[LoopUtils] Extend findStringMetadataForLoop to return the value for metadata

E.g. for:

  !1 = {"llvm.distribute", i32 1}

it now returns the MDOperand for 1.

I will use this in LoopDistribution to check the value of the metadata.

Note that the change is backward-compatible with its current use in
LoopVersioningLICM.  An Optional implicitly converts to a bool depending
whether it contains a value or not.

llvm-svn: 267190

1 files changed, 7 insertions, 3 deletions

diff --git a/llvm/include/llvm/Transforms/Utils/LoopUtils.h b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
index cb789b80a93..ff0d673d16e 100644
--- a/llvm/include/llvm/Transforms/Utils/LoopUtils.h
+++ b/llvm/include/llvm/Transforms/Utils/LoopUtils.h
@@ -385,9 +385,13 @@ void computeLICMSafetyInfo(LICMSafetyInfo *, Loop *);
 /// \brief Returns the instructions that use values defined in the loop.
 SmallVector<Instruction *, 8> findDefsUsedOutsideOfLoop(Loop *L);
 
-/// \brief Find string metadata for loop, if it exists return true, else return
-/// false.
-bool findStringMetadataForLoop(Loop *TheLoop, StringRef Name);
+/// \brief Find string metadata for loop
+///
+/// If it has a value (e.g. {"llvm.distribute", 1} return the value as an
+/// operand or null otherwise.  If the string metadata is not found return
+/// Optional's not-a-value.
+Optional<const MDOperand *> findStringMetadataForLoop(Loop *TheLoop,
+                                                      StringRef Name);
 
 /// \brief Set input string into loop metadata by keeping other values intact.
 void addStringMetadataToLoop(Loop *TheLoop, const char *MDString,