[llvm] [SPIRV] Add support for SPV_KHR_abort extension (PR #193037)

[Victor Mustya via llvm-commits]

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@@ -2253,6 +2253,29 @@ Instruction *SPIRVEmitIntrinsics::visitAtomicCmpXchgInst(AtomicCmpXchgInst &I) {
 Instruction *SPIRVEmitIntrinsics::visitUnreachableInst(UnreachableInst &I) {
   IRBuilder<> B(I.getParent());
   B.SetInsertPoint(&I);
+  // OpAbortKHR is itself a SPIR-V block terminator. If the immediately
+  // preceding instruction is a call to llvm.spv.abort, do not emit an
+  // additional OpUnreachable, which would leave the SPIR-V block with two
+  // terminators and produce invalid SPIR-V. The check is intentionally limited
+  // to the directly-preceding non-debug instruction: any real instruction
+  // sitting between `llvm.spv.abort` and `unreachable` would also be invalid
+  // SPIR-V (nothing can follow OpAbortKHR in the same block), so assert that
+  // shape if we see an `spv_abort` anywhere earlier in the block.
+  Instruction *Prev = I.getPrevNode();
+  while (Prev && Prev->isDebugOrPseudoInst())
+    Prev = Prev->getPrevNode();
+  if (auto *CI = dyn_cast_or_null<CallInst>(Prev);
+      CI && CI->getIntrinsicID() == Intrinsic::spv_abort)
+    return &I;
+#ifndef NDEBUG
+  for (Instruction *P = I.getPrevNode(); P; P = P->getPrevNode()) {
+    auto *CI = dyn_cast<CallInst>(P);
+    if (CI && CI->getIntrinsicID() == Intrinsic::spv_abort)
+      llvm_unreachable("llvm.spv.abort must be the last non-debug instruction "
+                       "before its block's `unreachable`; OpAbortKHR is itself "
+                       "a SPIR-V block terminator");
+  }
+#endif
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vmustya wrote:

I've implemented the handling on the stage, when the `__spirv_AbortKHR` built-in function is translated to the `llvm.spv.abort` intrinsic. Also, I've re-written the check to an assertion: https://github.com/llvm/llvm-project/pull/193037/commits/6bacaf143c6e2cb849a0b2bddb84a79a36f3cf49

https://github.com/llvm/llvm-project/pull/193037