)
+		solAssert(!_functionType.valueSet(), "Value set for staticcall");
 	else if (_functionType.valueSet())
 		m_context << dupInstruction(m_context.baseToCurrentStackOffset(valueStackPos));
 	else
@@ -1769,10 +1775,13 @@ void ExpressionCompiler::appendExternalFunctionCall(
 			gasNeededByCaller += eth::GasCosts::callNewAccountGas; // we never know
 		m_context << gasNeededByCaller << Instruction::GAS << Instruction::SUB;
 	}
+	// Order is important here, STATICCALL might overlap with DELEGATECALL.
 	if (isDelegateCall)
 		m_context << Instruction::DELEGATECALL;
 	else if (isCallCode)
 		m_context << Instruction::CALLCODE;
+	else if (useStaticCall)
+		m_context << Instruction::STATICCALL;
 	else
 		m_context << Instruction::CALL;