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GCC and Clang can be made to use a similar calling convention by using __stdcall with the regparm function attribute or the -mregparm=3 switch. (The stack order is inverted.) It is also possible to produce a caller clean-up variant using cdecl or extend this to also use SSE registers. [18]
GCC and clang requires explicit target_clones labels in the code to "clone" functions, [20] while ICC does so automatically (under the command-line option /Qax). The Rust programming language also supports FMV. The setup is similar to GCC and Clang in that the code defines what instruction sets to compile for, but cloning is manually done via ...
clang and gcc have varying default states depending on platform and optimization level. A non-C99-compliant method of enabling the DAZ and FTZ flags on targets supporting SSE is given below, but is not widely supported. It is known to work on Mac OS X since at least 2006. [12]
AMD was the first to introduce the instructions that now form Intel's BMI1 as part of its ABM (Advanced Bit Manipulation) instruction set, then later added support for Intel's new BMI2 instructions.
The additional downclocking is triggered by the 512-bit width of vectors and depends on the nature of instructions being executed; using the 128 or 256-bit part of AVX-512 (AVX-512VL) does not trigger it. As a result, gcc and clang default to prefer using the 256-bit vectors for Intel targets. [40] [41] [42]
In practice, Clang is a drop-in replacement for GCC. [24] Clang's developers aim to reduce memory footprint and increase compiling speed compared to other compilers, such as GCC. In October 2007, they report that Clang compiled the Carbon libraries more than twice as fast as GCC, while using about one-sixth GCC's memory and disk space. [25]
GNAT (Ada language frontend of the GCC suite), and LLVM uses the GCC syntax. [9] [10] The D programming language uses a DSL similar to the MSVC extension officially for x86_64, [11] but the LLVM-based LDC also provides the GCC-style syntax on every architecture. [12] MSVC only supports inline assembler on 32-bit x86. [5]
Intrinsic functions are often used to explicitly implement vectorization and parallelization in languages which do not address such constructs. Some application programming interfaces (API), for example, AltiVec and OpenMP, use intrinsic functions to declare, respectively, vectorizable and multiprocessing-aware operations during compiling.