Verifier: Fix assertion on range metadata with equal bounds

This only worked if the same values were the min or max. We also seem
to be missing proper assembler tests for this.

Author: arsenm

llvm/lib/IR/Verifier.cpp

@@ -3927,6 +3927,12 @@ void Verifier::visitRangeMetadata(Instruction &I, MDNode *Range, Type *Ty) {
 
     APInt HighV = High->getValue();
     APInt LowV = Low->getValue();
+
+    // ConstantRange asserts if the ranges are the same except for the min/max
+    // value. Leave the cases it tolerates for the empty range error below.
+    Check(LowV != HighV || LowV.isMaxValue() || LowV.isMinValue(),
+          "The upper and lower limits cannot be the same value", &I);
+
     ConstantRange CurRange(LowV, HighV);
     Check(!CurRange.isEmptySet() && !CurRange.isFullSet(),
           "Range must not be empty!", Range);

llvm/test/Assembler/range.ll

@@ -0,0 +1,31 @@
+; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+
+define i8 @neg1_zero(ptr %x) {
+; CHECK-LABEL: define i8 @neg1_zero
+; CHECK-SAME: (ptr [[X:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[Y:%.*]] = load i8, ptr [[X]], align 1, !range [[RNG0:![0-9]+]]
+; CHECK-NEXT:    ret i8 [[Y]]
+;
+entry:
+  %y = load i8, ptr %x, align 1, !range !0
+  ret i8 %y
+}
+
+define <2 x i8> @neg1_zero_vector(ptr %x) {
+; CHECK-LABEL: define <2 x i8> @neg1_zero_vector
+; CHECK-SAME: (ptr [[X:%.*]]) {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[Y:%.*]] = load <2 x i8>, ptr [[X]], align 1, !range [[RNG0]]
+; CHECK-NEXT:    ret <2 x i8> [[Y]]
+;
+entry:
+  %y = load <2 x i8>, ptr %x, align 1, !range !0
+  ret <2 x i8> %y
+}
+
+!0 = !{i8 -1, i8 0}
+
+;.
+; CHECK: [[RNG0]] = !{i8 -1, i8 0}
+;.

llvm/test/Verifier/range-1.ll

@@ -154,3 +154,10 @@ define <2 x i8> @vector_range_wrong_type(ptr %x) {
 }
 !19 = !{i16 0, i16 10}
 ; CHECK: Range types must match instruction type!
+
+define i32 @range_assert(ptr %x) {
+  %y = load i32, ptr %x, !range !20
+  ret i32 %y
+}
+; CHECK: The upper and lower limits cannot be the same value{{$}}
+!20 = !{i32 123, i32 123}