Verifier: Fix assertion on range metadata with equal bounds

[arsenm]

Summary

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

[nikic]

LGTM

[arsenm]

a2ce822a096517e36fbc6ac9404b0b5ef5e6a2bc

llvm/lib/IR/Verifier.cpp

ConstantInt *High =
         mdconst::dyn_extract<ConstantInt>(Range->getOperand(2 * i + 1));
     Check(High, "The upper limit must be an integer!", High);
     Check(High->getType() == Low->getType() &&
           High->getType() == Ty->getScalarType(),
           "Range types must match instruction type!", &I);
 
     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);
     if (i != 0) {
       Check(CurRange.intersectWith(LastRange).isEmptySet(),
             "Intervals are overlapping", Range);
       Check(LowV.sgt(LastRange.getLower()), "Intervals are not in order",
             Range);

llvm/test/Assembler/range.ll

+; 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

 ; CHECK: It should have at least one range!
 
 define <2 x i8> @vector_range_wrong_type(ptr %x) {
   %y = load <2 x i8>, ptr %x, !range !19
   ret <2 x i8> %y
 }
 !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}