[Bug target/53842] New: avr second write to volatile register gets dropped
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53842
Bug #: 53842
Summary: avr second write to volatile register gets dropped
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: j...@jtan.com
Hi,
I'm seeing volatile writes get dropped with avr-gcc 4.7.0 (as packaged in
Debian). This didn't happen with 4.5.3. Example:
$ cat test.c
#define SPDR (*(volatile char *)(0x2e + 0x20))
#define SPSR (*(volatile char *)(0x2d + 0x20))
static inline char transfer(char tx) {
SPDR = tx;
while (!(SPSR & 0x80)) continue;
return SPDR;
}
void foo(void) {
transfer(0xff);
//asm("":::"memory");
transfer(0xff);
}
$ avr-gcc -c -mmcu=at90usb1287 -O1 test.c -o test.o
$ avr-objdump avr-objdump -d test.o
test.o: file format elf32-avr
Disassembly of section .text:
:
0: 8f ef ldi r24, 0xFF ; 255
2: 8e bd out 0x2e, r24 ; 46
4: 0d b4 in r0, 0x2d; 45
6: 07 fe sbrsr0, 7
8: 00 c0 rjmp.+0 ; 0xa
a: 8e b5 in r24, 0x2e ; 46
c: 0d b4 in r0, 0x2d; 45
e: 07 fe sbrsr0, 7
10: 00 c0 rjmp.+0 ; 0x12
12: 8e b5 in r24, 0x2e ; 46
14: 08 95 ret
Note only one "out" there. If I compile that same code on 4.5.3, or uncomment
that memory barrier and compile on 4.7.0, I get the correct code:
0: 8f ef ldi r24, 0xFF ; 255
2: 8e bd out 0x2e, r24 ; 46
4: 0d b4 in r0, 0x2d; 45
6: 07 fe sbrsr0, 7
8: 00 c0 rjmp.+0 ; 0xa
a: 8e b5 in r24, 0x2e ; 46
c: 8f ef ldi r24, 0xFF ; 255
e: 8e bd out 0x2e, r24 ; 46
10: 0d b4 in r0, 0x2d; 45
12: 07 fe sbrsr0, 7
14: 00 c0 rjmp.+0 ; 0x16
16: 8e b5 in r24, 0x2e ; 46
18: 08 95 ret
-
This seems similar to pr53085, but that bug was listed as existing on 4.5 as
well, while this one seems to be a regression.
[Bug target/53842] avr second write to volatile register gets dropped
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53842 jim at jtan dot com changed: What|Removed |Added Status|WAITING |RESOLVED Known to work||4.7.1 Resolution||FIXED Known to fail||4.7.0 --- Comment #2 from jim at jtan dot com 2012-07-04 15:08:03 UTC --- You're right, 4.7.1 looks fine. Thanks.
[Bug debug/75194] -flto loses .debug_macro section
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=75194 --- Comment #5 from jim at jtan dot com --- Thank you!
[Bug lto/75194] New: -flto loses .debug_macro section
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=75194
Bug ID: 75194
Summary: -flto loses .debug_macro section
Product: gcc
Version: 5.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: jim at jtan dot com
Target Milestone: ---
With -flto, I can't get "info macros" to work in GDB. The .debug_macros
section seems to be lost:
$ cat test.c
#define HELLO "hello"
int main() {}
$ gcc -Wall -Wextra -o test1 test.c -ggdb3
$ gcc -Wall -Wextra -o test2 test.c -ggdb3 -flto
$ readelf -WS test1 > 1
$ readelf -WS test2 > 2
$ diff -u 1 2
--- 1 2016-08-12 15:10:04.153446089 -0400
+++ 2 2016-08-12 15:10:07.393523823 -0400
@@ -1,4 +1,4 @@
-There are 37 section headers, starting at offset 0x3398:
+There are 36 section headers, starting at offset 0x1460:
Section Headers:
[Nr] Name TypeAddress OffSize ES Flg
Lk Inf Al
@@ -31,14 +31,13 @@
[26] .bss NOBITS 00600890 000890 08 00 WA
0 0 1
[27] .comment PROGBITS 000890 25 01 MS
0 0 1
[28] .debug_arangesPROGBITS 0008b5 30 00
0 0 1
- [29] .debug_info PROGBITS 0008e5 56 00
0 0 1
- [30] .debug_abbrev PROGBITS 00093b 3a 00
0 0 1
- [31] .debug_line PROGBITS 000975 57 00
0 0 1
- [32] .debug_strPROGBITS 0009cc 0019b8 01 MS
0 0 1
- [33] .debug_macro PROGBITS 002384 0005f2 00
0 0 1
- [34] .shstrtab STRTAB 003239 000159 00
0 0 1
- [35] .symtab SYMTAB 002978 0006c0 18
36 53 8
- [36] .strtab STRTAB 003038 000201 00
0 0 1
+ [29] .debug_info PROGBITS 0008e5 52 00
0 0 1
+ [30] .debug_abbrev PROGBITS 000937 37 00
0 0 1
+ [31] .debug_line PROGBITS 00096e 39 00
0 0 1
+ [32] .debug_strPROGBITS 0009a7 e0 01 MS
0 0 1
+ [33] .shstrtab STRTAB 001312 00014c 00
0 0 1
+ [34] .symtab SYMTAB 000a88 000690 18
35 51 8
+ [35] .strtab STRTAB 001118 0001fa 00
0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
[Bug lto/75194] -flto loses .debug_macro section
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=75194 jim at jtan dot com changed: What|Removed |Added Version|5.4.0 |6.1.1 --- Comment #2 from jim at jtan dot com --- Same result with GCC 6.1.1.
