diff --git a/lib/Target/AArch64/AArch64RegisterInfo.cpp b/lib/Target/AArch64/AArch64RegisterInfo.cpp
index d2d5205cf2d..1aef31baad2 100644
--- a/lib/Target/AArch64/AArch64RegisterInfo.cpp
+++ b/lib/Target/AArch64/AArch64RegisterInfo.cpp
@@ -100,7 +100,7 @@ AArch64RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
     Reserved.set(AArch64::W29);
   }
 
-  if (TT.isOSDarwin() || MF.getSubtarget<AArch64Subtarget>().isX18Reserved()) {
+  if (MF.getSubtarget<AArch64Subtarget>().isX18Reserved()) {
     Reserved.set(AArch64::X18); // Platform register
     Reserved.set(AArch64::W18);
   }
@@ -127,8 +127,7 @@ bool AArch64RegisterInfo::isReservedReg(const MachineFunction &MF,
     return true;
   case AArch64::X18:
   case AArch64::W18:
-    return TT.isOSDarwin() ||
-           MF.getSubtarget<AArch64Subtarget>().isX18Reserved();
+    return MF.getSubtarget<AArch64Subtarget>().isX18Reserved();
   case AArch64::FP:
   case AArch64::W29:
     return TFI->hasFP(MF) || TT.isOSDarwin();
@@ -398,12 +397,11 @@ unsigned AArch64RegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC,
   case AArch64::GPR64RegClassID:
   case AArch64::GPR32commonRegClassID:
   case AArch64::GPR64commonRegClassID:
-    return 32 - 1                                // XZR/SP
-      - (TFI->hasFP(MF) || TT.isOSDarwin()) // FP
-      - (TT.isOSDarwin() ||
-         MF.getSubtarget<AArch64Subtarget>()
-             .isX18Reserved()) // X18 reserved as platform register
-      - hasBasePointer(MF);    // X19
+    return 32 - 1                                   // XZR/SP
+              - (TFI->hasFP(MF) || TT.isOSDarwin()) // FP
+              - MF.getSubtarget<AArch64Subtarget>()
+                    .isX18Reserved() // X18 reserved as platform register
+              - hasBasePointer(MF);  // X19
   case AArch64::FPR8RegClassID:
   case AArch64::FPR16RegClassID:
   case AArch64::FPR32RegClassID:
diff --git a/test/CodeGen/AArch64/arm64-platform-reg.ll b/test/CodeGen/AArch64/arm64-platform-reg.ll
index 13381e8560d..f3af01a7355 100644
--- a/test/CodeGen/AArch64/arm64-platform-reg.ll
+++ b/test/CodeGen/AArch64/arm64-platform-reg.ll
@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=arm64-apple-ios -o - %s | FileCheck %s --check-prefix=CHECK-RESERVE-X18
+; RUN: llc -mtriple=arm64-apple-ios -mattr=+reserve-x18 -o - %s | FileCheck %s --check-prefix=CHECK-RESERVE-X18
 ; RUN: llc -mtriple=arm64-freebsd-gnu -mattr=+reserve-x18 -o - %s | FileCheck %s --check-prefix=CHECK-RESERVE-X18
 ; RUN: llc -mtriple=arm64-linux-gnu -o - %s | FileCheck %s
 
diff --git a/test/CodeGen/AArch64/arm64-stackmap.ll b/test/CodeGen/AArch64/arm64-stackmap.ll
index 1a4df7a6f2d..3eb1d275300 100644
--- a/test/CodeGen/AArch64/arm64-stackmap.ll
+++ b/test/CodeGen/AArch64/arm64-stackmap.ll
@@ -1,5 +1,5 @@
-; RUN: llc -mtriple=arm64-apple-darwin                             < %s | FileCheck %s
-; RUN: llc -mtriple=arm64-apple-darwin -fast-isel -fast-isel-abort=1 < %s | FileCheck %s
+; RUN: llc -mtriple=arm64-apple-darwin -mattr=+reserve-x18                             < %s | FileCheck %s
+; RUN: llc -mtriple=arm64-apple-darwin -mattr=+reserve-x18 -fast-isel -fast-isel-abort=1 < %s | FileCheck %s
 ;
 ; Note: Print verbose stackmaps using -debug-only=stackmaps.