ARM: Add a postRA pass to legalize stack offsets. Greedy approach (reserve IP).

src/IceInstARM32.def

 //===- subzero/src/IceInstARM32.def - X-Macros for ARM32 insts --*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines properties of ARM32 instructions in the form of x-macros.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SUBZERO_SRC_ICEINSTARM32_DEF
 #define SUBZERO_SRC_ICEINSTARM32_DEF
 
 // NOTE: PC and SP are not considered isInt, to avoid register allocating.
 //
 // For the NaCl sandbox we also need to r9 for TLS, so just reserve always.
 // TODO(jvoung): Allow r9 to be isInt when sandboxing is turned off
 // (native mode).
 //
+// IP is not considered isInt to reserve it as a scratch register. A scratch
+// register is useful for expanding instructions post-register allocation.
+//
 // LR is not considered isInt to avoid being allocated as a register.
 // It is technically preserved, but save/restore is handled separately,
 // based on whether or not the function MaybeLeafFunc.
 #define REGARM32_GPR_TABLE                                                     \
   /* val, encode, name, scratch, preserved, stackptr, frameptr, isInt, isFP */ \
   X(Reg_r0,  = 0,            "r0",  1, 0, 0, 0, 1, 0)                   \
   X(Reg_r1,  = Reg_r0 + 1,   "r1",  1, 0, 0, 0, 1, 0)                   \
   X(Reg_r2,  = Reg_r0 + 2,   "r2",  1, 0, 0, 0, 1, 0)                   \
   X(Reg_r3,  = Reg_r0 + 3,   "r3",  1, 0, 0, 0, 1, 0)                   \
   X(Reg_r4,  = Reg_r0 + 4,   "r4",  0, 1, 0, 0, 1, 0)                   \
   X(Reg_r5,  = Reg_r0 + 5,   "r5",  0, 1, 0, 0, 1, 0)                   \
   X(Reg_r6,  = Reg_r0 + 6,   "r6",  0, 1, 0, 0, 1, 0)                   \
   X(Reg_r7,  = Reg_r0 + 7,   "r7",  0, 1, 0, 0, 1, 0)                   \
   X(Reg_r8,  = Reg_r0 + 8,   "r8",  0, 1, 0, 0, 1, 0)                   \
   X(Reg_r9,  = Reg_r0 + 9,   "r9",  0, 1, 0, 0, 0, 0)                   \
   X(Reg_r10, = Reg_r0 + 10,  "r10", 0, 1, 0, 0, 1, 0)                   \
   X(Reg_fp,  = Reg_r0 + 11,  "fp",  0, 1, 0, 1, 1, 0)                   \
-  X(Reg_ip,  = Reg_r0 + 12,  "ip",  1, 0, 0, 0, 1, 0)                   \
+  X(Reg_ip,  = Reg_r0 + 12,  "ip",  1, 0, 0, 0, 0, 0)                   \
   X(Reg_sp,  = Reg_r0 + 13,  "sp",  0, 0, 1, 0, 0, 0)                   \
   X(Reg_lr,  = Reg_r0 + 14,  "lr",  0, 0, 0, 0, 0, 0)                   \
   X(Reg_pc,  = Reg_r0 + 15,  "pc",  0, 0, 0, 0, 0, 0)                   \
 //#define X(val, encode, name, scratch, preserved, stackptr, frameptr,
 //          isInt, isFP)
 
 // TODO(jvoung): List FP registers and know S0 == D0 == Q0, etc.
 // Be able to grab even registers, and the corresponding odd register
 // for each even register.
 
@@ skipping 62 matching lines @@
   X(LS, 9, HI, "ls") /* unsigned lower or same */                       \
   X(GE, 10, LT, "ge") /* signed greater than or equal */                \
   X(LT, 11, GE, "lt") /* signed less than */                            \
   X(GT, 12, LE, "gt") /* signed greater than */                         \
   X(LE, 13, GT, "le") /* signed less than or equal */                   \
   X(AL, 14, kNone, "") /* always (unconditional) */                     \
   X(kNone, 15, kNone, "??") /* special condition / none */              \
 //#define(tag, encode, opp, emit)
 
 #endif // SUBZERO_SRC_ICEINSTARM32_DEF