[avr-libc-commit] [2543] Document differences in register usage for AVR_TINY architecture.

[j]

Revision: 2543
          http://svn.sv.gnu.org/viewvc/?view=rev&root=avr-libc&revision=2543
Author:   joerg_wunsch
Date:     2017-06-16 16:59:33 -0400 (Fri, 16 Jun 2017)
Log Message:
-----------
Document differences in register usage for AVR_TINY architecture.

Modified Paths:
--------------
    trunk/avr-libc/ChangeLog
    trunk/avr-libc/doc/api/faq.dox

Modified: trunk/avr-libc/ChangeLog
===================================================================
--- trunk/avr-libc/ChangeLog    2017-06-12 22:08:58 UTC (rev 2542)
+++ trunk/avr-libc/ChangeLog    2017-06-16 20:59:33 UTC (rev 2543)
@@ -1,3 +1,8 @@
+2017-06-16  Joerg Wunsch <address@hidden>
+
+       * doc/api/faq.dox (faq_reg_usage): Document differences for
+       AVR_TINY architecture.
+
 2017-06-11  Joerg Wunsch <address@hidden>
 
        Submitted by Georg-Johann Lay:

Modified: trunk/avr-libc/doc/api/faq.dox
===================================================================
--- trunk/avr-libc/doc/api/faq.dox      2017-06-12 22:08:58 UTC (rev 2542)
+++ trunk/avr-libc/doc/api/faq.dox      2017-06-16 20:59:33 UTC (rev 2543)
@@ -674,6 +674,9 @@
 Calling C subroutines can clobber any of them -
 the caller is responsible for saving and restoring.
 
+\note For the AVR_TINY architecture (ATtiny10 and relatives),
+r18 and r19 are call-saved.
+
 - <strong>Call-saved registers (r2-r17, r28-r29):</strong><br>
 May be allocated by gcc for local data.
 Calling C subroutines leaves them unchanged.
@@ -686,6 +689,9 @@
 situations where the compiler assigns them for
 argument passing.
 
+\note For the AVR_TINY architecture (ATtiny10 and relatives),
+r18 and r19 are call-saved, and r0 through r16 do not exist.
+
 - <strong>Fixed registers (r0, r1):</strong><br>
 Never allocated by gcc for local data, but often
 used for fixed purposes:
@@ -706,6 +712,9 @@
 and restore r1 on exit (in case it was non-zero).
 </p>
 
+\note For the AVR_TINY architecture (ATtiny10 and relatives),
+r16 is used as temporary register, and r17 as zero.
+
 - <strong>Function call conventions:</strong><br>
 Arguments - allocated left to right, r25 to r8.
 All arguments are aligned to start in even-numbered