Fix regression after D150436

[XinWang10]

Summary

llvm-clang-x86_64-expensive-checks-debian will fail after D150436 merged.
The fail occurred in X86, I changed the sort rule in AsmMatcher in Patch D150436, so x86 code will arrive line 633 first(will not affect other targets).
The logic here want to use the order record written in source file to make AsmMatcher to first use AVX instructions, it used field HasPositionOrder.
But the condition here just makes sure one of the compared record is subclass of Instruction and has field HasPositionOrder true, and didn't check another.

[skan]

LGTM

[RKSimon]

Confirmed this fixes my broken EXPENSIVE_CHECKS builds

[aaron.ballman]

We should land this sooner rather than later, llvm-tblgen currently crashes on stock debug builds with MSVC because of their checked iterators (so this doesn't require an expensive checks build to reproduce) -- we *really* need a post-commit CI bot with that functionality enabled.

llvm/utils/TableGen/AsmMatcherEmitter.cpp

bool operator<(const MatchableInfo &RHS) const {
     }
 
     // For X86 AVX/AVX512 instructions, we prefer vex encoding because the
     // vex encoding size is smaller. Since X86InstrSSE.td is included ahead
     // of X86InstrAVX512.td, the AVX instruction ID is less than AVX512 ID.
     // We use the ID to sort AVX instruction before AVX512 instruction in
     // matching table.
     if (TheDef->isSubClassOf("Instruction") &&
-        TheDef->getValueAsBit("HasPositionOrder"))
+        TheDef->getValueAsBit("HasPositionOrder") &&
+        RHS.TheDef->isSubClassOf("Instruction") &&
+        RHS.TheDef->getValueAsBit("HasPositionOrder"))
       return TheDef->getID() < RHS.TheDef->getID();
 
     // Give matches that require more features higher precedence. This is useful
     // because we cannot define AssemblerPredicates with the negation of
     // processor features. For example, ARM v6 "nop" may be either a HINT or
     // MOV. With v6, we want to match HINT. The assembler has no way to
     // predicate MOV under "NoV6", but HINT will always match first because it
     // requires V6 while MOV does not.