[ARM] Correct range in isLegalAddressImm

[dmgreen]

Summary

The ranges in isLegalAddressImm were off by one, not allowing the maximum values for unscaled offsets.

[samtebbs]

Nice

llvm/lib/Target/ARM/ARMBaseInstrInfo.h

 // Given a memory access Opcode, check that the give Imm would be a valid Offset
 // for this instruction using its addressing mode.
 inline bool isLegalAddressImm(unsigned Opcode, int Imm,
                               const TargetInstrInfo *TII) {
   const MCInstrDesc &Desc = TII->get(Opcode);
   unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
   switch (AddrMode) {
   case ARMII::AddrModeT2_i7:
-    return std::abs(Imm) < (((1 << 7) * 1) - 1);
+    return std::abs(Imm) < ((1 << 7) * 1);
   case ARMII::AddrModeT2_i7s2:
-    return std::abs(Imm) < (((1 << 7) * 2) - 1) && Imm % 2 == 0;
+    return std::abs(Imm) < ((1 << 7) * 2) && Imm % 2 == 0;
   case ARMII::AddrModeT2_i7s4:
-    return std::abs(Imm) < (((1 << 7) * 4) - 1) && Imm % 4 == 0;
+    return std::abs(Imm) < ((1 << 7) * 4) && Imm % 4 == 0;
   case ARMII::AddrModeT2_i8:
-    return std::abs(Imm) < (((1 << 8) * 1) - 1);
-  case ARMII::AddrMode2:
-    return std::abs(Imm) < (((1 << 12) * 1) - 1);
-  case ARMII::AddrModeT2_i12:
-    return Imm >= 0 && Imm < (((1 << 12) * 1) - 1);
+    return std::abs(Imm) < ((1 << 8) * 1);
   case ARMII::AddrModeT2_i8s4:
-    return std::abs(Imm) < (((1 << 8) * 4) - 1) && Imm % 4 == 0;
+    return std::abs(Imm) < ((1 << 8) * 4) && Imm % 4 == 0;
+  case ARMII::AddrModeT2_i12:
+    return Imm >= 0 && Imm < ((1 << 12) * 1);
+  case ARMII::AddrMode2:
+    return std::abs(Imm) < ((1 << 12) * 1);
   default:
     llvm_unreachable("Unhandled Addressing mode");
   }
 }
 
 // Return true if the given intrinsic is a gather
 inline bool isGather(IntrinsicInst *IntInst) {
   if (IntInst == nullptr)

llvm/test/CodeGen/Thumb2/store-prepostinc.mir

liveins:
   - { reg: '$r1', virtual-reg: '' }
 body:             |
   bb.0 (%ir-block.0):
     liveins: $r0, $r1
 
     ; CHECK-LABEL: name: STR_post255
     ; CHECK: liveins: $r0, $r1
     ; CHECK-NEXT: {{  $}}
-    ; CHECK-NEXT: t2STRi12 killed renamable $r1, renamable $r0, 0, 14 /* CC::al */, $noreg :: (store (s32))
-    ; CHECK-NEXT: renamable $r0 = nuw t2ADDri killed renamable $r0, 255, 14 /* CC::al */, $noreg, $noreg
+    ; CHECK-NEXT: early-clobber $r0 = t2STR_POST killed $r1, $r0, 255, 14 /* CC::al */, $noreg :: (store (s32))
     ; CHECK-NEXT: tBX_RET 14 /* CC::al */, $noreg, implicit $r0
     t2STRi12 killed renamable $r1, renamable $r0, 0, 14 /* CC::al */, $noreg :: (store (s32))
     renamable $r0 = nuw t2ADDri killed renamable $r0, 255, 14 /* CC::al */, $noreg, $noreg
     tBX_RET 14 /* CC::al */, $noreg, implicit $r0
 
 ...
 ---
 name:            STR_post256