From b544a1017753bfef7b91a2ea3024ffbde6cd5bb9 Mon Sep 17 00:00:00 2001
From: Artem Serov <artem.serov@arm.com>
Date: Mon, 7 Oct 2024 13:48:54 +0100
Subject: Arm64: Fix PackedSwitch codegen for large methods.

This patch fixes a bug in arm64 PackedSwitch code generation
for very large methods where we exceeded the range of Adr
instruction - jump tables were emited in the very end of the
method. Instead we now emit the jump table in-place as part of
the PackedSwitch visitor - in the same way how it is done
in arm32 backend.

This patch also removes an incorrect assumption that the size of
a method has a linear dependency on the number of its HIR
instructions. This was used to choose whether to emit a jump
table for a PackedSwitch.

Test: art/test.py --target --host --optimizing
Test: art/test.py --gtest art_compiler_tests

Change-Id: I0795811a6408a25021879ab6be9e23ef5f1f50e4
---
 compiler/optimizing/codegen_test.cc | 67 +++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

(limited to 'compiler/optimizing/codegen_test.cc')

diff --git a/compiler/optimizing/codegen_test.cc b/compiler/optimizing/codegen_test.cc
index 7365f0fb7f..14a419fcd8 100644
--- a/compiler/optimizing/codegen_test.cc
+++ b/compiler/optimizing/codegen_test.cc
@@ -73,6 +73,7 @@ class CodegenTest : public CommonCompilerTest, public OptimizingUnitTestHelper {
                       int64_t j,
                       DataType::Type type,
                       const CodegenTargetConfig target_config);
+  void TestPackedSwitch(const CodegenTargetConfig target_config);
 };
 
 void CodegenTest::TestCode(const std::vector<uint16_t>& data, bool has_result, int32_t expected) {
@@ -682,6 +683,72 @@ TEST_F(CodegenTest, ComparisonsLong) {
   }
 }
 
+// Tests a PackedSwitch in a very large HGraph; validates that the switch jump table is in
+// range for the PC-relative load in the codegen visitor.
+void CodegenTest::TestPackedSwitch(const CodegenTargetConfig target_config) {
+  HBasicBlock* return_block = InitEntryMainExitGraph();
+  constexpr DataType::Type data_type = DataType::Type::kInt32;
+
+  // A number of entries - we are interested to test jump table implementation.
+  constexpr size_t kNumSwitchEntries = 10;
+
+  // Number of jump targets (including a 'default' case).
+  constexpr size_t kNumBB = kNumSwitchEntries + 1;
+  // Some arbitrary value to be used as input.
+  constexpr int kInputValue = kNumBB - 4;
+
+  HInstruction* input = graph_->GetIntConstant(kInputValue);
+  HIntConstant* constant_1 = graph_->GetIntConstant(1);
+
+  HBasicBlock* switch_block = AddNewBlock();
+  entry_block_->ReplaceSuccessor(return_block, switch_block);
+
+  HPackedSwitch* hswitch = new (GetAllocator()) HPackedSwitch(0, kNumSwitchEntries, input);
+  switch_block->AddInstruction(hswitch);
+
+  std::vector<HInstruction*> phi_inputs {};
+
+  // Add switch jump target blocks.
+  for (int i = 0; i < kNumBB; i++) {
+    HBasicBlock* case_block = AddNewBlock();
+    case_block->AddPredecessor(switch_block);
+    case_block->AddSuccessor(return_block);
+
+    HIntConstant* case_value = graph_->GetIntConstant(i);
+    HAdd* add = MakeBinOp<HAdd>(case_block, data_type, input, case_value);
+    phi_inputs.emplace_back(add);
+
+    MakeGoto(case_block);
+  }
+
+  HPhi* phi = MakePhi(return_block, phi_inputs);
+  HInstruction* return_val = phi;
+
+  // Emit a huge number of HAdds - to simulate a very large HGraph.
+  constexpr int kNumOfAdds = 2 * 1024 * 1024;
+  for (int i = 0; i < kNumOfAdds; i++) {
+    return_val = MakeBinOp<HAdd>(return_block, data_type, return_val, constant_1);
+  }
+
+  MakeReturn(return_block, return_val);
+
+  graph_->BuildDominatorTree();
+  EXPECT_TRUE(CheckGraph());
+
+  std::unique_ptr<CompilerOptions> compiler_options =
+      CommonCompilerTest::CreateCompilerOptions(target_config.GetInstructionSet(), "default");
+  RunCode(target_config,
+          *compiler_options,
+          graph_,
+          [](HGraph*) {}, true, kNumOfAdds + 2 * kInputValue);
+}
+
+TEST_F(CodegenTest, PackedSwitchInHugeMethod) {
+  for (CodegenTargetConfig target_config : GetTargetConfigs()) {
+    TestPackedSwitch(target_config);
+  }
+}
+
 #ifdef ART_ENABLE_CODEGEN_arm
 TEST_F(CodegenTest, ARMVIXLParallelMoveResolver) {
   std::unique_ptr<CompilerOptions> compiler_options =
-- 
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