[llvm-bugs] [Bug 44115] New: Benchmark partialsums - worse perf with -march=haswell

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=44115

            Bug ID: 44115
           Summary: Benchmark partialsums - worse perf with -march=haswell
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: david.bolvansky at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

Benchmark source:
https://github.com/llvm/llvm-test-suite/blob/master/SingleSource/Benchmarks/BenchmarkGame/partialsums.c

clang cc.c -Ofast -lm 
0m0,133s


clang cc.c -Ofast -march=haswell -lm 
0m0,146s

Codegen: https://godbolt.org/z/sZpeCQ


clang cc.c -Ofast -fno-unroll-loops -lm
0m0,129s


So, there is codegen and loop unrolling issue here..

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