[WebAssembly] Support for register stackifying with load and store instructions.

[oota-llvm.git] / lib / Target / WebAssembly / WebAssemblyStoreResults.cpp

diff --git a/lib/Target/WebAssembly/WebAssemblyStoreResults.cpp b/lib/Target/WebAssembly/WebAssemblyStoreResults.cpp
new file mode 100644 (file)
index 0000000..d0735b8
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+++ b/lib/Target/WebAssembly/WebAssemblyStoreResults.cpp
@@ -0,0 +1,102 @@
+//===-- WebAssemblyStoreResults.cpp - Optimize using store result values --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file implements an optimization pass using store result values.
+///
+/// WebAssembly's store instructions return the stored value, specifically to
+/// enable the optimization of reducing get_local/set_local traffic, which is
+/// what we're doing here.
+///
+//===----------------------------------------------------------------------===//
+
+#include "WebAssembly.h"
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssemblyMachineFunctionInfo.h"
+#include "WebAssemblySubtarget.h"
+#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "wasm-store-results"
+
+namespace {
+class WebAssemblyStoreResults final : public MachineFunctionPass {
+public:
+  static char ID; // Pass identification, replacement for typeid
+  WebAssemblyStoreResults() : MachineFunctionPass(ID) {}
+
+  const char *getPassName() const override {
+    return "WebAssembly Store Results";
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    AU.addRequired<MachineBlockFrequencyInfo>();
+    AU.addPreserved<MachineBlockFrequencyInfo>();
+    AU.addRequired<MachineDominatorTree>();
+    AU.addPreserved<MachineDominatorTree>();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+private:
+};
+} // end anonymous namespace
+
+char WebAssemblyStoreResults::ID = 0;
+FunctionPass *llvm::createWebAssemblyStoreResults() {
+  return new WebAssemblyStoreResults();
+}
+
+bool WebAssemblyStoreResults::runOnMachineFunction(MachineFunction &MF) {
+  DEBUG({
+    dbgs() << "********** Store Results **********\n"
+           << "********** Function: " << MF.getName() << '\n';
+  });
+
+  const MachineRegisterInfo &MRI = MF.getRegInfo();
+  MachineDominatorTree &MDT = getAnalysis<MachineDominatorTree>();
+
+  for (auto &MBB : MF)
+    for (auto &MI : MBB)
+      switch (MI.getOpcode()) {
+      default:
+        break;
+      case WebAssembly::STORE8_I32:
+      case WebAssembly::STORE16_I32:
+      case WebAssembly::STORE8_I64:
+      case WebAssembly::STORE16_I64:
+      case WebAssembly::STORE32_I64:
+      case WebAssembly::STORE_F32:
+      case WebAssembly::STORE_F64:
+      case WebAssembly::STORE_I32:
+      case WebAssembly::STORE_I64:
+        unsigned ToReg = MI.getOperand(0).getReg();
+        unsigned FromReg = MI.getOperand(2).getReg();
+        for (auto I = MRI.use_begin(FromReg), E = MRI.use_end(); I != E;) {
+          MachineOperand &O = *I++;
+          MachineInstr *Where = O.getParent();
+          if (Where->getOpcode() == TargetOpcode::PHI)
+            Where = Where->getOperand(&O - &Where->getOperand(0) + 1)
+                        .getMBB()
+                        ->getFirstTerminator();
+          if (&MI == Where || !MDT.dominates(&MI, Where))
+            continue;
+          O.setReg(ToReg);
+        }
+      }
+
+  return true;
+}