llvm/lib/Transforms
Duncan P. N. Exon Smith 698c0a7097 ValueMapper: Treat LocalAsMetadata more like function-local Values
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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265759 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-08 00:33:44 +00:00
..
Hello Remove autoconf support 2016-01-26 21:29:08 +00:00
InstCombine [InstCombine] Don't sink an instr after a catchswitch 2016-04-01 17:28:17 +00:00
Instrumentation Make helper functions static. NFC. 2016-04-07 10:10:09 +00:00
IPO NFC: make AtomicOrdering an enum class 2016-04-06 21:19:33 +00:00
ObjCARC ADT: Remove == and != comparisons between ilist iterators and pointers 2016-02-21 20:39:50 +00:00
Scalar [GVN] Address review comments for D18662 2016-04-07 15:55:11 +00:00
Utils ValueMapper: Treat LocalAsMetadata more like function-local Values 2016-04-08 00:33:44 +00:00
Vectorize Revert r265535 until we know how we can fix the bots 2016-04-06 14:06:32 +00:00
CMakeLists.txt
LLVMBuild.txt