On 01/20/11 19:54, Roman Divacky wrote:
ok, I sat down and implemented what Hans Ottevanger told me to do :)
http://lev.vlakno.cz/~rdivacky/clang-gprof.patch
I have installed clang and the patch you provided in the following way:
cd /home/hans
mkdir clang
export PATH=/home/hans/clang/bin:$PATH
mkdir testllvm
cd testllvm
mkdir build
svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
cd llvm/tools
svn co http://llvm.org/svn/llvm-project/cfe/trunk clang
cd clang/
patch < /tmp/clang-gprof.patch 2>&1 | tee /tmp/log
cd ../../..
cd build
../llvm/configure --prefix=$HOME/clang
gmake -j 4
gmake install
This patch does three things:
1) emits "call .mcount" at the begining of every function body
The differences on i386 between profiled and non-profiled code are not
as obvious as with gcc (using diff on assembly output), but on first
inspection it looks correct.
2) changes the driver to link in gcrt1.o instead of crt1.o
3) changes all -lfoo to -lfoo_p except when the foo ends with _s in
the linker invocation
With gcc the libraries specified by the caller are left alone, maybe for
a good reason (more control over what really gets linked).
On amd64 (9.0-CURRENT r217444) calling
gcc -v -O2 -o tf tf.c -lm
yields
/usr/bin/ld --eh-frame-hdr -V -dynamic-linker /libexec/ld-elf.so.1 -o tf
/usr/lib/crt1.o /usr/lib/crti.o /usr/lib/crtbegin.o -L/usr/lib
-L/usr/lib /var/tmp//ccnOsNq4.o -lm -lgcc --as-needed -lgcc_s
--no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib/crtend.o /usr/lib/crtn.o
and
gcc -v -pg -O2 -o tf tf.c -lm
results in
/usr/bin/ld --eh-frame-hdr -V -dynamic-linker /libexec/ld-elf.so.1 -o tf
/usr/lib/gcrt1.o /usr/lib/crti.o /usr/lib/crtbegin.o -L/usr/lib
-L/usr/lib /var/tmp//cc9Btbiv.o -lm -lgcc_p -lgcc_eh_p -lc_p -lgcc_p
-lgcc_eh_p /usr/lib/crtend.o /usr/lib/crtn.o
Maybe it is wise to follow the gcc implementation here.
I am not sure that I did the right thing, especially in (3). Anyway,
the patch works for me (ie. produces a.out.gmon that seems to contain
meaningful data).
I would appreciate if you guys could test and review this. Letting me
know if this is correct.
On both my systems (i386 and amd64) something goes severely wrong when
linking several objects (all compiled with -pg, this is amd64):
clang -v -pg -O2 -Wall -o test test.o angle.o apsis.o error.o minmax.o
qags.o qext.o qk21.o sort.o timint.o zero.o vmol.o -lm
clang version 2.9 (trunk 123975)
Target: x86_64-unknown-freebsd9.0
Thread model: posix
"/usr/bin/ld" --eh-frame-hdr -dynamic-linker /libexec/ld-elf.so.1 -o
test /usr/lib/gcrt1.o /usr/lib/crti.o /usr/lib/crtbegin.o test.o angle.o
apsis.o error.o minmax.o qags.o qext.o qk21.o sort.o timint.o zero.o
vmol.o ld /usr/bin/ld --as-needed -lgcc_s --no-as-needed ld /usr/bin/ld
--as-needed -lgcc_s --no-as-needed /usr/lib/crtend.o /usr/lib/crtn.o
/usr/bin/ld: ld: No such file: No such file or directory
clang: error: linker command failed with exit code 1 (use -v to see
invocation)
Polishing the linker invocation a bit as follows
"/usr/bin/ld" --eh-frame-hdr -dynamic-linker /libexec/ld-elf.so.1 -o
test /usr/lib/gcrt1.o /usr/lib/crti.o /usr/lib/crtbegin.o test.o angle.o
apsis.o error.o minmax.o qags.o qext.o qk21.o sort.o timint.o zero.o
vmol.o -lm_p --as-needed -lgcc_s -lc_p --no-as-needed --as-needed
-lgcc_s --no-as-needed /usr/lib/crtend.o /usr/lib/crtn.o
yields a profiled executable. running gprof on the test.gmon file gives
results that are very similar to those when compiling with gcc: the
number of calls is identical and the time spent is comparable.
Perhaps the invocation of the linker still needs some work (or I must
redo my installation) but anyhow it looks like a good job. Thanks!
Kind regards,
Hans
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