Index: lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
+++ lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
@@ -417,16 +417,24 @@
     }
   }
 
-  if (VCCUsed || FlatUsed || STM.isXNACKEnabled()) {
-    MaxSGPR += 2;
+  unsigned ExtraSGPRs = 0;
 
-    if (FlatUsed)
-      MaxSGPR += 2;
+  if (VCCUsed)
+    ExtraSGPRs = 2;
 
+  if (STM.getGeneration() < AMDGPUSubtarget::VOLCANIC_ISLANDS) {
+    if (FlatUsed)
+      ExtraSGPRs = 4;
+  } else {
     if (STM.isXNACKEnabled())
-      MaxSGPR += 2;
+      ExtraSGPRs = 4;
+
+    if (FlatUsed)
+      ExtraSGPRs = 6;
   }
 
+  MaxSGPR += ExtraSGPRs;
+
   // We found the maximum register index. They start at 0, so add one to get the
   // number of registers.
   ProgInfo.NumVGPR = MaxVGPR + 1;
Index: lib/Target/AMDGPU/SIRegisterInfo.cpp
===================================================================
--- lib/Target/AMDGPU/SIRegisterInfo.cpp
+++ lib/Target/AMDGPU/SIRegisterInfo.cpp
@@ -36,18 +36,15 @@
   const MachineFunction &MF) const {
   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;
-
+    // Leave space for flat_scr, xnack_mask, vcc, and alignment
+    unsigned BaseIdx = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 8 - 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 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.
+    // 96/97 need to be reserved for flat_scr, 98/99 for xnack_mask, and
+    // 100/101 for vcc. This is the next sgpr128 down.
     return AMDGPU::SGPR92_SGPR93_SGPR94_SGPR95;
   }
 
@@ -58,25 +55,14 @@
   const MachineFunction &MF) const {
   const AMDGPUSubtarget &ST = MF.getSubtarget<AMDGPUSubtarget>();
   if (ST.hasSGPRInitBug()) {
-    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;
-
+    unsigned Idx = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 6 - 1;
     return AMDGPU::SGPR_32RegClass.getRegister(Idx);
   }
 
   if (ST.getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS) {
-    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;
-    }
+    // Next register before reservations for flat_scr, xnack_mask, vcc,
+    // and scratch resource.
+    return AMDGPU::SGPR91;
   }
 
   return AMDGPU::SGPR95;
@@ -99,23 +85,22 @@
 
   if (ST.getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS) {
     // SI/CI have 104 SGPRs. VI has 102. We need to shift down the reservation
-    // for VCC/FLAT_SCR.
+    // for VCC/XNACK_MASK/FLAT_SCR.
+    //
+    // TODO The SGPRs that alias to XNACK_MASK could be used as general purpose
+    // SGPRs when the XNACK feature is not used. This is currently not done
+    // because the code that counts SGPRs cannot account for such holes.
+    reserveRegisterTuples(Reserved, AMDGPU::SGPR96_SGPR97);
     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
   // to a hw bug.
   if (ST.hasSGPRInitBug()) {
     unsigned NumSGPRs = AMDGPU::SGPR_32RegClass.getNumRegs();
-    // Reserve some SGPRs for FLAT_SCRATCH and VCC (4 SGPRs).
-    unsigned Limit = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 4;
-
-    if (ST.isXNACKEnabled())
-      Limit -= 2;
+    // Reserve some SGPRs for FLAT_SCRATCH, XNACK_MASK, and VCC (6 SGPRs).
+    unsigned Limit = AMDGPUSubtarget::FIXED_SGPR_COUNT_FOR_INIT_BUG - 6;
 
     for (unsigned i = Limit; i < NumSGPRs; ++i) {
       unsigned Reg = AMDGPU::SGPR_32RegClass.getRegister(i);
Index: test/CodeGen/AMDGPU/flat-scratch-reg.ll
===================================================================
--- test/CodeGen/AMDGPU/flat-scratch-reg.ll
+++ test/CodeGen/AMDGPU/flat-scratch-reg.ll
@@ -1,6 +1,6 @@
 ; 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
+; RUN: llc < %s -march=amdgcn -mcpu=carrizo -mattr=+xnack -verify-machineinstrs | FileCheck %s --check-prefix=GCN --check-prefix=VI --check-prefix=XNACK
 
 ; GCN-LABEL: {{^}}no_vcc_no_flat:
 ; NO-XNACK: ; NumSgprs: 8
@@ -22,8 +22,7 @@
 
 ; GCN-LABEL: {{^}}no_vcc_flat:
 ; CI: ; NumSgprs: 12
-; VI: ; NumSgprs: 12
-; XNACK: ; NumSgprs: 14
+; VI: ; NumSgprs: 14
 define void @no_vcc_flat() {
 entry:
   call void asm sideeffect "", "~{SGPR7},~{FLAT_SCR}"()
@@ -32,8 +31,7 @@
 
 ; GCN-LABEL: {{^}}vcc_flat:
 ; CI: ; NumSgprs: 12
-; VI: ; NumSgprs: 12
-; XNACK: ; NumSgprs: 14
+; VI: ; NumSgprs: 14
 define void @vcc_flat() {
 entry:
   call void asm sideeffect "", "~{SGPR7},~{VCC},~{FLAT_SCR}"()