Remove swap after dup.

Changelog.md

@@ -10,6 +10,7 @@ Bugfixes:
 Compiler Features:
  * Build System: Update internal dependency of jsoncpp to 1.9.3.
  * Optimizer: Add rule to remove shifts inside the byte opcode.
+ * Peephole Optimizer: Add rule to remove swap after dup.
 
 
 ### 0.6.11 (2020-07-07)

libevmasm/PeepholeOptimiser.cpp

@@ -205,6 +205,30 @@ struct SwapComparison: SimplePeepholeOptimizerMethod<SwapComparison, 2>
 	}
 };
 
+/// Remove swapN after dupN
+struct DupSwap: SimplePeepholeOptimizerMethod<DupSwap, 2>
+{
+	static size_t applySimple(
+		AssemblyItem const& _dupN,
+		AssemblyItem const& _swapN,
+		std::back_insert_iterator<AssemblyItems> _out
+	)
+	{
+		if (
+			SemanticInformation::isDupInstruction(_dupN) &&
+			SemanticInformation::isSwapInstruction(_swapN) &&
+			getDupNumber(_dupN.instruction()) == getSwapNumber(_swapN.instruction())
+		)
+		{
+			*_out = _dupN;
+			return true;
+		}
+		else
+			return false;
+	}
+};
+
+
 struct IsZeroIsZeroJumpI: SimplePeepholeOptimizerMethod<IsZeroIsZeroJumpI, 4>
 {
 	static size_t applySimple(
@@ -357,7 +381,7 @@ bool PeepholeOptimiser::optimise()
 		applyMethods(
 			state,
 			PushPop(), OpPop(), DoublePush(), DoubleSwap(), CommutativeSwap(), SwapComparison(),
-			IsZeroIsZeroJumpI(), JumpToNext(), UnreachableCode(),
+			DupSwap(), IsZeroIsZeroJumpI(), JumpToNext(), UnreachableCode(),
 			TagConjunctions(), TruthyAnd(), Identity()
 		);
 	if (m_optimisedItems.size() < m_items.size() || (

test/cmdlineTests/dup_opt_peephole/args

@@ -0,0 +1 @@
+--asm

test/cmdlineTests/dup_opt_peephole/err

@@ -0,0 +1,5 @@
+Warning: SPDX license identifier not provided in source file. Before publishing, consider adding a comment containing "SPDX-License-Identifier: <SPDX-License>" to each source file. Use "SPDX-License-Identifier: UNLICENSED" for non-open-source code. Please see https://spdx.org for more information.
+--> dup_opt_peephole/input.sol
+
+Warning: Source file does not specify required compiler version!
+--> dup_opt_peephole/input.sol

test/cmdlineTests/dup_opt_peephole/input.sol

@@ -0,0 +1,9 @@
+contract C {
+	fallback() external {
+		assembly {
+			let x := calldataload(0)
+			x := x
+			sstore(0, x)
+		}
+	}
+}

test/cmdlineTests/dup_opt_peephole/output

@@ -0,0 +1,54 @@
+
+======= dup_opt_peephole/input.sol:C =======
+EVM assembly:
+    /* "dup_opt_peephole/input.sol":0:111  contract C {... */
+  mstore(0x40, 0x80)
+  callvalue
+  dup1
+  iszero
+  tag_1
+  jumpi
+  0x00
+  dup1
+  revert
+tag_1:
+  pop
+  dataSize(sub_0)
+  dup1
+  dataOffset(sub_0)
+  0x00
+  codecopy
+  0x00
+  return
+stop
+
+sub_0: assembly {
+        /* "dup_opt_peephole/input.sol":0:111  contract C {... */
+      mstore(0x40, 0x80)
+      callvalue
+      dup1
+      iszero
+      tag_3
+      jumpi
+      0x00
+      dup1
+      revert
+    tag_3:
+      pop
+        /* "dup_opt_peephole/input.sol":74:75  0 */
+      0x00
+        /* "dup_opt_peephole/input.sol":61:76  calldataload(0) */
+      calldataload
+        /* "dup_opt_peephole/input.sol":100:101  x */
+      dup1
+        /* "dup_opt_peephole/input.sol":97:98  0 */
+      0x00
+        /* "dup_opt_peephole/input.sol":90:102  sstore(0, x) */
+      sstore
+        /* "dup_opt_peephole/input.sol":47:106  {... */
+      pop
+        /* "dup_opt_peephole/input.sol":0:111  contract C {... */
+      stop
+
+    auxdata: AUXDATA REMOVED
+}