[LoopUnroll] Use llvm.experimental.noalias.scope.decl for duplicating noalias metadata as needed

This is a fix for https://bugs.llvm.org/show_bug.cgi?id=39282. Compared to D90104, this version is based on part of the full restrict patched (D68484) and uses the `@llvm.experimental.noalias.scope.decl` intrinsic to track the location where !noalias and !alias.scope scopes have been introduced. This allows us to only duplicate the scopes that are really needed.

Notes:
- it also includes changes and tests from D90104

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D92887

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/LoopUnroll.cpp b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
index 6478143..ed1de9b 100644
--- a/llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -590,6 +590,11 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
                          << DIL->getFilename() << " Line: " << DIL->getLine());
           }
 
+  // Identify what noalias metadata is inside the loop: if it is inside the
+  // loop, the associated metadata must be cloned for each iteration.
+  SmallVector<MetadataAsValue *, 6> LoopLocalNoAliasDeclScopes;
+  identifyNoAliasScopesToClone(L->getBlocks(), LoopLocalNoAliasDeclScopes);
+
   for (unsigned It = 1; It != ULO.Count; ++It) {
     SmallVector<BasicBlock *, 8> NewBlocks;
     SmallDenseMap<const Loop *, Loop *, 4> NewLoops;
@@ -683,6 +688,15 @@ LoopUnrollResult llvm::UnrollLoop(Loop *L, UnrollLoopOptions ULO, LoopInfo *LI,
             AC->registerAssumption(II);
       }
     }
+
+    {
+      // Identify what other metadata depends on the cloned version. After
+      // cloning, replace the metadata with the corrected version for both
+      // memory instructions and noalias intrinsics.
+      std::string ext = (Twine("It") + Twine(It)).str();
+      cloneAndAdaptNoAliasScopes(LoopLocalNoAliasDeclScopes, NewBlocks,
+                                 Header->getContext(), ext);
+    }
   }
 
   // Loop over the PHI nodes in the original block, setting incoming values.