Require intervals in the range metadata to be in a canonical form: They must

be non contiguous, non overlapping and sorted by the lower end.

While this is technically a backward incompatibility, every frontent currently
produces range metadata with a single interval and we don't have any pass
that merges intervals yet, so no existing bitcode files should be rejected by
this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157741 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LangRef.html

@@ -3054,6 +3054,8 @@ call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
    <li>The range should not represent the full or empty set. That is,
        <tt>a!=b</tt>. </li>
 </ul>
+<p> In addiion, the pairs must be in signed order of the lower bound and
+  they must be non contigous.</p>
 
 <p>Examples:</p>
 <div class="doc_code">
@@ -3061,10 +3063,12 @@ call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
   %a = load i8* %x, align 1, !range !0 ; Can only be 0 or 1
   %b = load i8* %y, align 1, !range !1 ; Can only be 255 (-1), 0 or 1
   %c = load i8* %z, align 1, !range !2 ; Can only be 0, 1, 3, 4 or 5
+  %d = load i8* %z, align 1, !range !3 ; Can only be -2, -1, 3, 4 or 5
 ...
 !0 = metadata !{ i8 0, i8 2 }
 !1 = metadata !{ i8 255, i8 2 }
 !2 = metadata !{ i8 0, i8 2, i8 3, i8 6 }
+!3 = metadata !{ i8 -2, i8 0, i8 3, i8 6 }
 </pre>
 </div>
 </div>

lib/VMCore/Verifier.cpp

@@ -1383,6 +1383,8 @@ void Verifier::visitLoadInst(LoadInst &LI) {
     Assert1(NumOperands % 2 == 0, "Unfinished range!", Range);
     unsigned NumRanges = NumOperands / 2;
     Assert1(NumRanges >= 1, "It should have at least one range!", Range);
+
+    APInt LastHigh;
     for (unsigned i = 0; i < NumRanges; ++i) {
       ConstantInt *Low = dyn_cast<ConstantInt>(Range->getOperand(2*i));
       Assert1(Low, "The lower limit must be an integer!", Low);
@@ -1391,8 +1393,20 @@ void Verifier::visitLoadInst(LoadInst &LI) {
       Assert1(High->getType() == Low->getType() &&
               High->getType() == ElTy, "Range types must match load type!",
               &LI);
-      Assert1(High->getValue() != Low->getValue(), "Range must not be empty!",
-              Range);
+
+      APInt HighV = High->getValue();
+      APInt LowV = Low->getValue();
+      Assert1(HighV != LowV, "Range must not be empty!", Range);
+      if (i != 0) {
+        Assert1(Low->getValue().sgt(LastHigh),
+                "Intervals are overlapping, contiguous or not in order", Range);
+        if (i == NumRanges - 1 && HighV.slt(LowV)) {
+          APInt First = dyn_cast<ConstantInt>(Range->getOperand(0))->getValue();
+          Assert1(First.sgt(HighV),
+                  "First and last intervals are contiguous or overlap", Range);
+        }
+      }
+      LastHigh = High->getValue();
     }
   }
 

test/Verifier/range-1.ll

@@ -76,3 +76,43 @@ entry:
 }
 !8 = metadata !{i8 0, i8 0}
 ; CHECK: Range must not be empty!
+
+define i8 @f10(i8* %x) {
+entry:
+  %y = load i8* %x, align 1, !range !9
+  ret i8 %y
+}
+!9 = metadata !{i8 0, i8 2, i8 1, i8 3}
+; CHECK: Intervals are overlapping, contiguous or not in order
+
+define i8 @f11(i8* %x) {
+entry:
+  %y = load i8* %x, align 1, !range !10
+  ret i8 %y
+}
+!10 = metadata !{i8 0, i8 2, i8 2, i8 3}
+; CHECK: Intervals are overlapping, contiguous or not in order
+
+define i8 @f12(i8* %x) {
+entry:
+  %y = load i8* %x, align 1, !range !11
+  ret i8 %y
+}
+!11 = metadata !{i8 1, i8 2, i8 -1, i8 0}
+; CHECK: Intervals are overlapping, contiguous or not in order
+
+define i8 @f13(i8* %x) {
+entry:
+  %y = load i8* %x, align 1, !range !12
+  ret i8 %y
+}
+!12 = metadata !{i8 1, i8 3, i8 5, i8 1}
+; CHECK: First and last intervals are contiguous or overlap
+
+define i8 @f14(i8* %x) {
+entry:
+  %y = load i8* %x, align 1, !range !13
+  ret i8 %y
+}
+!13 = metadata !{i8 1, i8 3, i8 5, i8 2}
+; CHECK: First and last intervals are contiguous or overlap

test/Verifier/range-2.ll

@@ -20,3 +20,17 @@ entry:
   ret i8 %y
 }
 !2 = metadata !{i8 1, i8 3, i8 5, i8 42}
+
+define i8 @f4(i8* %x) {
+entry:
+  %y = load i8* %x, align 1, !range !3
+  ret i8 %y
+}
+!3 = metadata !{i8 -1, i8 0, i8 1, i8 2}
+
+define i8 @f5(i8* %x) {
+entry:
+  %y = load i8* %x, align 1, !range !4
+  ret i8 %y
+}
+!4 = metadata !{i8 -1, i8 0, i8 1, i8 -2}