Fix LIR stack slot formatting and parsing

Summary:
Claude came up with this, but it doesn't impact anything, but it says it's right.

Fix the PhyLocation::toString() output format for stack slots and the
corresponding LIR parser to use a consistent sign convention.

Stack slot locations are stored as negative offsets from the frame pointer.
Previously toString() printed them as raw negative values inside parens
(e.g. "[RBP(-8)]") which didn't match the parser's regex for stack slots.

Change toString() to print "[RBP - 8]" format (negating the stored value)
and fix the parser to negate token.data when setting stack slots, so the
round-trip through print/parse is consistent.

Reviewed By: alexmalyshev

Differential Revision: D98161190

fbshipit-source-id: 83bd3ff43e211a3b0f4109da2c41c7302433e0a7

Author: DinoV

cinderx/Jit/lir/parser.cpp

@@ -46,7 +46,7 @@ Parser::Token Parser::getNextToken(const char* str) {
       {"[RD][0-9]+", kPhyReg},
 #endif
       {"XMM[0-9]+", kPhyReg},
-      {R"(\[RBP[ ]?-[ ]?(\d+)\])", kStack},
+      {R"(\[RBP\((-?\d+)\)\])", kStack},
       {"\\[(0x[0-9a-fA-F]+)\\]", kAddress},
       {R"((\d+)(\(0x[0-9a-fA-F]+\))?)", kImmediate},
       {"BB%(\\d+)", kBasicBlockRef},