eth-janishutz/eth-summaries
1
0
Fork 0
mirror of https://github.com/janishutz/eth-summaries.git synced 2026-01-13 02:38:25 +00:00
Code Issues Packages Projects Releases Wiki Activity

[SPCA] Stack

Browse Source 
almost complete, still missing variadic functions
This commit is contained in:
Janis Hutz
2026-01-12 08:06:51 +01:00
parent 53c5e984b2
commit 639c147264
4 changed files with 65 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
semester3/spca/parts/00_asm/04_control-flow.tex
View File

@@ -3,7 +3,8 @@
Control flow structures from \verb|C| like \verb|if/else| or \verb|for| are compiled into assembly mainly using jumps and conditional \verb|move|.
By the nature of Assembly and thanks to compilers optimizing aggressively, there is no \textit{single} definitive translation of the \verb|C| control structures: The compiler may translate it very differently depending on the context of the program.
By the nature of Assembly and thanks to compilers optimizing aggressively, there is no \textit{single} definitive translation of the \verb|C| control structures:
The compiler may translate it very differently depending on the context of the program.
\subsubsection{Conditional statements}
A function using an \verb|if/else| construct to choose the maximum of $2$ numbers might compile like this:
@@ -30,4 +31,9 @@ The same function, using a \verb|while| loop instead may lead to this:
\verb|for| loops follow the same idea as \verb|while| loops, albeit with a few more jumps.
\verb|switch| statements are implemented differently depending on size and case values: Sparse switch statements are compiled as decision trees, whereas large switch statements may become \textit{jump tables}.
\verb|switch| statements are implemented differently depending on size and case values:
Sparse switch statements are compiled as decision trees, whereas large switch statements may become \textit{jump tables}.
These jump tables are usually stored in the \texttt{.rodata} section with 8-byte alignment. The jump uses offsets:
\mint{asm}|jmp *.LABEL(, %rsi, 8)|
and we jump to the effective address of \texttt{.LABEL + rsi * 8}