Adds the loop end location to the loop metadata.

This additional information can be used to improve the locations when generating remarks for loops.

Patch by Florian Hahn.

Differential Revision: https://reviews.llvm.org/D25763



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286227 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/LoopInfo.h

@@ -367,6 +367,27 @@ extern template class LoopBase<BasicBlock, Loop>;
 /// in the CFG are neccessarily loops.
 class Loop : public LoopBase<BasicBlock, Loop> {
 public:
+  /// \brief A range representing the start and end location of a loop.
+  class LocRange {
+    DebugLoc Start;
+    DebugLoc End;
+
+  public:
+    LocRange() {}
+    LocRange(DebugLoc Start) : Start(std::move(Start)), End(std::move(Start)) {}
+    LocRange(DebugLoc Start, DebugLoc End) : Start(std::move(Start)),
+                                             End(std::move(End)) {}
+
+    const DebugLoc &getStart() const { return Start; }
+    const DebugLoc &getEnd() const { return End; }
+
+    /// \brief Check for null.
+    ///
+    explicit operator bool() const {
+      return Start && End;
+    }
+  };
+
   Loop() {}
 
   /// Return true if the specified value is loop invariant.
@@ -474,6 +495,9 @@ public:
   /// it returns an unknown location.
   DebugLoc getStartLoc() const;
 
+  /// Return the source code span of the loop.
+  LocRange getLocRange() const;
+
   StringRef getName() const {
     if (BasicBlock *Header = getHeader())
       if (Header->hasName())

lib/Analysis/LoopInfo.cpp

@@ -305,23 +305,40 @@ bool Loop::isAnnotatedParallel() const {
 }
 
 DebugLoc Loop::getStartLoc() const {
+  return getLocRange().getStart();
+}
+
+Loop::LocRange Loop::getLocRange() const {
   // If we have a debug location in the loop ID, then use it.
-  if (MDNode *LoopID = getLoopID())
-    for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i)
-      if (DILocation *L = dyn_cast<DILocation>(LoopID->getOperand(i)))
-        return DebugLoc(L);
+  if (MDNode *LoopID = getLoopID()) {
+    DebugLoc Start;
+    // We use the first DebugLoc in the header as the start location of the loop
+    // and if there is a second DebugLoc in the header we use it as end location
+    // of the loop.
+    for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
+      if (DILocation *L = dyn_cast<DILocation>(LoopID->getOperand(i))) {
+        if (!Start)
+          Start = DebugLoc(L);
+        else
+          return LocRange(Start, DebugLoc(L));
+      }
+    }
+
+    if (Start)
+      return LocRange(Start);
+  }
 
   // Try the pre-header first.
   if (BasicBlock *PHeadBB = getLoopPreheader())
     if (DebugLoc DL = PHeadBB->getTerminator()->getDebugLoc())
-      return DL;
+      return LocRange(DL);
 
   // If we have no pre-header or there are no instructions with debug
   // info in it, try the header.
   if (BasicBlock *HeadBB = getHeader())
-    return HeadBB->getTerminator()->getDebugLoc();
+    return LocRange(HeadBB->getTerminator()->getDebugLoc());
 
-  return DebugLoc();
+  return LocRange();
 }
 
 bool Loop::hasDedicatedExits() const {