[LLD] Remove assert from Relocations.h

[zturner]

Summary

This is triggering the following warning:

In file included from D:\src\llvm\tools\lld\ELF\Relocations.cpp:44:
D:\src\llvm\tools\lld\ELF/Relocations.h(101,28):  error: comparison of constant 64 with expression of type 'lld::elf::RelExpr' is always true [-Werror,-Wtautological-constant-out-of-range-compare]
  assert(0 <= Expr && Expr < 64 && "RelExpr is too large for 64-bit mask!");
                      ~~~~ ^ ~~
C:\Program Files (x86)\Windows Kits\10\include\10.0.14393.0\ucrt\assert.h(33,17):  note: expanded from macro 'assert'
            (!!(expression)) ||                                                              \
                ^~~~~~~~~~

which kills my -Werror build. Since ubsan should catch cases of values larger than 64 being passed in, it seems like the assert might not be strictly necessary. Either way, we need some way to get rid of this warning.

[ruiu]

What does -Wtautological-constant-out-of-range-compare do? This assert is to prevent future programmers error, so it is always true, and that's not wrong. Sean added this assert, and I don't think we want to get rid of it.

[joerg]

Depending on sanitizers to enforce constraints is bogus. They don't work everywhere. *sigh* Guess we have to cast it to int explicitly.

[ruiu]

LGTM

lld/trunk/ELF/Relocations.h

struct RelExprMaskBuilder<Head, Tail...> {
   }
 };
 
 // Return true if `Expr` is one of `Exprs`.
 // There are fewer than 64 RelExpr's, so we can represent any set of
 // RelExpr's as a constant bit mask and test for membership with a
 // couple cheap bitwise operations.
 template <RelExpr... Exprs> bool isRelExprOneOf(RelExpr Expr) {
-  assert(0 <= Expr && Expr < 64 && "RelExpr is too large for 64-bit mask!");
+  assert(0 <= Expr && (int)Expr < 64 && "RelExpr is too large for 64-bit mask!");
   return (uint64_t(1) << Expr) & RelExprMaskBuilder<Exprs...>::build();
 }
 
 // Architecture-neutral representation of relocation.
 struct Relocation {
   RelExpr Expr;
   uint32_t Type;
   uint64_t Offset;