[AMDGPU] Always reserve flat scratch SGPR for architected flat scratch

[rampitec]

Summary

With architected flat scratch it becomes readonly. We must always
reserve SGPR pair for it even if we do not use scratch at all since
an attempt to write to SGPRs mapped to FLAT_SCRATCH results in
memory violation.

This is not needed since GFX10 with architected flat scratch though
since special SGPRs are not carving space from normal SGPRs.

[kzhuravl]

LGTM, thanks!

llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp

unsigned GCNSubtarget::getOccupancyWithNumVGPRs(unsigned VGPRs) const {
   return std::min(std::max(getTotalNumVGPRs() / RoundedRegs, 1u), MaxWaves);
 }
 
 unsigned
 GCNSubtarget::getBaseReservedNumSGPRs(const bool HasFlatScratchInit) const {
   if (getGeneration() >= AMDGPUSubtarget::GFX10)
     return 2; // VCC. FLAT_SCRATCH and XNACK are no longer in SGPRs.
 
-  if (HasFlatScratchInit) {
+  if (HasFlatScratchInit || HasArchitectedFlatScratch) {
     if (getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS)
       return 6; // FLAT_SCRATCH, XNACK, VCC (in that order).
     if (getGeneration() == AMDGPUSubtarget::SEA_ISLANDS)
       return 4; // FLAT_SCRATCH, VCC (in that order).
   }
 
   if (isXNACKEnabled())
     return 4; // XNACK, VCC (in that order).

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

unsigned getNumExtraSGPRs(const MCSubtargetInfo *STI, bool VCCUsed,
 
   if (Version.Major < 8) {
     if (FlatScrUsed)
       ExtraSGPRs = 4;
   } else {
     if (XNACKUsed)
       ExtraSGPRs = 4;
 
-    if (FlatScrUsed)
+    if (FlatScrUsed ||
+        STI->getFeatureBits().test(AMDGPU::FeatureArchitectedFlatScratch))
       ExtraSGPRs = 6;
   }
 
   return ExtraSGPRs;
 }
 
 unsigned getNumExtraSGPRs(const MCSubtargetInfo *STI, bool VCCUsed,
                           bool FlatScrUsed) {

llvm/test/CodeGen/AMDGPU/flat-scratch-reg.ll

 ; RUN: llc -march=amdgcn -mcpu=kaveri -verify-machineinstrs < %s | FileCheck -check-prefix=CI -check-prefix=GCN %s
 ; RUN: llc -march=amdgcn -mcpu=fiji -mattr=-xnack -verify-machineinstrs < %s | FileCheck -check-prefix=VI-NOXNACK -check-prefix=GCN %s
 
 ; RUN: llc -march=amdgcn -mcpu=carrizo -mattr=-xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=VI-NOXNACK,GCN %s
 ; RUN: llc -march=amdgcn -mcpu=stoney -mattr=-xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=VI-NOXNACK,GCN %s
 
 ; RUN: llc -march=amdgcn -mcpu=carrizo -mattr=+xnack -verify-machineinstrs < %s | FileCheck -check-prefix=VI-XNACK  -check-prefix=GCN %s
 ; RUN: llc -march=amdgcn -mcpu=stoney -mattr=+xnack -verify-machineinstrs < %s | FileCheck -check-prefix=VI-XNACK  -check-prefix=GCN %s
 
 ; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=kaveri --amdhsa-code-object-version=2 -verify-machineinstrs < %s | FileCheck -check-prefixes=CI,HSA-CI-V2,GCN %s
 ; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=carrizo --amdhsa-code-object-version=2 -mattr=+xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=VI-XNACK,HSA-VI-XNACK-V2,GCN %s
 
 ; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=kaveri -verify-machineinstrs < %s | FileCheck -check-prefixes=GCN %s
 ; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=carrizo -mattr=-xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=VI-NOXNACK,HSA-VI-NOXNACK,GCN %s
 ; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=carrizo -mattr=+xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=VI-XNACK,HSA-VI-XNACK,GCN %s
 
+; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=gfx900 -mattr=+architected-flat-scratch -verify-machineinstrs < %s | FileCheck -check-prefixes=GCN %s
+; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=gfx900 -mattr=+architected-flat-scratch,-xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=HSA-VI-NOXNACK,GFX9-ARCH-FLAT,GCN %s
+; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=gfx900 -mattr=+architected-flat-scratch,+xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=HSA-VI-XNACK,GFX9-ARCH-FLAT,GCN %s
+
+; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=gfx1010 -mattr=+architected-flat-scratch -verify-machineinstrs < %s | FileCheck -check-prefixes=GCN %s
+; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=gfx1010 -mattr=+architected-flat-scratch,-xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=HSA-VI-NOXNACK,GFX10-ARCH-FLAT,GCN %s
+; RUN: llc -march=amdgcn -mtriple=amdgcn--amdhsa -mcpu=gfx1010 -mattr=+architected-flat-scratch,+xnack -verify-machineinstrs < %s | FileCheck -check-prefixes=HSA-VI-XNACK,GFX10-ARCH-FLAT,GCN %s
+
 ; GCN-LABEL: {{^}}no_vcc_no_flat:
 
 ; HSA-CI-V2: is_xnack_enabled = 0
 ; HSA-VI-XNACK-V2: is_xnack_enabled = 1
 
 ; NOT-HSA-CI: .amdhsa_reserve_xnack_mask
 ; HSA-VI-NOXNACK: .amdhsa_reserve_xnack_mask 0
 ; HSA-VI-XNACK: .amdhsa_reserve_xnack_mask 1
 
 ; CI: ; NumSgprs: 8
 ; VI-NOXNACK: ; NumSgprs: 8
 ; VI-XNACK: ; NumSgprs: 12
+; GFX9-ARCH-FLAT: ; NumSgprs: 14
+; GFX10-ARCH-FLAT: ; NumSgprs: 8
 define amdgpu_kernel void @no_vcc_no_flat() {
 entry:
   call void asm sideeffect "", "~{s7}"()
   ret void
 }
 
 ; GCN-LABEL: {{^}}vcc_no_flat:
 
 ; HSA-CI-V2: is_xnack_enabled = 0
 ; HSA-VI-XNACK-V2: is_xnack_enabled = 1
 
 ; NOT-HSA-CI: .amdhsa_reserve_xnack_mask
 ; HSA-VI-NOXNACK: .amdhsa_reserve_xnack_mask 0
 ; HSA-VI-XNACK: .amdhsa_reserve_xnack_mask 1
 
 ; CI: ; NumSgprs: 10
 ; VI-NOXNACK: ; NumSgprs: 10
 ; VI-XNACK: ; NumSgprs: 12
+; GFX9-ARCH-FLAT: ; NumSgprs: 14
+; GFX10-ARCH-FLAT: ; NumSgprs: 10
 define amdgpu_kernel void @vcc_no_flat() {
 entry:
   call void asm sideeffect "", "~{s7},~{vcc}"()
   ret void
 }
 
 ; GCN-LABEL: {{^}}no_vcc_flat:
 
 ; HSA-CI-V2: is_xnack_enabled = 0
 ; HSA-VI-XNACK-V2: is_xnack_enabled = 1
 
 ; NOT-HSA-CI: .amdhsa_reserve_xnack_mask
 ; HSA-VI-NOXNACK: .amdhsa_reserve_xnack_mask 0
 ; HSA-VI-XNACK: .amdhsa_reserve_xnack_mask 1
 
 ; CI: ; NumSgprs: 12
 ; VI-NOXNACK: ; NumSgprs: 14
 ; VI-XNACK: ; NumSgprs: 14
+; GFX9-ARCH-FLAT: ; NumSgprs: 14
+; GFX10-ARCH-FLAT: ; NumSgprs: 8
 define amdgpu_kernel void @no_vcc_flat() {
 entry:
   call void asm sideeffect "", "~{s7},~{flat_scratch}"()
   ret void
 }
 
 ; GCN-LABEL: {{^}}vcc_flat:
 
 ; HSA-CI-V2: is_xnack_enabled = 0
 ; HSA-VI-XNACK-V2: is_xnack_enabled = 1
 
 ; NOT-HSA-CI: .amdhsa_reserve_xnack_mask
 ; HSA-VI-NOXNACK: .amdhsa_reserve_xnack_mask 0
 ; HSA-VI-XNACK: .amdhsa_reserve_xnack_mask 1
 
 ; CI: ; NumSgprs: 12
 ; VI-NOXNACK: ; NumSgprs: 14
 ; VI-XNACK: ; NumSgprs: 14
+; GFX9-ARCH-FLAT: ; NumSgprs: 14
+; GFX10-ARCH-FLAT: ; NumSgprs: 10
 define amdgpu_kernel void @vcc_flat() {
 entry:
   call void asm sideeffect "", "~{s7},~{vcc},~{flat_scratch}"()
   ret void
 }
 
 ; Make sure used SGPR count for flat_scr is correct when there is no
 ; scratch usage and implicit flat uses.
 
 ; GCN-LABEL: {{^}}use_flat_scr:
 
 ; HSA-CI-V2: is_xnack_enabled = 0
 ; HSA-VI-XNACK-V2: is_xnack_enabled = 1
 
 ; NOT-HSA-CI: .amdhsa_reserve_xnack_mask
 ; HSA-VI-NOXNACK: .amdhsa_reserve_xnack_mask 0
 ; HSA-VI-XNACK: .amdhsa_reserve_xnack_mask 1
 
 ; CI: NumSgprs: 4
 ; VI-NOXNACK: NumSgprs: 6
 ; VI-XNACK: NumSgprs: 6
+; GFX9-ARCH-FLAT: ; NumSgprs: 6
+; GFX10-ARCH-FLAT: ; NumSgprs: 0
 define amdgpu_kernel void @use_flat_scr() #0 {
 entry:
   call void asm sideeffect "; clobber ", "~{flat_scratch}"()
   ret void
 }
 
 ; GCN-LABEL: {{^}}use_flat_scr_lo:
 
 ; HSA-CI-V2: is_xnack_enabled = 0
 ; HSA-VI-XNACK-V2: is_xnack_enabled = 1
 
 ; NOT-HSA-CI: .amdhsa_reserve_xnack_mask
 ; HSA-VI-NOXNACK: .amdhsa_reserve_xnack_mask 0
 ; HSA-VI-XNACK: .amdhsa_reserve_xnack_mask 1
 
 ; CI: NumSgprs: 4
 ; VI-NOXNACK: NumSgprs: 6
 ; VI-XNACK: NumSgprs: 6
+; GFX9-ARCH-FLAT: ; NumSgprs: 6
+; GFX10-ARCH-FLAT: ; NumSgprs: 0
 define amdgpu_kernel void @use_flat_scr_lo() #0 {
 entry:
   call void asm sideeffect "; clobber ", "~{flat_scratch_lo}"()
   ret void
 }
 
 ; GCN-LABEL: {{^}}use_flat_scr_hi:
 
 ; HSA-CI-V2: is_xnack_enabled = 0
 ; HSA-VI-XNACK-V2: is_xnack_enabled = 1
 
 ; NOT-HSA-CI: .amdhsa_reserve_xnack_mask
 ; HSA-VI-NOXNACK: .amdhsa_reserve_xnack_mask 0
 ; HSA-VI-XNACK: .amdhsa_reserve_xnack_mask 1
 
 ; CI: NumSgprs: 4
 ; VI-NOXNACK: NumSgprs: 6
 ; VI-XNACK: NumSgprs: 6
+; GFX9-ARCH-FLAT: ; NumSgprs: 6
+; GFX10-ARCH-FLAT: ; NumSgprs: 0
 define amdgpu_kernel void @use_flat_scr_hi() #0 {
 entry:
   call void asm sideeffect "; clobber ", "~{flat_scratch_hi}"()
   ret void
 }
 
 attributes #0 = { nounwind }