ARM compiler options: what changed

Revision 0 to 1. Removed lines have a minus sign; added lines have a plus sign.

Title: ARM compiler options

New		Line
1	+	## Overview
2	+
3	+	The FPC compiler lets you create (cross)compilers for various [[ARM]] instruction sets, floating point units etc.
4	+
5	+	Current (FPC 2.6.x/2.7.x) compilers (and RTL PPUs etc) are built for just one ABI and cannot output other ABIs once built - e.g. adding `-dFPC_ARMHF` when compiling a program will not change anything: <http://lists.freepascal.org/lists/fpc-devel/2013-May/032093.html>
6	+
7	+	The options below are passed in OPTS= when building FPC. When building a cross compiler, some of them can/should be passed in CROSSOPT as well.
8	+
9	+	## ABI
10	+
11	+	ABIs are selected using the -Ca switch.
12	+
13	+	> Note: Normally, specifying an ABI is not needed. Source: <http://www.mail-archive.com/fpc-pascal@lists.freepascal.org/msg35496.html>
14	+
15	+	- default: ?
16	+	- eabi: ?
17	+	- EABI HF is selected using `-dFPC_ARMHF`; the `-Ca eabihf` option is present but is not necessary (but may not hurt). (Source: <http://www.mail-archive.com/fpc-pascal@lists.freepascal.org/msg35487.html>)
18	+
19	+	## Instruction sets
20	+
21	+	Instructions sets are selected using the `-Cp` switch. Possible instruction sets (note many sets are backward compatible):
22	+
23	+	- ARMV3
24	+	- ARMV4
25	+	- ARMV4T
26	+	- ARMV5
27	+	- ARMV5T
28	+	- ARMV5TEJ
29	+	- ARMV6: e.g. in Raspberry Pi; will probably work on most current hardware
30	+	- ARMV6K
31	+	- ARMV6T2
32	+	- ARMV6Z
33	+	- ARMV7: e.g. in Nokia N900, Nokia N9, Nokia N950
34	+	- ARMV7A: e.g. in Odroid U2, Odroid U3
35	+	- ARMV7R
36	+	- ARMV7M
37	+	- ARMV7EM
38	+
39	+	## Floating point support
40	+
41	+	Floating point support coprocessor (FPU) options are selected with the `-Cf` switch Possible FPU support options:
42	+
43	+	- soft: softfloat/no FPU support.
44	+	- vfpv2: e.g. on Raspberry Pi??
45	+	- vfpv3: e.g. on Odroid U2, Odroid U3
46	+	- vfpv3_d16
47	+
48	+	...
49	+
50	+	### Interactions
51	+
52	+	Below adapted from: [1](http://www.mail-archive.com/fpc-devel@lists.freepascal.org/msg28056.html)
53	+
54	+	- armel and armhf indicate how floating point (fp) values are passed.
55	+	- Armel means that all floating point values are always passed in integer registers.
56	+	- Armhf means that fp values are generally passed in floating point registers. As indicated above, armhf is settable by `-dFPC_ARMHF`; see above)
57	+
58	+	- The softfp/vfpv2 distinction for armel indicates how the fp operations are performed.
59	+	- Softfp means that all fp operations are performed by software
60	+	- vfpv2, vfpv3 means that fp operations are performed by the hardware. Although fp values are still passed in integer registers, they're copied to fp registers before performing the operation.
61	+
62	+	From an ABI point of view softfp and vfpv2 are compatible. However, vfpv2 executables will crash if run on a processor not having vfpv2 hardware.
63	+
64	+	## Other relevant options
65	+
66	+	- If you are using FPC 2.7.1+ and want to speed up floating point, you can also specify `-OoFASTMATH` to sacrifice precision for performance.
67	+
68	+	## See also
69	+
70	+	- [[Setup Cross Compile For ARM]]
71	+
72	+	---
73	+	From the Free Pascal wiki, page "ARM compiler options", as it stood on 2014-07-11 after a change by BigChimp, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).
74	+	Category: ARM
75	+	Category: FPC

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