[Bug tree-optimization/79390] [7 Regression] 10% performance drop in SciMark2 LU after r242550

[vincenzo.innocente at cern dot ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79390

--- Comment #19 from vincenzo Innocente <vincenzo.innocente at cern dot ch> ---
Could you please have a look also to c++ and lto: this is what I get on my
skylake:
for c++ or lto -fno-split-paths pessimizes
[innocent@vinavx3 scimark2TMP]$ gcc -march=native -Wall -Ofast *.c -lm ;
./a.out | grep LU
LU              Mflops:  5920.14    (M=100, N=100)
[innocent@vinavx3 scimark2TMP]$ gcc -march=native -Wall -Ofast *.c -lm
-fno-split-paths ; ./a.out | grep LU
LU              Mflops:  6136.33    (M=100, N=100)
[innocent@vinavx3 scimark2TMP]$ gcc -march=native -Wall -Ofast *.c -lm -flto ;
./a.out | grep LU
LU              Mflops:  5809.93    (M=100, N=100)
[innocent@vinavx3 scimark2TMP]$ gcc -march=native -Wall -Ofast *.c -lm -flto
-fno-split-paths ; ./a.out | grep LU
LU              Mflops:  5630.24    (M=100, N=100)
[innocent@vinavx3 scimark2TMP]$ c++ -march=native -Wall -Ofast *.c -lm ;
./a.out | grep LU
LU              Mflops:  6001.47    (M=100, N=100)
[innocent@vinavx3 scimark2TMP]$ c++ -march=native -Wall -Ofast *.c -lm
-fno-split-paths ; ./a.out | grep LU
LU              Mflops:  5920.14    (M=100, N=100)
[innocent@vinavx3 scimark2TMP]$ c++ -march=native -Wall -Ofast *.c -lm -flto;
./a.out | grep LU
LU              Mflops:  5434.16    (M=100, N=100)
[innocent@vinavx3 scimark2TMP]$ c++ -march=native -Wall -Ofast *.c -lm -flto
-fno-split-paths ; ./a.out | grep LU
LU              Mflops:  5434.16    (M=100, N=100)