Extract out getConstantRangeFromMetadata; NFC

The loop idiom creating a ConstantRange is repeated twice in the
codebase, time to give it a name and a home.

The loop is also repeated in `rangeMetadataExcludesValue`, but using
`getConstantRangeFromMetadata` there would not be an NFC -- the range
returned by `getConstantRangeFromMetadata` may contain a value that none
of the subranges did.

llvm-svn: 251180

1 files changed, 22 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index ea2321e8..0fe8717 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4041,3 +4041,25 @@ SelectPatternResult llvm::matchSelectPattern(Value *V,
   return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS, TrueVal, FalseVal,
                               LHS, RHS);
 }
+
+ConstantRange llvm::getConstantRangeFromMetadata(MDNode &Ranges) {
+  const unsigned NumRanges = Ranges.getNumOperands() / 2;
+  assert(NumRanges >= 1 && "Must have at least one range!");
+  assert(Ranges.getNumOperands() % 2 == 0 && "Must be a sequence of pairs");
+
+  auto *FirstLow = mdconst::extract<ConstantInt>(Ranges.getOperand(0));
+  auto *FirstHigh = mdconst::extract<ConstantInt>(Ranges.getOperand(1));
+
+  ConstantRange CR(FirstLow->getValue(), FirstHigh->getValue());
+
+  for (unsigned i = 1; i < NumRanges; ++i) {
+    auto *Low = mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 0));
+    auto *High = mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 1));
+
+    // Note: unionWith will potentially create a range that contains values not
+    // contained in any of the original N ranges.
+    CR = CR.unionWith(ConstantRange(Low->getValue(), High->getValue()));
+  }
+
+  return CR;
+}