[llvm-bugs] [Bug 36670] New: [llvm-mca][x86] Teach how to identify pairs of adjacent operations that can be macro fused.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36670

            Bug ID: 36670
           Summary: [llvm-mca][x86] Teach how to identify pairs of
                    adjacent operations that can be macro fused.
           Product: new-bugs
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: andrea.dibiagio at gmail.com
                CC: llvm-bugs at lists.llvm.org

On modern x86 processors, a 'cmp/test' followed by a conditional jump can be
micro fused. The advantage is that the fused pair only consumes a single slot
in the dispatch group.

The tool should be extended to address macro-fusion. Ideally, LLVM should
expose this information (possibly through the MC subtarget interface; this is
just an idea...).

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