AN720 データシートの表示（PDF） - Silicon Laboratories

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AN720

PRECISION32 OPTIMIZATIONCONSIDERATIONS FOR CODESIZE ANDSPEED

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AN720

5.3. Toolchain Library Usage

Some toolchains have multiple libraries or settings that can change the size or execution speed of code. The

Precision32 tools have six options:

newlib (standard GCC) with no standard I/O

newlib (standard GCC) with nohosting standard I/O

newlib (standard GCC) with semihosting standard I/O

redlib (GCC) with no standard I/O

redlib (GCC) with nohosting standard I/O

redlib (GCC) with semihosting standard I/O

The semihosting libraries have additional hooks to enable a project to send debugging information to an IDE

running on a PC. The nohosting libraries have this additional capability removed. The none versions of the

toolchains have no standard I/O capability (i.e., no printf()).

For some example projects (like si32HAL 1.0.1 sim3u1xx_Blinky), the compile-time library can be modified by

opening the myLinkerOptions_p32.ld file in the project directory and changing the uncommented line.

Figure 3. Using the myLinkerOptions_p32.ld File to Select the Project Library

The four lines in the file correspond to a library:

GROUP(libgcc.a libc.a libm.a libcr_newlib_nohost.a) (line 4): newlib nohosting

GROUP(libgca.a libc.a libm.a libcr_newlib_semihost.a) (line 5): newlib semihosting

GROUP(libcr_semihost.a libcr_c.a libcr_eabihelpers.a) (line 6): redlib semihosting

GROUP(libcr_nohost.a libcr_c.a libcr_eabihelpers.a) (line 7): redlib nohosting

The none libraries do not have corresponding entries in this file. Add these lines to add support for none:

GROUP(libgcc.a libc.a libm.a): newlib none

GROUP(libcr_c.a libcr_eabihelpers.a): redlib none

After setting the myLinkerOptions_P32.ld file to the correct setting, set the IDE to the same library using these

steps:

1. Left-click on the project_name in the Project Explorer view.

2. Select Properties.

3. Click on C/C++ BuildSettingsTool Settings tabMCU LinkerTarget and select the desired

library from the Use C library drop-down menu. Figure 4 shows this dialog in the Precision32 IDE.

4. Clean and Build the project.

AppBuilder projects do not have a myLinkerOptions_P32.ld file and can use the Quickstart view setting only.

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