1 files changed, 151 insertions, 0 deletions
diff --git a/llvm/lib/Target/X86/X86InsertWait.cpp b/llvm/lib/Target/X86/X86InsertWait.cpp
new file mode 100644
index 000000000000..a82d98d88b30
--- /dev/null
+++ b/llvm/lib/Target/X86/X86InsertWait.cpp
@@ -0,0 +1,151 @@
+//-  X86Insertwait.cpp - Strict-Fp:Insert wait instruction X87 instructions --//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the pass which insert x86 wait instructions after each
+// X87 instructions when strict float is enabled.
+//
+// The logic to insert a wait instruction after an X87 instruction is as below:
+// 1. If the X87 instruction don't raise float exception nor is a load/store
+//    instruction, or is a x87 control instruction, don't insert wait.
+// 2. If the X87 instruction is an instruction which the following instruction
+//    is an X87 exception synchronizing X87 instruction, don't insert wait.
+// 3. For other situations, insert wait instruction.
+//
+//===----------------------------------------------------------------------===//
+
+#include "X86.h"
+#include "X86InstrInfo.h"
+#include "X86Subtarget.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/IR/DebugLoc.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "x86-insert-wait"
+
+namespace {
+
+class WaitInsert : public MachineFunctionPass {
+public:
+  static char ID;
+
+  WaitInsert() : MachineFunctionPass(ID) {}
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  StringRef getPassName() const override {
+    return "X86 insert wait instruction";
+  }
+
+private:
+  const TargetInstrInfo *TII; // Machine instruction info.
+};
+
+} // namespace
+
+char WaitInsert::ID = 0;
+
+FunctionPass *llvm::createX86InsertX87waitPass() { return new WaitInsert(); }
+
+/// Return true if the Reg is X87 register.
+static bool isX87Reg(unsigned Reg) {
+  return (Reg == X86::FPCW || Reg == X86::FPSW ||
+          (Reg >= X86::ST0 && Reg <= X86::ST7));
+}
+
+/// check if the instruction is X87 instruction
+static bool isX87Instruction(MachineInstr &MI) {
+  for (const MachineOperand &MO : MI.operands()) {
+    if (!MO.isReg())
+      continue;
+    if (isX87Reg(MO.getReg()))
+      return true;
+  }
+  return false;
+}
+
+static bool isX87ControlInstruction(MachineInstr &MI) {
+  switch (MI.getOpcode()) {
+  case X86::FNINIT:
+  case X86::FLDCW16m:
+  case X86::FNSTCW16m:
+  case X86::FNSTSW16r:
+  case X86::FNSTSWm:
+  case X86::FNCLEX:
+  case X86::FLDENVm:
+  case X86::FSTENVm:
+  case X86::FRSTORm:
+  case X86::FSAVEm:
+  case X86::FINCSTP:
+  case X86::FDECSTP:
+  case X86::FFREE:
+  case X86::FFREEP:
+  case X86::FNOP:
+  case X86::WAIT:
+    return true;
+  default:
+    return false;
+  }
+}
+
+static bool isX87NonWaitingControlInstruction(MachineInstr &MI) {
+  // a few special control instructions don't perform a wait operation
+  switch (MI.getOpcode()) {
+  case X86::FNINIT:
+  case X86::FNSTSW16r:
+  case X86::FNSTSWm:
+  case X86::FNSTCW16m:
+  case X86::FNCLEX:
+    return true;
+  default:
+    return false;
+  }
+}
+
+bool WaitInsert::runOnMachineFunction(MachineFunction &MF) {
+  if (!MF.getFunction().hasFnAttribute(Attribute::StrictFP))
+    return false;
+
+  const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
+  TII = ST.getInstrInfo();
+  bool Changed = false;
+
+  for (MachineBasicBlock &MBB : MF) {
+    for (MachineBasicBlock::iterator MI = MBB.begin(); MI != MBB.end(); ++MI) {
+      // Jump non X87 instruction.
+      if (!isX87Instruction(*MI))
+        continue;
+      // If the instruction instruction neither has float exception nor is
+      // a load/store instruction, or the instruction is x87 control
+      // instruction, do not insert wait.
+      if (!(MI->mayRaiseFPException() || MI->mayLoadOrStore()) ||
+          isX87ControlInstruction(*MI))
+        continue;
+      // If the following instruction is an X87 instruction and isn't an X87
+      // non-waiting control instruction, we can omit insert wait instruction.
+      MachineBasicBlock::iterator AfterMI = std::next(MI);
+      if (AfterMI != MBB.end() && isX87Instruction(*AfterMI) &&
+          !isX87NonWaitingControlInstruction(*AfterMI))
+        continue;
+
+      BuildMI(MBB, AfterMI, MI->getDebugLoc(), TII->get(X86::WAIT));
+      LLVM_DEBUG(dbgs() << "\nInsert wait after:\t" << *MI);
+      // Jump the newly inserting wait
+      ++MI;
+      Changed = true;
+    }
+  }
+  return Changed;
+}