A jump table (also known as a branch table) is used to transfer program control (branching) to another part of the program by storing a table of branch instructions.
Questions tagged [jump-table]
63 questions
282
votes
12 answers
Is 'switch' faster than 'if'?
Is a switch statement actually faster than an if statement?
I ran the code below on Visual Studio 2010's x64 C++ compiler with the /Ox flag:
#include
#include
#include
#define MAX_COUNT (1 << 29)
size_t counter =…
user541686
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24
votes
11 answers
How to store goto labels in an array and then jump to them?
I want to declare an array of "jumplabels".
Then I want to jump to a "jumplabel" in this array.
But I have not any idea how to do this.
It should look like the following code:
function()
{
"gotolabel" s[3];
s[0] = s0;
s[1] = s1;
s[2]…
youllknow
11
votes
7 answers
Does "default" switch case disturb jump table optimization?
In my code I'm used to write fall-back default cases containing asserts like the following, to guard me against forgetting to update the switch in case semantics change
switch(mode) {
case ModeA: ... ;
case ModeB: ... ;
case .. /* many of them ...…
Johannes Schaub - litb
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11
votes
2 answers
c switch and jump tables
It is my understanding that a switch statement in c/c++ will sometimes compile to a jump table.
My question is, are there any thumb rules to assure that?
In my case I'm doing something like this:
enum myenum{
MY_CASE0= 0,
MY_CASE0= 1,…
Daniel Miron
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8
votes
3 answers
jump table examples in C
Please give me some examples of jump table usage. I have seen this example on wikipedia:
#include
#include
typedef void (*Handler)(void); /* A pointer to a handler function */
/* The functions */
void func3 (void) {…
user1128265
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7
votes
1 answer
How can I dynamically hint a branch target to an x64 CPU?
I'd like to know how to write efficient jump tables for x64 processors, either in C, C++ or assembly. The input is known in advance, but impossible to predict algorithmically. Assuming I can look as far ahead as I want in the input stream, is…
Nathan Kurz
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6
votes
2 answers
Get a label address out of the function scope in gcc/clang (C++)
I'm making some kind of interpreter and I'm computing a static const jump table thanks to local label addresses.
You know the drill,
static const int JUMP_TABLE[] = { &&case0 - &&case0, &&case1 - &&case0 and so on.
For various reasons, mostly…
Tramboi
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6
votes
9 answers
Is there anything like branch/jump table in Java?
Does Java have something similar to a branch or jump table?
A branch or jump table table is, according to wikipedia,
a term used to describe an efficient method of transferring program control (branching) to another part of a program (or a…
jbu
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6
votes
2 answers
Switch-Case: declaration-with-initialization & declaration-and-then-assignment
In the switch-case statements declaration-with-initialization is invalid but declaration-and-then-assignment is allowed. As shown in the following code snippet.
What is difference between these two type of initializations from the compiler side?…
Manjeet Dahiya
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5
votes
1 answer
Convert x86 Assembly Jump Table to C
I have this x86 assembly code and I'm trying to convert it to C:
.GLOBAL calculate
calculate:
pushl %ebp
movl %esp,%ebp
movl 12(%ebp),%eax
movl 8(%ebp),%ecx
cmpl $2,%ecx
ja done
jmp *operations(,%ecx,4)
operation1:
…
Benck
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5
votes
1 answer
Switch statement without jump table
Is it possible to use a switch statement without a jump table? GCC creates stupid (and in my case unusable) jump tables which I want to avoid.
kaetzacoatl
- 1,419
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4
votes
4 answers
"Local" labels in C and jump table implementation
I'm trying to make a macro-based jump table in C.
Here's some example code:
#include "stdio.h"
#define GOTO(X) static void* caseArg[] = {&&I0, &&R0, &&S0, &&F0, &&G0, &&H0}; \
goto *caseArg[X];
#define FINISH() goto caseEnd;
int main(int…
Dr.Kameleon
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4
votes
0 answers
Why JavaScript doesn't implement jump table for its switch statement?
Hello I've read this in a book,
The fact that the case expressions are evaluated at run-time makes the JavaScript switch statement much
different from (and less efficient than) the switch statement of C, C++, and Java. In those languages, the
…
Nour El-Deen Abou El-Kassem
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4
votes
1 answer
Strategies to develop STM32 in application programming
I'm looking for ideas about how to develop a In Application Programming module.
We've developed in "C" a STM32F2xx connection box for our android system. In essence this is only an multi-device to bluetooth information bridge. Now I'm thinking in…
rpr
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4
votes
4 answers
Implementing a Jump Table in Java
How do I make the switch/case statement in this simple Calculator program into a jump table.
import java.lang.*;
import java.util.*;
public class Calculator
{
private int solution;
private static int x, y, ops;
private char operators;
…
Richie Miz
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