Index: lib/Target/AMDGPU/AMDGPU.td
===================================================================
--- lib/Target/AMDGPU/AMDGPU.td
+++ lib/Target/AMDGPU/AMDGPU.td
@@ -118,6 +118,11 @@
         "true",
         "Support flat address space">;
 
+def FeatureXNACK : SubtargetFeature<"xnack",
+        "EnableXNACK",
+        "true",
+        "Enable XNACK support">;
+
 def FeatureVGPRSpilling : SubtargetFeature<"vgpr-spilling",
         "EnableVGPRSpilling",
         "true",
Index: lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
+++ lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
@@ -417,13 +417,13 @@
     }
   }
 
-  if (VCCUsed || FlatUsed)
+  if (VCCUsed || FlatUsed || STM.isXNACKEnabled()) {
     MaxSGPR += 2;
 
-  if (FlatUsed) {
-    MaxSGPR += 2;
-    // 2 additional for VI+.
-    if (STM.getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS)
+    if (FlatUsed)
+      MaxSGPR += 2;
+
+    if (STM.isXNACKEnabled())
       MaxSGPR += 2;
   }
 
Index: lib/Target/AMDGPU/AMDGPUSubtarget.h
===================================================================
--- lib/Target/AMDGPU/AMDGPUSubtarget.h
+++ lib/Target/AMDGPU/AMDGPUSubtarget.h
@@ -76,6 +76,7 @@
   bool EnableIfCvt;
   bool EnableLoadStoreOpt;
   bool EnableUnsafeDSOffsetFolding;
+  bool EnableXNACK;
   unsigned WavefrontSize;
   bool CFALUBug;
   int LocalMemorySize;
@@ -290,6 +291,10 @@
   }
   bool isVGPRSpillingEnabled(const SIMachineFunctionInfo *MFI) const;
 
+  bool isXNACKEnabled() const {
+    return EnableXNACK;
+  }
+
   unsigned getMaxWavesPerCU() const {
     if (getGeneration() >= AMDGPUSubtarget::SOUTHERN_ISLANDS)
       return 10;
Index: lib/Target/AMDGPU/AMDGPUSubtarget.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUSubtarget.cpp
+++ lib/Target/AMDGPU/AMDGPUSubtarget.cpp
@@ -73,6 +73,7 @@
       CaymanISA(false), FlatAddressSpace(false), FlatForGlobal(false),
       EnableIRStructurizer(true), EnablePromoteAlloca(false), EnableIfCvt(true),
       EnableLoadStoreOpt(false), EnableUnsafeDSOffsetFolding(false),
+      EnableXNACK(false),
       WavefrontSize(0), CFALUBug(false), LocalMemorySize(0),
       EnableVGPRSpilling(false), SGPRInitBug(false), IsGCN(false),
       GCN1Encoding(false), GCN3Encoding(false), CIInsts(false), LDSBankCount(0),
Index: lib/Target/AMDGPU/SIRegisterInfo.cpp
===================================================================
--- lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -37,13 +37,17 @@
   const AMDGPUSubtarget &ST = MF.getSubtarget<AMDGPUSubtarget>();
   if (ST.hasSGPRInitBug()) {
     unsigned BaseIdx = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 4 - 4;
+    if (ST.isXNACKEnabled())
+      BaseIdx -= 4;
+
     unsigned BaseReg(AMDGPU::SGPR_32RegClass.getRegister(BaseIdx));
     return getMatchingSuperReg(BaseReg, AMDGPU::sub0, &AMDGPU::SReg_128RegClass);
   }
 
   if (ST.getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS) {
-    // 98/99 need to be reserved for flat_scr, and 100/101 for vcc. This is the
-    // next sgpr128 down.
+    // 98/99 need to be reserved for flat_scr or 96/97 for flat_scr and
+    // 98/99 for xnack_mask, and 100/101 for vcc. This is the next sgpr128 down
+    // either way.
     return AMDGPU::SGPR92_SGPR93_SGPR94_SGPR95;
   }
 
@@ -54,13 +58,25 @@
   const MachineFunction &MF) const {
   const AMDGPUSubtarget &ST = MF.getSubtarget<AMDGPUSubtarget>();
   if (ST.hasSGPRInitBug()) {
-    unsigned Idx = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 4 - 5;
+    unsigned Idx;
+
+    if (!ST.isXNACKEnabled())
+      Idx = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 4 - 5;
+    else
+      Idx = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 6 - 1;
+
     return AMDGPU::SGPR_32RegClass.getRegister(Idx);
   }
 
   if (ST.getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS) {
-    // Next register before reservations for flat_scr and vcc.
-    return AMDGPU::SGPR97;
+    if (!ST.isXNACKEnabled()) {
+      // Next register before reservations for flat_scr and vcc.
+      return AMDGPU::SGPR97;
+    } else {
+      // Next register before reservations for flat_scr, xnack_mask, vcc,
+      // and scratch resource.
+      return AMDGPU::SGPR91;
+    }
   }
 
   return AMDGPU::SGPR95;
@@ -86,6 +102,9 @@
     // for VCC/FLAT_SCR.
     reserveRegisterTuples(Reserved, AMDGPU::SGPR98_SGPR99);
     reserveRegisterTuples(Reserved, AMDGPU::SGPR100_SGPR101);
+
+    if (ST.isXNACKEnabled())
+      reserveRegisterTuples(Reserved, AMDGPU::SGPR96_SGPR97);
   }
 
   // Tonga and Iceland can only allocate a fixed number of SGPRs due
@@ -93,9 +112,11 @@
   if (ST.hasSGPRInitBug()) {
     unsigned NumSGPRs = AMDGPU::SGPR_32RegClass.getNumRegs();
     // Reserve some SGPRs for FLAT_SCRATCH and VCC (4 SGPRs).
-    // Assume XNACK_MASK is unused.
     unsigned Limit = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 4;
 
+    if (ST.isXNACKEnabled())
+      Limit -= 2;
+
     for (unsigned i = Limit; i < NumSGPRs; ++i) {
       unsigned Reg = AMDGPU::SGPR_32RegClass.getRegister(i);
       reserveRegisterTuples(Reserved, Reg);
Index: test/CodeGen/AMDGPU/flat-scratch-reg.ll
===================================================================
--- test/CodeGen/AMDGPU/flat-scratch-reg.ll
+++ test/CodeGen/AMDGPU/flat-scratch-reg.ll
@@ -1,8 +1,10 @@
-; RUN: llc < %s -march=amdgcn -mcpu=kaveri -verify-machineinstrs | FileCheck %s --check-prefix=GCN --check-prefix=CI
-; RUN: llc < %s -march=amdgcn -mcpu=fiji -verify-machineinstrs | FileCheck %s --check-prefix=GCN --check-prefix=VI
+; RUN: llc < %s -march=amdgcn -mcpu=kaveri -verify-machineinstrs | FileCheck %s --check-prefix=GCN --check-prefix=CI --check-prefix=NO-XNACK
+; RUN: llc < %s -march=amdgcn -mcpu=fiji -verify-machineinstrs | FileCheck %s --check-prefix=GCN --check-prefix=VI --check-prefix=NO-XNACK
+; RUN: llc < %s -march=amdgcn -mcpu=carrizo -mattr=+xnack -verify-machineinstrs | FileCheck %s --check-prefix=GCN --check-prefix=XNACK
 
 ; GCN-LABEL: {{^}}no_vcc_no_flat:
-; GCN: ; NumSgprs: 8
+; NO-XNACK: ; NumSgprs: 8
+; XNACK: ; NumSgprs: 12
 define void @no_vcc_no_flat() {
 entry:
   call void asm sideeffect "", "~{SGPR7}"()
@@ -10,7 +12,8 @@
 }
 
 ; GCN-LABEL: {{^}}vcc_no_flat:
-; GCN: ; NumSgprs: 10
+; NO-XNACK: ; NumSgprs: 10
+; XNACK: ; NumSgprs: 12
 define void @vcc_no_flat() {
 entry:
   call void asm sideeffect "", "~{SGPR7},~{VCC}"()
@@ -19,7 +22,8 @@
 
 ; GCN-LABEL: {{^}}no_vcc_flat:
 ; CI: ; NumSgprs: 12
-; VI: ; NumSgprs: 14
+; VI: ; NumSgprs: 12
+; XNACK: ; NumSgprs: 14
 define void @no_vcc_flat() {
 entry:
   call void asm sideeffect "", "~{SGPR7},~{FLAT_SCR}"()
@@ -28,7 +32,8 @@
 
 ; GCN-LABEL: {{^}}vcc_flat:
 ; CI: ; NumSgprs: 12
-; VI: ; NumSgprs: 14
+; VI: ; NumSgprs: 12
+; XNACK: ; NumSgprs: 14
 define void @vcc_flat() {
 entry:
   call void asm sideeffect "", "~{SGPR7},~{VCC},~{FLAT_SCR}"()