[ARM] Fix issue with large xor constants.

[dmgreen]

Summary

Fixup to rL325573 for large xor constants.

Thanks to Eli Friedman for the catch.

[efriedma]

LGTM

llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp

if (ST->isThumb2() && NegImm < 1<<12)
       // icmp X, #-C -> cmn X, #C
       return 0;
     if (ST->isThumb() && NegImm < 1<<8)
       // icmp X, #-C -> adds X, #C
       return 0;
   }
 
   // xor a, -1 can always be folded to MVN
-  if (Opcode == Instruction::Xor) {
-    int64_t NegImm = Imm.getSExtValue();
-    if (NegImm == -1)
-      return 0;
-  }
+  if (Opcode == Instruction::Xor && Imm.isAllOnesValue())
 
   return getIntImmCost(Imm, Ty);
 }
 
 int ARMTTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst, Type *Src,
                                  const Instruction *I) {
   int ISD = TLI->InstructionOpcodeToISD(Opcode);
   assert(ISD && "Invalid opcode");

llvm/trunk/test/CodeGen/Thumb/mvn.ll

for.body:
   %inc = add nuw nsw i32 %i, 1
   %exitcond = icmp eq i32 %inc, 10
   br i1 %exitcond, label %for.cond.cleanup, label %for.body
 
 for.cond.cleanup:
   ret void
 }
 
+
+define void @test128(i128* %a) {
+; CHECK-LABEL: test128:
+; CHECK:         ldr r1, [r0, #4]
+; CHECK-NEXT:    ldr r2, .LCPI8_0
+; CHECK-NEXT:    eors r2, r1
+; CHECK-NEXT:    str r2, [r0, #4]
+; CHECK-NEXT:    ldr r1, [r0]
+; CHECK-NEXT:    ldr r2, .LCPI8_1
+; CHECK-NEXT:    eors r2, r1
+; CHECK-NEXT:    str r2, [r0]
+; CHECK-NEXT:    ldr r1, [r0, #8]
+; CHECK-NEXT:    ldr r2, .LCPI8_2
+; CHECK-NEXT:    eors r2, r1
+; CHECK-NEXT:    str r2, [r0, #8]
+; CHECK-NEXT:    bx lr
+; CHECK-NEXT:    .p2align 2
+; CHECK-NEXT:  .LCPI8_0:
+; CHECK-NEXT:    .long 4075008415
+; CHECK-NEXT:  .LCPI8_1:
+; CHECK-NEXT:    .long 2080661269
+; CHECK-NEXT:  .LCPI8_2:
+; CHECK-NEXT:    .long 6692605
+  %x = load i128, i128* %a
+  %xn = xor i128 %x, 123456789123456789123456789
+  store i128 %xn, i128* %a
+  ret void
+}
+