В IAR стандартный float IEEE-754 http://www.iar.com/en/Products/IAR-Embedded-Workbench/Technology/Language-standards/
http://www.iar.com/en/Products/IAR-Embedded-Workbench/Technology/Components/
Language and standards
The C programming language as standardized by ISO/ANSI C99
Full support for C++
Full Embedded C++ library containing string, streams etc., as well as the Standard Template Library (STL)
IEEE-754 floating-point arithmetic
MISRA C checker (2004 & 1998) for code quality control
Support for a wide range of industry-standard debug and image formats, compatible with most popular debuggers and emulators, including ELF/DWARF where applicable