RFC: [AMDGPU] Check subtarget features for consistency (#86957)

Implement GCNSubtarget::checkSubtargetFeatures as a canonical place to
check subtarget features for consistency and diagnose any
inconsistencies. To start with, the implementation just checks that
either wavefrontsize32 or wavefrontsize64 is selected.

checkSubtargetFeatures is called at the start of instruction selection.
This is pretty arbitrary. It is just a convenient point at which we have
access to the subtarget that we're going to use for codegenning a
particular function.

Author: jayfoad

llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp

@@ -132,6 +132,7 @@ bool AMDGPUDAGToDAGISel::runOnMachineFunction(MachineFunction &MF) {
   }
 #endif
   Subtarget = &MF.getSubtarget<GCNSubtarget>();
+  Subtarget->checkSubtargetFeatures(MF.getFunction());
   Mode = SIModeRegisterDefaults(MF.getFunction(), *Subtarget);
   return SelectionDAGISel::runOnMachineFunction(MF);
 }

llvm/lib/Target/AMDGPU/AMDGPUInstructionSelector.cpp

@@ -63,6 +63,7 @@ void AMDGPUInstructionSelector::setupMF(MachineFunction &MF, GISelKnownBits *KB,
                                         BlockFrequencyInfo *BFI) {
   MRI = &MF.getRegInfo();
   Subtarget = &MF.getSubtarget<GCNSubtarget>();
+  Subtarget->checkSubtargetFeatures(MF.getFunction());
   InstructionSelector::setupMF(MF, KB, CoverageInfo, PSI, BFI);
 }
 

llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp

@@ -25,6 +25,7 @@
 #include "llvm/CodeGen/GlobalISel/InlineAsmLowering.h"
 #include "llvm/CodeGen/MachineScheduler.h"
 #include "llvm/CodeGen/TargetFrameLowering.h"
+#include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/IntrinsicsAMDGPU.h"
 #include "llvm/IR/IntrinsicsR600.h"
 #include "llvm/IR/MDBuilder.h"
@@ -165,6 +166,15 @@ GCNSubtarget::initializeSubtargetDependencies(const Triple &TT,
   return *this;
 }
 
+void GCNSubtarget::checkSubtargetFeatures(const Function &F) const {
+  LLVMContext &Ctx = F.getContext();
+  if (hasFeature(AMDGPU::FeatureWavefrontSize32) ==
+      hasFeature(AMDGPU::FeatureWavefrontSize64)) {
+    Ctx.diagnose(DiagnosticInfoUnsupported(
+        F, "must specify exactly one of wavefrontsize32 and wavefrontsize64"));
+  }
+}
+
 AMDGPUSubtarget::AMDGPUSubtarget(const Triple &TT) : TargetTriple(TT) {}
 
 bool AMDGPUSubtarget::useRealTrue16Insts() const {

llvm/lib/Target/AMDGPU/GCNSubtarget.h

@@ -250,6 +250,10 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   GCNSubtarget &initializeSubtargetDependencies(const Triple &TT,
                                                    StringRef GPU, StringRef FS);
 
+  /// Diagnose inconsistent subtarget features before attempting to codegen
+  /// function \p F.
+  void checkSubtargetFeatures(const Function &F) const;
+
   const SIInstrInfo *getInstrInfo() const override {
     return &InstrInfo;
   }

llvm/test/CodeGen/AMDGPU/check-subtarget-features.ll

@@ -0,0 +1,10 @@
+; RUN: not llc -global-isel=0 -mtriple=amdgcn -mcpu=gfx1100 -mattr=-wavefrontsize32,-wavefrontsize64 < %s 2>&1 | FileCheck %s -check-prefix=ERR -implicit-check-not=error:
+; RUN: not llc -global-isel=1 -mtriple=amdgcn -mcpu=gfx1100 -mattr=-wavefrontsize32,-wavefrontsize64 < %s 2>&1 | FileCheck %s -check-prefix=ERR -implicit-check-not=error:
+; RUN: not llc -global-isel=0 -mtriple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+wavefrontsize64 < %s 2>&1 | FileCheck %s -check-prefix=ERR -implicit-check-not=error:
+; RUN: not llc -global-isel=1 -mtriple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize32,+wavefrontsize64 < %s 2>&1 | FileCheck %s -check-prefix=ERR -implicit-check-not=error:
+
+; ERR: error: {{.*}} in function f void (): must specify exactly one of wavefrontsize32 and wavefrontsize64
+
+define void @f() {
+  ret void
+}

llvm/test/CodeGen/AMDGPU/remove-incompatible-wave32-feature.ll

@@ -8,13 +8,13 @@
 ; RUN: FileCheck --check-prefix=WARN-GFX90A %s < %t
 ; RUN: llc -mtriple=amdgcn -mcpu=gfx90a -mattr=+wavefrontsize64 -verify-machineinstrs < %s
 
-; RUN: llc -mtriple=amdgcn -mcpu=gfx1011 -mattr=+wavefrontsize64 -stop-after=amdgpu-remove-incompatible-functions\
+; RUN: llc -mtriple=amdgcn -mcpu=gfx1011 -mattr=-wavefrontsize32,+wavefrontsize64 -stop-after=amdgpu-remove-incompatible-functions\
 ; RUN:   -pass-remarks=amdgpu-remove-incompatible-functions < %s 2>%t | FileCheck -check-prefixes=GFX10 %s
-; RUN: llc -mtriple=amdgcn -mcpu=gfx1011 -mattr=+wavefrontsize64 -verify-machineinstrs < %s
+; RUN: llc -mtriple=amdgcn -mcpu=gfx1011 -mattr=-wavefrontsize32,+wavefrontsize64 -verify-machineinstrs < %s
 
-; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize64 -stop-after=amdgpu-remove-incompatible-functions\
+; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=-wavefrontsize32,+wavefrontsize64 -stop-after=amdgpu-remove-incompatible-functions\
 ; RUN:   -pass-remarks=amdgpu-remove-incompatible-functions < %s 2>%t | FileCheck -check-prefixes=GFX11 %s
-; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=+wavefrontsize64 -verify-machineinstrs < %s
+; RUN: llc -mtriple=amdgcn -mcpu=gfx1100 -mattr=-wavefrontsize32,+wavefrontsize64 -verify-machineinstrs < %s
 
 ; WARN-GFX906: removing function 'needs_wavefrontsize32': +wavefrontsize32 is not supported on the current target
 ; WARN-GFX906-NOT: not supported

llvm/test/CodeGen/AMDGPU/unknown-processor.ll

@@ -1,4 +1,4 @@
-; RUN: llc -mtriple=amdgcn-- -mcpu=unknown -verify-machineinstrs < %s 2>&1 | FileCheck -check-prefix=ERROR -check-prefix=GCN %s
+; RUN: not llc -mtriple=amdgcn-- -mcpu=unknown -verify-machineinstrs < %s 2>&1 | FileCheck -check-prefix=ERROR -check-prefix=GCN %s
 ; RUN: llc -mtriple=r600-- -mcpu=unknown -verify-machineinstrs < %s 2>&1 | FileCheck -check-prefix=ERROR -check-prefix=R600 %s
 target datalayout = "A5"