[AMDGPU] Do not assume a default GCN target

[arsenm]

lib/Basic/Targets/AMDGPU.cpp

188–189

I think this needs to distinguish no specified target from an invalid cpu name

[rampitec]

lib/Basic/Targets/AMDGPU.cpp

188–189

It does. clang then exits with "error: unknown target CPU":

clang -cc1 -triple amdgcn-amd-amdhsa -target-cpu invalid gas.cl
error: unknown target CPU 'invalid'
note: valid target CPU values are: gfx600, tahiti, gfx601, hainan, oland, pitcairn, verde, gfx700, kaveri, gfx701, hawaii, gfx702, gfx703, kabini, mullins, gfx704, bonaire, gfx801, carrizo, gfx802, iceland, tonga, gfx803, fiji, polaris10, polaris11, gfx810, stoney, gfx900, gfx902, gfx904, gfx906, gfx908, gfx909, gfx1010, gfx1011, gfx1012

[arsenm]

LGTM

lib/Basic/Targets/AMDGPU.cpp

 bool AMDGPUTargetInfo::initFeatureMap(
     llvm::StringMap<bool> &Features, DiagnosticsEngine &Diags, StringRef CPU,
     const std::vector<std::string> &FeatureVec) const {
 
   using namespace llvm::AMDGPU;
 
   // XXX - What does the member GPU mean if device name string passed here?
   if (isAMDGCN(getTriple())) {
-    if (CPU.empty())
-      CPU = "gfx600";
-
     switch (llvm::AMDGPU::parseArchAMDGCN(CPU)) {
     case GK_GFX1012:
     case GK_GFX1011:
       Features["dot1-insts"] = true;
       Features["dot2-insts"] = true;
       Features["dot5-insts"] = true;
       Features["dot6-insts"] = true;
       LLVM_FALLTHROUGH;
if (isAMDGCN(getTriple())) {
     case GK_GFX702:
     case GK_GFX701:
     case GK_GFX700:
       Features["ci-insts"] = true;
       LLVM_FALLTHROUGH;
     case GK_GFX601:
     case GK_GFX600:
       break;
     case GK_NONE:
-      return false;
+      break;
     default:
       llvm_unreachable("Unhandled GPU!");
     }
   } else {
     if (CPU.empty())
       CPU = "r600";
 
     switch (llvm::AMDGPU::parseArchR600(CPU)) {

test/Driver/amdgpu-mcpu.cl

 // CAICOS:  "-target-cpu" "caicos"
 // CAYMAN:  "-target-cpu" "cayman"
 // TURKS:   "-target-cpu" "turks"
 
 //
 // AMDGCN-based processors.
 //
 
+// RUN: %clang -### -target amdgcn %s 2>&1 | FileCheck --check-prefix=GCNDEFAULT %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx600 %s 2>&1 | FileCheck --check-prefix=GFX600 %s
 // RUN: %clang -### -target amdgcn -mcpu=tahiti %s 2>&1 | FileCheck --check-prefix=TAHITI %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx601 %s 2>&1 | FileCheck --check-prefix=GFX601 %s
 // RUN: %clang -### -target amdgcn -mcpu=hainan %s 2>&1 | FileCheck --check-prefix=HAINAN %s
 // RUN: %clang -### -target amdgcn -mcpu=oland %s 2>&1 | FileCheck --check-prefix=OLAND %s
 // RUN: %clang -### -target amdgcn -mcpu=pitcairn %s 2>&1 | FileCheck --check-prefix=PITCAIRN %s
 // RUN: %clang -### -target amdgcn -mcpu=verde %s 2>&1 | FileCheck --check-prefix=VERDE %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx700 %s 2>&1 | FileCheck --check-prefix=GFX700 %s

 // RUN: %clang -### -target amdgcn -mcpu=gfx904 %s 2>&1 | FileCheck --check-prefix=GFX904 %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx906 %s 2>&1 | FileCheck --check-prefix=GFX906 %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx908 %s 2>&1 | FileCheck --check-prefix=GFX908 %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx909 %s 2>&1 | FileCheck --check-prefix=GFX909 %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx1010 %s 2>&1 | FileCheck --check-prefix=GFX1010 %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx1011 %s 2>&1 | FileCheck --check-prefix=GFX1011 %s
 // RUN: %clang -### -target amdgcn -mcpu=gfx1012 %s 2>&1 | FileCheck --check-prefix=GFX1012 %s
 
+// GCNDEFAULT-NOT: -target-cpu
 // GFX600:    "-target-cpu" "gfx600"
 // TAHITI:    "-target-cpu" "tahiti"
 // GFX601:    "-target-cpu" "gfx601"
 // HAINAN:    "-target-cpu" "hainan"
 // OLAND:     "-target-cpu" "oland"
 // PITCAIRN:  "-target-cpu" "pitcairn"
 // VERDE:     "-target-cpu" "verde"
 // GFX700:    "-target-cpu" "gfx700"