[llvm] [SPIR-V] Add pass to merge convergence region exit targets (PR #92531)

[Ilia Diachkov via llvm-commits]

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@@ -0,0 +1,290 @@
+//===-- SPIRVMergeRegionExitTargets.cpp ----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Merge the multiple exit targets of a convergence region into a single block.
+// Each exit target will be assigned a constant value, and a phi node + switch
+// will allow the new exit target to re-route to the correct basic block.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Analysis/SPIRVConvergenceRegionAnalysis.h"
+#include "SPIRV.h"
+#include "SPIRVSubtarget.h"
+#include "SPIRVTargetMachine.h"
+#include "SPIRVUtils.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/CodeGen/IntrinsicLowering.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/IntrinsicsSPIRV.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/LoopSimplify.h"
+#include "llvm/Transforms/Utils/LowerMemIntrinsics.h"
+
+using namespace llvm;
+
+namespace llvm {
+void initializeSPIRVMergeRegionExitTargetsPass(PassRegistry &);
+} // namespace llvm
+
+namespace llvm {
+
+class SPIRVMergeRegionExitTargets : public FunctionPass {
+public:
+  static char ID;
+
+  SPIRVMergeRegionExitTargets() : FunctionPass(ID) {
+    initializeSPIRVMergeRegionExitTargetsPass(*PassRegistry::getPassRegistry());
+  };
+
+  // Gather all the successors of |BB|.
+  // This function asserts if the terminator neither a branch, switch or return.
+  std::unordered_set<BasicBlock *> gatherSuccessors(BasicBlock *BB) {
+    std::unordered_set<BasicBlock *> output;
+    auto *T = BB->getTerminator();
+
+    if (auto *BI = dyn_cast<BranchInst>(T)) {
+      output.insert(BI->getSuccessor(0));
+      if (BI->isConditional())
+        output.insert(BI->getSuccessor(1));
+      return output;
+    }
+
+    if (auto *SI = dyn_cast<SwitchInst>(T)) {
+      output.insert(SI->getDefaultDest());
+      for (auto &Case : SI->cases()) {
+        output.insert(Case.getCaseSuccessor());
+      }
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iliya-diyachkov wrote:

Maybe don't need braces here.

https://github.com/llvm/llvm-project/pull/92531