From 058d9a952a3ede95d2617b98e8dd669938d22463 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pawe=C5=82=20Bylica?= <chfast@gmail.com>
Date: Tue, 13 Aug 2019 19:46:05 +0200
Subject: [PATCH] Do not keep information about block stack change

This information is only needed in analysis to compute other block stack requirements parameters.
---
 lib/evmone/analysis.cpp          | 8 +++++---
 lib/evmone/analysis.hpp          | 1 -
 test/unittests/analysis_test.cpp | 2 --
 test/utils/dump.cpp              | 2 +-
 4 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/lib/evmone/analysis.cpp b/lib/evmone/analysis.cpp
index 4a4046eafe..f8b13843b2 100644
--- a/lib/evmone/analysis.cpp
+++ b/lib/evmone/analysis.cpp
@@ -54,6 +54,7 @@ code_analysis analyze(
 
     block_info* block = nullptr;
 
+    int block_stack_change = 0;
     int instr_index = 0;
 
     const auto code_end = code + code_size;
@@ -68,6 +69,7 @@ code_analysis analyze(
         {
             // Create new block.
             block = &analysis.blocks.emplace_back();
+            block_stack_change = 0;
 
             // Create BEGINBLOCK instruction which either replaces JUMPDEST or is injected
             // in case there is no JUMPDEST.
@@ -89,9 +91,9 @@ code_analysis analyze(
         const auto instr_stack_req = metrics.num_stack_arguments;
         const auto instr_stack_change = metrics.num_stack_returned_items - instr_stack_req;
 
-        block->stack_req = std::max(block->stack_req, instr_stack_req - block->stack_change);
-        block->stack_change += instr_stack_change;
-        block->stack_max = std::max(block->stack_max, block->stack_change);
+        block->stack_req = std::max(block->stack_req, instr_stack_req - block_stack_change);
+        block_stack_change += instr_stack_change;
+        block->stack_max = std::max(block->stack_max, block_stack_change);
 
         if (metrics.gas_cost > 0)  // can be -1 for undefined instruction
             block->gas_cost += metrics.gas_cost;
diff --git a/lib/evmone/analysis.hpp b/lib/evmone/analysis.hpp
index 6195e47ceb..c56ce234af 100644
--- a/lib/evmone/analysis.hpp
+++ b/lib/evmone/analysis.hpp
@@ -165,7 +165,6 @@ struct block_info
     int64_t gas_cost = 0;
     int stack_req = 0;     ///< The required stack height to execute the block.
     int stack_max = 0;     ///< The relative maximum stack height in the block.
-    int stack_change = 0;  ///< The relative stack height change after the execution of the block.
 };
 
 struct code_analysis
diff --git a/test/unittests/analysis_test.cpp b/test/unittests/analysis_test.cpp
index 1172ff4f84..b450f5c752 100644
--- a/test/unittests/analysis_test.cpp
+++ b/test/unittests/analysis_test.cpp
@@ -43,7 +43,6 @@ TEST(analysis, example1)
     EXPECT_EQ(analysis.blocks[0].gas_cost, 14);
     EXPECT_EQ(analysis.blocks[0].stack_req, 0);
     EXPECT_EQ(analysis.blocks[0].stack_max, 2);
-    EXPECT_EQ(analysis.blocks[0].stack_change, 0);
 }
 
 TEST(analysis, stack_up_and_down)
@@ -63,7 +62,6 @@ TEST(analysis, stack_up_and_down)
     EXPECT_EQ(analysis.blocks[0].gas_cost, 7 * 3 + 10 * 2 + 3);
     EXPECT_EQ(analysis.blocks[0].stack_req, 3);
     EXPECT_EQ(analysis.blocks[0].stack_max, 7);
-    EXPECT_EQ(analysis.blocks[0].stack_change, -2);
 }
 
 TEST(analysis, push)
diff --git a/test/utils/dump.cpp b/test/utils/dump.cpp
index ce5113d1bc..e7d331f0f2 100644
--- a/test/utils/dump.cpp
+++ b/test/utils/dump.cpp
@@ -48,7 +48,7 @@ void dump_analysis(const evmone::code_analysis& analysis)
                 std::cout << "  ";
 
             std::cout << " " << std::setw(10) << block->gas_cost << " " << block->stack_req << " "
-                      << block->stack_max << " " << block->stack_change << "\n";
+                      << block->stack_max << "\n";
         }
 
         std::cout << "│ " << std::setw(9) << std::left << name << std::setw(4) << std::right