llvm-project/llvm/include
Duncan P. N. Exon Smith 4ec55f8ab6 Reapply "ValueMapper: Treat LocalAsMetadata more like function-local Values"
This reverts commit r265765, reapplying r265759 after changing a call from
LocalAsMetadata::get to ValueAsMetadata::get (and adding a unit test).  When a
local value is mapped to a constant (like "i32 %a" => "i32 7"), the new debug
intrinsic operand may no longer be pointing at a local.

    http://lab.llvm.org:8080/green/job/clang-stage1-configure-RA_build/19020/

The previous coommit message follows:

--

This is a partial re-commit -- maybe more of a re-implementation -- of
r265631 (reverted in r265637).

This makes RF_IgnoreMissingLocals behave (almost) consistently between
the Value and the Metadata hierarchy.  In particular:

  - MapValue returns nullptr or "metadata !{}" for missing locals in
    MetadataAsValue/LocalAsMetadata bridging paris, depending on
    the RF_IgnoreMissingLocals flag.

  - MapValue doesn't memoize LocalAsMetadata-related results.

  - MapMetadata no longer deals with LocalAsMetadata or
    RF_IgnoreMissingLocals at all.  (This wasn't in r265631 at all, but
    I realized during testing it would make the patch simpler with no
    loss of generality.)

r265631 went too far, making both functions universally ignore
RF_IgnoreMissingLocals.  This broke building (e.g.) compiler-rt.
Reassociate (and possibly other passes) don't currently maintain
dominates-use invariants for metadata operands, resulting in IR like
this:

    define void @foo(i32 %arg) {
      call void @llvm.some.intrinsic(metadata i32 %x)
      %x = add i32 1, i32 %arg
    }

If the inliner chooses to inline @foo into another function, then
RemapInstruction will call `MapValue(metadata i32 %x)` and assert that
the return is not nullptr.

I've filed PR27273 to add a Verifier check and fix the underlying
problem in the optimization passes.

As a workaround, return `!{}` instead of nullptr for unmapped
LocalAsMetadata when RF_IgnoreMissingLocals is unset.  Otherwise, match
the behaviour of r265631.

Original commit message:

    ValueMapper: Make LocalAsMetadata match function-local Values

    Start treating LocalAsMetadata similarly to function-local members of
    the Value hierarchy in MapValue and MapMetadata.

      - Don't memoize them.
      - Return nullptr if they are missing.

    This also cleans up ConstantAsMetadata to stop listening to the
    RF_IgnoreMissingLocals flag.

llvm-svn: 265768
2016-04-08 03:13:22 +00:00
..
llvm Reapply "ValueMapper: Treat LocalAsMetadata more like function-local Values" 2016-04-08 03:13:22 +00:00
llvm-c [GCC] Attribute ifunc support in llvm 2016-04-07 12:32:19 +00:00