llvm dev - Sep 2016 - Q about PlaceSafepoints pass

Hello list,

I'm experimenting with proof of concept statepoint GC for LLVM and
currently trying to follow some guidelines of
http://llvm.org/docs/Statepoints.html

Namely applying PlaceSafepoints should introduce statepoint intrinsics at
the right spots in the IR. Following the given example
http://llvm.org/docs/Statepoints.html#placesafepoints I did:

dmitryolsh$ cat sp.ll

declare void @foo()

define void @test() gc "statepoint-example" {

  call void @foo()

  ret void

}

declare void @do_safepoint()

define void @gc.safepoint_poll() {

  call void @do_safepoint()

  ret void

}

#Applying the place-safepoints:

dmitryolsh$ opt -place-safepoints -S  sp.ll

; ModuleID = 'sp.ll'

source_filename = "sp.ll"


declare void @foo()


define void @test() gc "statepoint-example" {

  call void @do_safepoint()

  call void @foo()

  ret void

}

declare void @do_safepoint()

define void @gc.safepoint_poll() {

  call void @do_safepoint()

  ret void

}

This is compared to the expected output with intrinsics:

define void @test() gc "statepoint-example" {

  %safepoint_token = call token (i64, i32, void ()*, i32, i32, ...)*
@llvm.experimental.gc.statepoint.p0f_isVoidf(i64 2882400000, i32 0, void
()* @do_safepoint, i32 0, i32 0, i32 0, i32 0)

  %safepoint_token1 = call token (i64, i32, void ()*, i32, i32, ...)*
@llvm.experimental.gc.statepoint.p0f_isVoidf(i64 2882400000, i32 0, void
()* @foo, i32 0, i32 0, i32 0, i32 0)

  ret void

}


So it doesn't quite work as advertised. Am I missing something obvious or
is it a bug in docs/pass ?


---

Dmitry Olshansky
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