[llvm-bugs] [Bug 27072] New: Spurious live variable in RewriteStatepointsForGC

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27072

            Bug ID: 27072
           Summary: Spurious live variable in RewriteStatepointsForGC
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: sanjoy at playingwithpointers.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

declare void @f(i32 addrspace(1)*)
declare i32 addrspace(1)* @get_ref() "gc-leaf-function"="true"

define void @g() gc "statepoint-example" {
entry:
  %ptr = call i32 addrspace(1)* @get_ref()
  call void @f(i32 addrspace(1)* %ptr)
  ret void
}

RS4GC think %ptr is live **over** the call to @f, which is too conservative.

 $ ./bin/opt -rewrite-statepoints-for-gc live.ll -S -spp-print-liveset
-disable-output
Live Variables:
 ptr   %ptr = call i32 addrspace(1)* @get_ref()

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