[llvm] Negative frame indicies as register. (PR #164459)

[Craig Topper via llvm-commits]

================
@@ -35,7 +36,10 @@ class Register {
   // DenseMapInfo<unsigned> uses -1u and -2u.
   static_assert(std::numeric_limits<decltype(Reg)>::max() >= 0xFFFFFFFF,
                 "Reg isn't large enough to hold full range.");
-  static constexpr unsigned FirstStackSlot = 1u << 30;
+  static constexpr unsigned MaxFrameIndexBitwidth = 30;
+  static constexpr unsigned FirstStackSlot = 1u << MaxFrameIndexBitwidth;
+  static const unsigned StackSlotMask =
----------------
topperc wrote:

Can this be constexpr too?

https://github.com/llvm/llvm-project/pull/164459