[NVPTX] added a hidden option to control NVPTXLowerUnreachable pass.

[tra]

Summary

We've ran into an issue where the pass breaks a handful of our internal tests
and need a way to temporarily disable the pass while we're investigating.

[alexfh]

Looks good as a temporary measure.

llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp

66

Could you add a FIXME to get rid of this eventually?

414

nit: Looks like a tab character. clang-format, please

[alexfh]

llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp

414

IIUC, pre-merge checks are complaining about formatting: https://buildkite.com/llvm-project/premerge-checks/builds/161426#01890803-0fee-40a1-a9b3-d1d55a200ede

[tra]

Addressed comments. Reformatted the changes.

[tra]

llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp

414

This is odd. It's all-spaces in my source file. Here's hexdump of that part of the diff:

00000590  6c 65 50 61 73 73 28 29  29 3b 0a 2b 20 20 69 66  |lePass());.+  if|
000005a0  20 28 45 78 69 74 4f 6e  55 6e 72 65 61 63 68 61  | (ExitOnUnreacha|
000005b0  62 6c 65 29 0a 2b 20 20  20 20 61 64 64 50 61 73  |ble).+    addPas|
000005c0  73 28 63 72 65 61 74 65  4e 56 50 54 58 4c 6f 77  |s(createNVPTXLow|
000005d0  65 72 55 6e 72 65 61 63  68 61 62 6c 65 50 61 73  |erUnreachablePas|

[tra]

clang-formatted whole file.

llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp

static cl::opt<bool> DisableRequireStructuredCFG(
     cl::init(false), cl::Hidden);
 
 static cl::opt<bool> UseShortPointersOpt(
     "nvptx-short-ptr",
     cl::desc(
         "Use 32-bit pointers for accessing const/local/shared address spaces."),
     cl::init(false), cl::Hidden);
 
+// FIXME: intended as a temporary debugging aid. Should be removed before it
+// makes it into the LLVM-17 release.
+static cl::opt<bool>
+    ExitOnUnreachable("nvptx-exit-on-unreachable",
+                      cl::desc("Lower 'unreachable' as 'exit' instruction."),
+                      cl::init(true), cl::Hidden);
+
 namespace llvm {
 
 void initializeGenericToNVVMLegacyPassPass(PassRegistry &);
 void initializeNVPTXAllocaHoistingPass(PassRegistry &);
 void initializeNVPTXAssignValidGlobalNamesPass(PassRegistry&);
 void initializeNVPTXAtomicLowerPass(PassRegistry &);
 void initializeNVPTXCtorDtorLoweringLegacyPass(PassRegistry &);
 void initializeNVPTXLowerAggrCopiesPass(PassRegistry &);
void NVPTXPassConfig::addIRPasses() {
   // but EarlyCSE can do neither of them.
   if (getOptLevel() != CodeGenOpt::None) {
     addEarlyCSEOrGVNPass();
     if (!DisableLoadStoreVectorizer)
       addPass(createLoadStoreVectorizerPass());
     addPass(createSROAPass());
   }
 
+  if (ExitOnUnreachable)
     addPass(createNVPTXLowerUnreachablePass());
 }
 
 bool NVPTXPassConfig::addInstSelector() {
   const NVPTXSubtarget &ST = *getTM<NVPTXTargetMachine>().getSubtargetImpl();
 
   addPass(createLowerAggrCopies());
   addPass(createAllocaHoisting());
   addPass(createNVPTXISelDag(getNVPTXTargetMachine(), getOptLevel()));