Compiling and running the same test case with gcc-4.2.3 and gcc-4.3.0 shows that in the latter case performance takes an almost 3x hit:
" [EMAIL PROTECTED]:/mnt/sda1/sergei/learning_octave> /maxtor5/sergei/AppsFromScratchWD/install/gcc-4.2.3/binsh/gcc -Wall -mtune=native -march=native -O2 -msse -lm complex_multiplication_testcase.c -o complex_multiplication_testcase [EMAIL PROTECTED]:/mnt/sda1/sergei/learning_octave> time ./complex_multiplication_testcase executions of straightforward_multiply_with_ptrs() took 6.77 seconds at line number 136 of 'complex_multiplication_testcase.c' file executions of straightforward_multiply() took 6.74 seconds at line number 154 of 'complex_multiplication_testcase.c' file executions of straightforward_multiply_2_signals() took 8.62 seconds at line number 172 of 'complex_multiplication_testcase.c' file real 0m22.326s user 0m22.121s sys 0m0.012s [EMAIL PROTECTED]:/mnt/sda1/sergei/learning_octave> /maxtor5/sergei/AppsFromScratchWD/install/gcc-4.3.0/binsh/gcc -Wall -mtune=native -march=native -O2 -msse -lm complex_multiplication_testcase.c -o complex_multiplication_testcase [EMAIL PROTECTED]:/mnt/sda1/sergei/learning_octave> time ./complex_multiplication_testcase executions of straightforward_multiply_with_ptrs() took 18.17 seconds at line number 136 of 'complex_multiplication_testcase.c' file executions of straightforward_multiply() took 16.91 seconds at line number 154 of 'complex_multiplication_testcase.c' file executions of straightforward_multiply_2_signals() took 30.64 seconds at line number 172 of 'complex_multiplication_testcase.c' file real 1m6.306s user 1m5.676s sys 0m0.056s [EMAIL PROTECTED]:/mnt/sda1/sergei/learning_octave> " - see, for example, executions of straightforward_multiply() took 6.74 seconds vs executions of straightforward_multiply() took 16.91 seconds and user 0m22.121s vs user 1m5.676s . FWIW, gcc-3.4.6 shows comparable to gcc-4.2.3 results, albeit slightly worse, so it looks like the issue is very much gcc-4.3.0 specific. I'll upload the test case. -- Summary: severe perfromance degradation with "float complex" type Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: major Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: sergstesh at yahoo dot com GCC build triplet: i686-pc-linux-gnu GCC host triplet: i686-pc-linux-gnu GCC target triplet: i686-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35709