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[Bug c/29932] New: avr-gcc wrongly optimizes bit sets/resets for IO register 0x20
- From: "mlitwack at employees dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 21 Nov 2006 17:28:36 -0000
- Subject: [Bug c/29932] New: avr-gcc wrongly optimizes bit sets/resets for IO register 0x20
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
avr-gcc tries to optimize bit sets and resets to IO register 0x20 (PCMSK1 in
the ATtiny24) into sbi/cbi instructions. However, sbi/cbi are not suitable for
registers >= 0x20.
IO registers 0x1f and 0x21 are handled correctly, so it appears to be just
register address 0x20.
Here is an example that will fail (filtered out from avr-libc):
------------------
typedef unsigned char uint8_t;
#define _MMIO_BYTE(mem_addr) (*(volatile uint8_t *)(mem_addr))
#define _SFR_IO8(io_addr) _MMIO_BYTE((io_addr) + 0x20)
#define PCMSK1 _SFR_IO8(0x20)
main()
{
PCMSK1 |= 0x01;
}
------------------
$ avr-gcc -Os fail.c
/tmp/ccJwjyqk.s: Assembler messages:
/tmp/ccJwjyqk.s:19: Error: number must be less than 32
No optimization will work fine as will other values for PCMSK1.
Using gcc snapshot from 20061014.
-mark
--
Summary: avr-gcc wrongly optimizes bit sets/resets for IO
register 0x20
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: mlitwack at employees dot org
GCC build triplet: i586-linux-gnu
GCC host triplet: i586-linux-gnu
GCC target triplet: avr-unknown-none
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29932