[llvm-bugs] [Bug 43247] New: Long live ranges of constants don't get rematerialized

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=43247

            Bug ID: 43247
           Summary: Long live ranges of constants don't get rematerialized
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Register Allocator
          Assignee: unassignedbugs at nondot.org
          Reporter: aemerson at apple.com
                CC: llvm-bugs at lists.llvm.org, quentin.colombet at gmail.com

We're enabling the localizer pass for optimizations in AArch64 GlobalISel,
which is a pass that tries to duplicate and move defs of constant-like
instructions close to their uses, so as to reduce the live ranges and register
pressure.

It would be good if the greedy register allocator could handle this problem for
us, but it seems to have been written with only SelectionDAG in mind which is
always block-local and doesn't have any notion of live range in its graph
representation.

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