Say I have a database looking like this; Product with columns [ProductName] [Price] [Misc] [Etc] Order with columns [OrderID] [ProductName] [Quantity] [Misc] [Etc] ProductName is primary key of Product, of some string type and unique. OrderID is primary key and of some integer type, and ProductName being a foreign key. Say I change ...
Suppose I've following Code: Console.WriteLine("Value1: " + SomeEnum.Value1.ToString() + "\r\nValue2: " + SomeOtherEnum.Value2.ToString()); Will Compiler Optimize this to: Console.WriteLine("Value1: " + SomeEnum.Value1 + "\r\nValue2: " + SomeOtherEnum.Value2); I've checked it with IL Di...
Hi, I recently rolled out a new Toolchain on Linux, with gcc 4.5.0 and binutils 2.20 with gold. Now I was curious about this new thing PGO. While it's clear how it works with executables, I've not been able to find an answer on shared libraries. I found two unanswered posts on the gcc mailing list via google, that's all. So here's what...
I'm using Rice to write a C++ extension for a Ruby gem. The extension is in the form of a shared object (.so) file. This requires 'mkmf-rice' instead of 'mkmf', but the two (AFAIK) are pretty similar. By default, the compiler uses the flags -g -O2. Personally, I find this kind of silly, since it's hard to debug with any optimization en...
Hello World! I am facing a rather peculiar problem. I am working on a compiler for an architecture that doesn't support bitwise operations. However, it handles signed 16 bit integer arithmetics and I was wondering if it would be possible to implement bitwise operations using only: Addition (c = a + b) Subtraction (c = a - b) Division...
A little test program: #include <iostream> const float TEST_FLOAT = 1/60; const float TEST_A = 1; const float TEST_B = 60; const float TEST_C = TEST_A / TEST_B; int main() { std::cout << TEST_FLOAT << std::endl; std::cout << TEST_C << std::endl; std::cin.ignore(); return 0; } Result : 0 0.0166667 Tested on Visual Studio 2...
I'm using and x86 based core to manipulate a 32-bit memory mapped register. My hardware behaves correctly only if the CPU generates 32-bit wide reads and writes to this register. The register is aligned on a 32-bit address and is not addressable at byte granularity. What can I do to guarantee that my C (or C99) compiler will only gene...
We have some code that looks like this: inline int calc_something(double x) { if (x > 0.0) { // do something return 1; } else { // do something else return 0; } } Unfortunately, when using the flag /fp:fast, we get calc_something(0)==1 so we are clearly taking the wrong code path. This only happens when we use th...
Can we see optimized code in c++.............(not assembly)?? ...
Documentation for __assume says "The most common use of __assume is with the default case of a switch statement, as shown in the following example.". Is there any other case where __assume can lead to a more efficient (or even a different) code? When inside of if / else , is compiler automatically "assuming" what is already know becau...
In Visual Studio C/C++ projects, it's easy to modify compiler's optimization settings in "Property Pages | C/C++ | Optimization". For example, we may give different optimization levels such as /O2 and /O3, as well as advanced optimizations like "Omit Frame Pointers". However, I can't simply find corresponding UIs in C# project of Visual...
Background: Many years ago, I inherited a codebase that was using the Visual Studio (VC++) flag '/fp:fast' to produce faster code in a particular calculation-heavy library. Unfortunately, '/fp:fast' produced results that were slightly different to the same library under a different compiler (Borland C++). As we needed to produce exactly...
Im just wondering how good the MSVC++ Compiler can optimize code(with Code examples) or what he can't optimize and why. For example i used the SSE-intrinsics with something like this(var is an __m128 value)(it was for an frustrum-culling test): if( var.m128_f32[0] > 0.0f && var.m128_f32[1] > 0.0f && var.m128_f32[2] > 0.0f && var.m128_f...
I'm trying to read an avi file in OpenCV 2.1, VS2008 standard for 2 days now with no luck. I constantly get this message in the program console: Compiler did not align stack variables. Libavcodec has been miscompiled and may be very slow or crash. This is not a bug in libavcodec, but in the compiler. You may try recompiling using...
OK OK, I know this is a hack, but this was for a tiny data-manipulation project and I wanted to play around. ;-) I was always under the impression that the compiler would examine all anonymous types used in a C# program and if the properties were the same, it would only create one class behind the scenes. So let's say I want to create ...
Below, the result1 and result2 variable values are reporting different values depending upon whether or not you compile the code with -g or with -O on GCC 4.2.1 and on GCC 3.2.0 (and I have not tried more recent GCC versions): double double_identity(double in_double) { return in_double; } ... double result1 = ceil(log(32.0) / log(...
Does the java compiler (the default javac that comes in JDK1.6.0_21) optimize code to prevent the same method from being called with the same arguments over and over? If I wrote this code: public class FooBar { public static void main(String[] args) { foo(bar); foo(bar); foo(bar); } } Would the method f...
I need to pass a "General Compiler Design" test from a potential employer and believe the best way to do so would be to get to know a little about all of compiler design. If you think another method would be better, let me know. Now then: I have intermediate to advanced knowledge of: C C++ (not as much as C) C# Java Python Ruby Perl PH...
Hello, i'm writting handler for OpenGL texture and i'm thinking about safety and performance. Which level of optimization should remove marked if statements? struct Texture2D { GLuint ID; inline Texture2D(): ID(0) {}; inline explicit Texture2D(GLuint id): ID(id) {}; ~Texture2D(); void GenTexture(bool regen = false...
Hello, I'm trying to learn how to reverse engineer software and all the tricks to understand how the code looks like before the compiler optimizations. I found something like this several times: if (a < 0) a = -2147483648 - a; I originally thought it was an abs(): a underflows so you get the positive value. But since a is n...