[CUDA] Die if we ask the NVPTX backend to emit a global ctor/dtor.

[jlebar]

Summary

Previously we'd just silently skip these.

[tra]

Looks OK to me, but I'd run it by someone familiar with back-end.

lib/Target/NVPTX/NVPTXAsmPrinter.cpp

808 ↗

(On Diff #46442)

I'd make it an assert so we know if/when llvm.global_ctors mutates into something we can't deal with.

[jholewinski]

LGTM. Thanks!

[jlebar]

lib/Target/NVPTX/NVPTXAsmPrinter.cpp

808 ↗

(On Diff #46442)

That was my inclination as well, but in AsmPrinter, this is not an error, so I'm not sure it should be one here.

https://github.com/llvm-project/llvm-project/blob/49e3b4837314fc2920616c36287aa23e4e4be6fc/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp#L1568

[tra]

LGTM.

lib/Target/NVPTX/NVPTXAsmPrinter.cpp

808 ↗

(On Diff #46442)

OK. We'll probably catch it when we generate something ptxas can't handle.

llvm/trunk/lib/Target/NVPTX/NVPTXAsmPrinter.cpp

for (DISubprogram *SP : DbgFinder.subprograms()) {
     }
     if (filenameMap.find(Filename) != filenameMap.end())
       continue;
     filenameMap[Filename] = i;
     ++i;
   }
 }
 
+static bool isEmptyXXStructor(GlobalVariable *GV) {
+  if (!GV) return true;
+  const ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
+  if (!InitList) return true;  // Not an array; we don't know how to parse.
+  return InitList->getNumOperands() == 0;
+}
+
 bool NVPTXAsmPrinter::doInitialization(Module &M) {
   // Construct a default subtarget off of the TargetMachine defaults. The
   // rest of NVPTX isn't friendly to change subtargets per function and
   // so the default TargetMachine will have all of the options.
   const Triple &TT = TM.getTargetTriple();
   StringRef CPU = TM.getTargetCPU();
   StringRef FS = TM.getTargetFeatureString();
   const NVPTXTargetMachine &NTM = static_cast<const NVPTXTargetMachine &>(TM);
   const NVPTXSubtarget STI(TT, CPU, FS, NTM);
 
   if (M.alias_size()) {
     report_fatal_error("Module has aliases, which NVPTX does not support.");
     return true; // error
   }
+  if (!isEmptyXXStructor(M.getNamedGlobal("llvm.global_ctors"))) {
+    report_fatal_error(
+        "Module has a nontrivial global ctor, which NVPTX does not support.");
+    return true;  // error
+  }
+  if (!isEmptyXXStructor(M.getNamedGlobal("llvm.global_dtors"))) {
+    report_fatal_error(
+        "Module has a nontrivial global dtor, which NVPTX does not support.");
+    return true;  // error
+  }
 
   SmallString<128> Str1;
   raw_svector_ostream OS1(Str1);
 
   MMI = getAnalysisIfAvailable<MachineModuleInfo>();
 
   // We need to call the parent's one explicitly.
   //bool Result = AsmPrinter::doInitialization(M);

llvm/trunk/test/CodeGen/NVPTX/global-ctor-empty.ll

+; RUN: llc < %s -march=nvptx -mcpu=sm_20 2>&1
+
+; Check that llc doesn't die when given an empty global ctor / dtor.
[e-mail]_ctors = appending global [0 x { i32, void ()*, i8* }] []
[e-mail]_dtors = appending global [0 x { i32, void ()*, i8* }] []

llvm/trunk/test/CodeGen/NVPTX/global-ctor.ll

+; RUN: not llc < %s -march=nvptx -mcpu=sm_20 2>&1 | FileCheck %s
+
+; Check that llc dies when given a nonempty global ctor.
[e-mail]_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @foo, i8* null }]
+
+; CHECK: ERROR: Module has a nontrivial global ctor
+define internal void @foo() {
+  ret void
+}

llvm/trunk/test/CodeGen/NVPTX/global-dtor.ll

+; RUN: not llc < %s -march=nvptx -mcpu=sm_20 2>&1 | FileCheck %s
+
+; Check that llc dies when given a nonempty global dtor.
[e-mail]_dtors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @foo, i8* null }]
+
+; CHECK: ERROR: Module has a nontrivial global dtor
+define internal void @foo() {
+  ret void
+}