Hi
I am trying to run a C/C++ project for the PowerPC with GCC 4.2.2 with
optimization O1 enabled. While it runs perfectly without, it fails if
-O1 is enabled.
Trying to isolate the harmful optimization, i tried to specify all
flags which are enabled with O1, one by one.
My invocations look now like this:
/usr/local/powerpc-eabi/bin/powerpc-eabi-gcc -c test.c -o testNO1.o
-fdefer-pop -fomit-frame-pointer -fguess-branch-probability
-fcprop-registers -fif-conversion -fif-conversion2 -fipa-pure-const
-fipa-reference -ftree-ccp -ftree-dce -ftree-dominator-opts
-ftree-dse -ftree-ter -ftree-lrs -ftree-sra -ftree-copyrename
-ftree-fre -ftree-copy-prop -ftree-sink -ftree-salias -funit-at-a-time
-ftree-ch
/usr/local/powerpc-eabi/bin/powerpc-eabi-gcc -c test.c -o testO1.o -O1
In addition to the options listed in the manual as options used by -O1
I also included -ftree-sink -ftree-salias, which are mentioned in the
manual but not in the list, and -fipa-pure-const -fipa-reference,
which are not documented but apparently set (see
http://gcc.gnu.org/viewcvs/tags/gcc_4_2_2_release/gcc/opts.c?view=markup - as
there is no "unrecognized command line" error i guess i specified them
correctly).
But still the output files differ.
Does anyone know which optimizations may be used additionally and
whether i can toggle them manually?
Regards.
Peter
The test.c looks like this:
extern void bar(int x);
foo(int x)
{
bar(x);
}
The resultings disassemblies are:
testNO1.o: file format elf32-powerpc
Disassembly of section .text:
00000000 <foo>:
0: 94 21 ff f0 stwu r1,-16(r1)
4: 7c 08 02 a6 mflr r0
8: 90 01 00 14 stw r0,20(r1)
c: 90 61 00 08 stw r3,8(r1)
10: 80 61 00 08 lwz r3,8(r1)
14: 48 00 00 01 bl 14 <foo+0x14>
18: 80 01 00 14 lwz r0,20(r1)
1c: 7c 08 03 a6 mtlr r0
20: 38 21 00 10 addi r1,r1,16
24: 4e 80 00 20 blr
testO1.o: file format elf32-powerpc
Disassembly of section .text:
00000000 <foo>:
0: 94 21 ff f8 stwu r1,-8(r1)
4: 7c 08 02 a6 mflr r0
8: 90 01 00 0c stw r0,12(r1)
c: 48 00 00 01 bl c <foo+0xc>
10: 80 01 00 0c lwz r0,12(r1)
14: 7c 08 03 a6 mtlr r0
18: 38 21 00 08 addi r1,r1,8
1c: 4e 80 00 20 blr
