Make LocationSize a proper Optional type; NFC

This is the second in a series of changes intended to make
https://reviews.llvm.org/D44748 more easily reviewable. Please see that
patch for more context. The first change being r344012.

Since I was requested to do all of this with post-commit review, this is
about as small as I can make this patch.

This patch makes LocationSize into an actual type that wraps a uint64_t;
users are required to call getValue() in order to get the size now. If
the LocationSize has an Unknown size (e.g. if LocSize ==
MemoryLocation::UnknownSize), getValue() will assert.

This also adds DenseMap specializations for LocationInfo, which required
taking two more values from the set of values LocationInfo can
represent. Hence, heavy users of multi-exabyte arrays or structs may
observe slightly lower-quality code as a result of this change.

The intent is for getValue()s to be very close to a corresponding
hasValue() (which is often spelled `!= MemoryLocation::UnknownSize`).
Sadly, small diff context appears to crop that out sometimes, and the
last change in DSE does require a bit of nonlocal reasoning about
control-flow. :/

This also removes an assert, since it's now redundant with the assert in
getValue().

llvm-svn: 344013

1 files changed, 6 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index 0a3a00b8380..810c2fee0e0 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -354,8 +354,8 @@ static OverwriteResult isOverwrite(const MemoryLocation &Later,
       Earlier.Size == MemoryLocation::UnknownSize)
     return OW_Unknown;
 
-  const uint64_t LaterSize = Later.Size;
-  const uint64_t EarlierSize = Earlier.Size;
+  const uint64_t LaterSize = Later.Size.getValue();
+  const uint64_t EarlierSize = Earlier.Size.getValue();
 
   const Value *P1 = Earlier.Ptr->stripPointerCasts();
   const Value *P2 = Later.Ptr->stripPointerCasts();
@@ -1004,11 +1004,10 @@ static bool removePartiallyOverlappedStores(AliasAnalysis *AA,
     Instruction *EarlierWrite = OI.first;
     MemoryLocation Loc = getLocForWrite(EarlierWrite);
     assert(isRemovable(EarlierWrite) && "Expect only removable instruction");
-    assert(Loc.Size != MemoryLocation::UnknownSize && "Unexpected mem loc");
 
     const Value *Ptr = Loc.Ptr->stripPointerCasts();
     int64_t EarlierStart = 0;
-    int64_t EarlierSize = int64_t(Loc.Size);
+    int64_t EarlierSize = int64_t(Loc.Size.getValue());
     GetPointerBaseWithConstantOffset(Ptr, EarlierStart, DL);
     OverlapIntervalsTy &IntervalMap = OI.second;
     Changed |=
@@ -1205,8 +1204,9 @@ static bool eliminateDeadStores(BasicBlock &BB, AliasAnalysis *AA,
           assert(!EnablePartialOverwriteTracking && "Do not expect to perform "
                                                     "when partial-overwrite "
                                                     "tracking is enabled");
-          int64_t EarlierSize = DepLoc.Size;
-          int64_t LaterSize = Loc.Size;
+          // The overwrite result is known, so these must be known, too.
+          int64_t EarlierSize = DepLoc.Size.getValue();
+          int64_t LaterSize = Loc.Size.getValue();
           bool IsOverwriteEnd = (OR == OW_End);
           MadeChange |= tryToShorten(DepWrite, DepWriteOffset, EarlierSize,
                                     InstWriteOffset, LaterSize, IsOverwriteEnd);