[llvm] [NVPTX] Fix code generation for `trap-unreachable`. (PR #67478)

[Artem Belevich via llvm-commits]

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@@ -99,12 +105,33 @@ char NVPTXLowerUnreachable::ID = 1;
 INITIALIZE_PASS(NVPTXLowerUnreachable, "nvptx-lower-unreachable",
                 "Lower Unreachable", false, false)
 
+StringRef NVPTXLowerUnreachable::getPassName() const {
+  return "add an exit instruction before every unreachable";
+}
+
+// =============================================================================
+// Returns whether a `trap` intrinsic should be emitted before I.
+//
+// This is a copy of the logic in SelectionDAGBuilder::visitUnreachable().
+// =============================================================================
+bool NVPTXLowerUnreachable::isLoweredToTrap(const UnreachableInst &I) const {
+  if (!TrapUnreachable)
+    return false;
+  if (!NoTrapAfterNoreturn)
+    return true;
+  const CallInst *Call = dyn_cast_or_null<CallInst>(I.getPrevNode());
+  return Call && Call->doesNotReturn();
+}
+
 // =============================================================================
 // Main function for this pass.
 // =============================================================================
 bool NVPTXLowerUnreachable::runOnFunction(Function &F) {
   if (skipFunction(F))
     return false;
+  // Early out iff isLoweredToTrap() always returns true.
+  if (TrapUnreachable && !NoTrapAfterNoreturn)
----------------
Artem-B wrote:

Nit: `!NoTrapAfterNoReturn` has disturbingly high concentration of negations. :-/
Can we rename it into `TrapAfterNoReturn` ?


https://github.com/llvm/llvm-project/pull/67478