Index: llvm/trunk/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp
@@ -1502,6 +1502,23 @@
   return false;
 }
 
+/// Does the 'Range' metadata (which must be a valid MD_range operand list)
+/// ensure that the value it's attached to is never Value?  'RangeType' is
+/// is the type of the value described by the range.
+static bool rangeMetadataExcludesValue(MDNode* Ranges,
+                                       const APInt& Value) {
+  const unsigned NumRanges = Ranges->getNumOperands() / 2;
+  assert(NumRanges >= 1);
+  for (unsigned i = 0; i < NumRanges; ++i) {
+    ConstantInt *Lower = cast<ConstantInt>(Ranges->getOperand(2*i + 0));
+    ConstantInt *Upper = cast<ConstantInt>(Ranges->getOperand(2*i + 1));
+    ConstantRange Range(Lower->getValue(), Upper->getValue());
+    if (Range.contains(Value))
+      return false;
+  }
+  return true;
+}
+
 /// isKnownNonZero - Return true if the given value is known to be non-zero
 /// when defined.  For vectors return true if every element is known to be
 /// non-zero when defined.  Supports values with integer or pointer type and
@@ -1518,6 +1535,18 @@
     return false;
   }
 
+  if (Instruction* I = dyn_cast<Instruction>(V)) {
+    if (MDNode *Ranges = I->getMetadata(LLVMContext::MD_range)) {
+      // If the possible ranges don't contain zero, then the value is
+      // definitely non-zero.
+      if (IntegerType* Ty = dyn_cast<IntegerType>(V->getType())) {
+        const APInt ZeroValue(Ty->getBitWidth(), 0);
+        if (rangeMetadataExcludesValue(Ranges, ZeroValue))
+          return true;
+      }
+    }
+  }
+
   // The remaining tests are all recursive, so bail out if we hit the limit.
   if (Depth++ >= MaxDepth)
     return false;
Index: llvm/trunk/test/Transforms/InstCombine/icmp-range.ll
===================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp-range.ll
+++ llvm/trunk/test/Transforms/InstCombine/icmp-range.ll
@@ -0,0 +1,61 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+; These should be InstSimplify checks, but most of the code
+; is currently only in InstCombine.  TODO: move supporting code
+
+; Definitely out of range
+define i1 @test_nonzero(i32* nocapture readonly %arg) {
+; CHECK-LABEL:test_nonzero
+; CHECK: ret i1 true
+  %val = load i32* %arg, !range !0
+  %rval = icmp ne i32 %val, 0
+  ret i1 %rval
+}
+define i1 @test_nonzero2(i32* nocapture readonly %arg) {
+; CHECK-LABEL:test_nonzero2
+; CHECK: ret i1 false
+  %val = load i32* %arg, !range !0
+  %rval = icmp eq i32 %val, 0
+  ret i1 %rval
+}
+
+; Potentially in range
+define i1 @test_nonzero3(i32* nocapture readonly %arg) {
+; CHECK-LABEL: test_nonzero3
+; Check that this does not trigger - it wouldn't be legal
+; CHECK: icmp
+  %val = load i32* %arg, !range !1
+  %rval = icmp ne i32 %val, 0
+  ret i1 %rval
+}
+
+; Definitely in range
+define i1 @test_nonzero4(i8* nocapture readonly %arg) {
+; CHECK-LABEL: test_nonzero4
+; CHECK: ret i1 false
+  %val = load i8* %arg, !range !2
+  %rval = icmp ne i8 %val, 0
+  ret i1 %rval
+}
+
+define i1 @test_nonzero5(i8* nocapture readonly %arg) {
+; CHECK-LABEL: test_nonzero5
+; CHECK: ret i1 false
+  %val = load i8* %arg, !range !2
+  %rval = icmp ugt i8 %val, 0
+  ret i1 %rval
+}
+
+; Cheaper checks (most values in range meet requirements)
+define i1 @test_nonzero6(i8* %argw) {
+; CHECK-LABEL: test_nonzero6
+; CHECK: icmp ne i8 %val, 0
+  %val = load i8* %argw, !range !3
+  %rval = icmp sgt i8 %val, 0
+  ret i1 %rval
+}
+
+
+!0 = metadata !{i32 1, i32 6} 
+!1 = metadata !{i32 0, i32 6} 
+!2 = metadata !{i8 0, i8 1} 
+!3 = metadata !{i8 0, i8 6}