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Does GCC optimize assembly?
No. GCC passes your assembly source through the preprocessor and then to the assembler. At no time are any optimisations performed. If you don’t want to hand-optimize your asm, assembly language is the wrong choice of source language for you.
Is GCC an optimizing compiler?
GCC performs nearly all supported optimizations that do not involve a space-speed tradeoff. It also enables -finline-functions , causes the compiler to tune for code size rather than execution speed, and performs further optimizations designed to reduce code size.
What optimization does GCC do?
The compiler optimizes to reduce the size of the binary instead of execution speed. If you do not specify an optimization option, gcc attempts to reduce the compilation time and to make debugging always yield the result expected from reading the source code.
Does GCC optimize by default?
-O0 or no -O option (default) At this optimization level GCC does not perform any optimization and compiles the source code in the most straightforward way possible. Each command in the source code is converted directly to the corresponding instructions in the executable file, without rearrangement.
What to do when optimization is not turned on in GCC?
Emit variables declared static const when optimization isn’t turned on, even if the variables aren’t referenced. GCC enables this option by default. If you want to force the compiler to check if a variable is referenced, regardless of whether or not optimization is turned on, use the -fno-keep-static-consts option.
Which is the default option for the GCC compiler?
At levels -O1 and higher, -fdefer-pop is the default; this allows the compiler to let arguments accumulate on the stack for several function calls and pop them all at once. Perform a forward propagation pass on RTL. The pass tries to combine two instructions and checks if the result can be simplified.
Which is compiler option enables all O2 optimizations?
-Os enables all -O2 optimizations except those that often increase code size: It also enables -finline-functions, causes the compiler to tune for code size rather than execution speed, and performs further optimizations designed to reduce code size. Disregard strict standards compliance. -Ofast enables all -O3 optimizations.
Which is the optimize option in GCC for Fortran?
-Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard-compliant programs. It turns on -ffast-math, -fallow-store-data-races and the Fortran-specific -fstack-arrays, unless -fmax-stack-var-size is specified, and -fno-protect-parens .