addressed review comments.

Author: Mikhail Gudim

llvm/include/llvm/CodeGen/Register.h

@@ -49,9 +49,9 @@ class Register {
 
   /// Convert a non-negative frame index to a stack slot register value.
   static Register index2StackSlot(int FI) {
-    unsigned FIMasked = FI & Register::StackSlotMask;
-    assert(isUInt<MaxFrameIndexBitwidth>(FIMasked) &&
+    assert(isInt<MaxFrameIndexBitwidth>(FI) &&
            "Frame index must be at most 30 bit as an unsigned integer");
+    unsigned FIMasked = FI & Register::StackSlotMask;
     return Register(FIMasked | Register::StackSlotZero);
   }
 

llvm/unittests/CodeGen/RegisterTest.cpp

@@ -13,21 +13,21 @@ using namespace llvm;
 
 namespace {
 TEST(RegisterTest, Idx2StackSlot) {
-  ASSERT_EQ(Register::index2StackSlot(0), Register::StackSlotZero);
-  ASSERT_EQ(Register::index2StackSlot(-1),
-            Register::StackSlotZero | Register::StackSlotMask);
-  ASSERT_EQ(Register::index2StackSlot(Register::StackSlotMask),
-            Register::StackSlotZero | Register::StackSlotMask);
-  ASSERT_EQ(Register::index2StackSlot(1), Register::StackSlotZero | 1);
+  EXPECT_EQ(Register::index2StackSlot(0), Register::StackSlotZero);
+  EXPECT_EQ(Register::index2StackSlot(1), Register::StackSlotZero | 1);
+  EXPECT_EQ(Register::index2StackSlot(-1), Register::StackSlotZero | Register::StackSlotMask);
+  // check that we do not crash on the highest possible value of frame index.
+  EXPECT_NO_FATAL_FAILURE(Register::index2StackSlot((1 << 29) - 1));
+  // check that we do not crash on the lowest possible value of frame index.
+  EXPECT_NO_FATAL_FAILURE(Register::index2StackSlot(-(1 << 29)));
 }
 
 TEST(RegisterTest, StackSlotIndex) {
-  Register Reg;
   std::vector<int64_t> FIs = {0, 1 - 1, (1 << 29) - 1, -(1 << 29)};
 
   for (int64_t FI : FIs) {
-    Reg = Register::index2StackSlot(FI);
-    ASSERT_EQ(Reg.stackSlotIndex(), FI);
+    Register Reg = Register::index2StackSlot(FI);
+    EXPECT_EQ(Reg.stackSlotIndex(), FI);
   }
 }
 } // end namespace