1 files changed, 261 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp b/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
new file mode 100644
index 000000000000..5299068efdd4
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+++ b/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyFrameLowering.cpp
@@ -0,0 +1,261 @@
+//===-- WebAssemblyFrameLowering.cpp - WebAssembly Frame Lowering ----------==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the WebAssembly implementation of
+/// TargetFrameLowering class.
+///
+/// On WebAssembly, there aren't a lot of things to do here. There are no
+/// callee-saved registers to save, and no spill slots.
+///
+/// The stack grows downward.
+///
+//===----------------------------------------------------------------------===//
+
+#include "WebAssemblyFrameLowering.h"
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssemblyInstrInfo.h"
+#include "WebAssemblyMachineFunctionInfo.h"
+#include "WebAssemblySubtarget.h"
+#include "WebAssemblyTargetMachine.h"
+#include "WebAssemblyUtilities.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineModuleInfoImpls.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/Support/Debug.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "wasm-frame-info"
+
+// TODO: wasm64
+// TODO: Emit TargetOpcode::CFI_INSTRUCTION instructions
+
+/// We need a base pointer in the case of having items on the stack that
+/// require stricter alignment than the stack pointer itself.  Because we need
+/// to shift the stack pointer by some unknown amount to force the alignment,
+/// we need to record the value of the stack pointer on entry to the function.
+bool WebAssemblyFrameLowering::hasBP(const MachineFunction &MF) const {
+  const auto *RegInfo =
+      MF.getSubtarget<WebAssemblySubtarget>().getRegisterInfo();
+  return RegInfo->needsStackRealignment(MF);
+}
+
+/// Return true if the specified function should have a dedicated frame pointer
+/// register.
+bool WebAssemblyFrameLowering::hasFP(const MachineFunction &MF) const {
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+
+  // When we have var-sized objects, we move the stack pointer by an unknown
+  // amount, and need to emit a frame pointer to restore the stack to where we
+  // were on function entry.
+  // If we already need a base pointer, we use that to fix up the stack pointer.
+  // If there are no fixed-size objects, we would have no use of a frame
+  // pointer, and thus should not emit one.
+  bool HasFixedSizedObjects = MFI.getStackSize() > 0;
+  bool NeedsFixedReference = !hasBP(MF) || HasFixedSizedObjects;
+
+  return MFI.isFrameAddressTaken() ||
+         (MFI.hasVarSizedObjects() && NeedsFixedReference) ||
+         MFI.hasStackMap() || MFI.hasPatchPoint();
+}
+
+/// Under normal circumstances, when a frame pointer is not required, we reserve
+/// argument space for call sites in the function immediately on entry to the
+/// current function. This eliminates the need for add/sub sp brackets around
+/// call sites. Returns true if the call frame is included as part of the stack
+/// frame.
+bool WebAssemblyFrameLowering::hasReservedCallFrame(
+    const MachineFunction &MF) const {
+  return !MF.getFrameInfo().hasVarSizedObjects();
+}
+
+// Returns true if this function needs a local user-space stack pointer for its
+// local frame (not for exception handling).
+bool WebAssemblyFrameLowering::needsSPForLocalFrame(
+    const MachineFunction &MF) const {
+  auto &MFI = MF.getFrameInfo();
+  return MFI.getStackSize() || MFI.adjustsStack() || hasFP(MF);
+}
+
+// In function with EH pads, we need to make a copy of the value of
+// __stack_pointer global in SP32 register, in order to use it when restoring
+// __stack_pointer after an exception is caught.
+bool WebAssemblyFrameLowering::needsPrologForEH(
+    const MachineFunction &MF) const {
+  auto EHType = MF.getTarget().getMCAsmInfo()->getExceptionHandlingType();
+  return EHType == ExceptionHandling::Wasm &&
+         MF.getFunction().hasPersonalityFn() && MF.getFrameInfo().hasCalls();
+}
+
+/// Returns true if this function needs a local user-space stack pointer.
+/// Unlike a machine stack pointer, the wasm user stack pointer is a global
+/// variable, so it is loaded into a register in the prolog.
+bool WebAssemblyFrameLowering::needsSP(const MachineFunction &MF) const {
+  return needsSPForLocalFrame(MF) || needsPrologForEH(MF);
+}
+
+/// Returns true if the local user-space stack pointer needs to be written back
+/// to __stack_pointer global by this function (this is not meaningful if
+/// needsSP is false). If false, the stack red zone can be used and only a local
+/// SP is needed.
+bool WebAssemblyFrameLowering::needsSPWriteback(
+    const MachineFunction &MF) const {
+  auto &MFI = MF.getFrameInfo();
+  assert(needsSP(MF));
+  // When we don't need a local stack pointer for its local frame but only to
+  // support EH, we don't need to write SP back in the epilog, because we don't
+  // bump down the stack pointer in the prolog. We need to write SP back in the
+  // epilog only if
+  // 1. We need SP not only for EH support but also because we actually use
+  // stack or we have a frame address taken.
+  // 2. We cannot use the red zone.
+  bool CanUseRedZone = MFI.getStackSize() <= RedZoneSize && !MFI.hasCalls() &&
+                       !MF.getFunction().hasFnAttribute(Attribute::NoRedZone);
+  return needsSPForLocalFrame(MF) && !CanUseRedZone;
+}
+
+void WebAssemblyFrameLowering::writeSPToGlobal(
+    unsigned SrcReg, MachineFunction &MF, MachineBasicBlock &MBB,
+    MachineBasicBlock::iterator &InsertStore, const DebugLoc &DL) const {
+  const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+
+  const char *ES = "__stack_pointer";
+  auto *SPSymbol = MF.createExternalSymbolName(ES);
+  BuildMI(MBB, InsertStore, DL, TII->get(WebAssembly::GLOBAL_SET_I32))
+      .addExternalSymbol(SPSymbol)
+      .addReg(SrcReg);
+}
+
+MachineBasicBlock::iterator
+WebAssemblyFrameLowering::eliminateCallFramePseudoInstr(
+    MachineFunction &MF, MachineBasicBlock &MBB,
+    MachineBasicBlock::iterator I) const {
+  assert(!I->getOperand(0).getImm() && (hasFP(MF) || hasBP(MF)) &&
+         "Call frame pseudos should only be used for dynamic stack adjustment");
+  const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+  if (I->getOpcode() == TII->getCallFrameDestroyOpcode() &&
+      needsSPWriteback(MF)) {
+    DebugLoc DL = I->getDebugLoc();
+    writeSPToGlobal(WebAssembly::SP32, MF, MBB, I, DL);
+  }
+  return MBB.erase(I);
+}
+
+void WebAssemblyFrameLowering::emitPrologue(MachineFunction &MF,
+                                            MachineBasicBlock &MBB) const {
+  // TODO: Do ".setMIFlag(MachineInstr::FrameSetup)" on emitted instructions
+  auto &MFI = MF.getFrameInfo();
+  assert(MFI.getCalleeSavedInfo().empty() &&
+         "WebAssembly should not have callee-saved registers");
+
+  if (!needsSP(MF))
+    return;
+  uint64_t StackSize = MFI.getStackSize();
+
+  const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+  auto &MRI = MF.getRegInfo();
+
+  auto InsertPt = MBB.begin();
+  while (InsertPt != MBB.end() &&
+         WebAssembly::isArgument(InsertPt->getOpcode()))
+    ++InsertPt;
+  DebugLoc DL;
+
+  const TargetRegisterClass *PtrRC =
+      MRI.getTargetRegisterInfo()->getPointerRegClass(MF);
+  unsigned SPReg = WebAssembly::SP32;
+  if (StackSize)
+    SPReg = MRI.createVirtualRegister(PtrRC);
+
+  const char *ES = "__stack_pointer";
+  auto *SPSymbol = MF.createExternalSymbolName(ES);
+  BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::GLOBAL_GET_I32), SPReg)
+      .addExternalSymbol(SPSymbol);
+
+  bool HasBP = hasBP(MF);
+  if (HasBP) {
+    auto FI = MF.getInfo<WebAssemblyFunctionInfo>();
+    unsigned BasePtr = MRI.createVirtualRegister(PtrRC);
+    FI->setBasePointerVreg(BasePtr);
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::COPY), BasePtr)
+        .addReg(SPReg);
+  }
+  if (StackSize) {
+    // Subtract the frame size
+    unsigned OffsetReg = MRI.createVirtualRegister(PtrRC);
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
+        .addImm(StackSize);
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::SUB_I32),
+            WebAssembly::SP32)
+        .addReg(SPReg)
+        .addReg(OffsetReg);
+  }
+  if (HasBP) {
+    unsigned BitmaskReg = MRI.createVirtualRegister(PtrRC);
+    unsigned Alignment = MFI.getMaxAlignment();
+    assert((1u << countTrailingZeros(Alignment)) == Alignment &&
+           "Alignment must be a power of 2");
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), BitmaskReg)
+        .addImm((int)~(Alignment - 1));
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::AND_I32),
+            WebAssembly::SP32)
+        .addReg(WebAssembly::SP32)
+        .addReg(BitmaskReg);
+  }
+  if (hasFP(MF)) {
+    // Unlike most conventional targets (where FP points to the saved FP),
+    // FP points to the bottom of the fixed-size locals, so we can use positive
+    // offsets in load/store instructions.
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::COPY), WebAssembly::FP32)
+        .addReg(WebAssembly::SP32);
+  }
+  if (StackSize && needsSPWriteback(MF)) {
+    writeSPToGlobal(WebAssembly::SP32, MF, MBB, InsertPt, DL);
+  }
+}
+
+void WebAssemblyFrameLowering::emitEpilogue(MachineFunction &MF,
+                                            MachineBasicBlock &MBB) const {
+  uint64_t StackSize = MF.getFrameInfo().getStackSize();
+  if (!needsSP(MF) || !needsSPWriteback(MF))
+    return;
+  const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+  auto &MRI = MF.getRegInfo();
+  auto InsertPt = MBB.getFirstTerminator();
+  DebugLoc DL;
+
+  if (InsertPt != MBB.end())
+    DL = InsertPt->getDebugLoc();
+
+  // Restore the stack pointer. If we had fixed-size locals, add the offset
+  // subtracted in the prolog.
+  unsigned SPReg = 0;
+  if (hasBP(MF)) {
+    auto FI = MF.getInfo<WebAssemblyFunctionInfo>();
+    SPReg = FI->getBasePointerVreg();
+  } else if (StackSize) {
+    const TargetRegisterClass *PtrRC =
+        MRI.getTargetRegisterInfo()->getPointerRegClass(MF);
+    unsigned OffsetReg = MRI.createVirtualRegister(PtrRC);
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::CONST_I32), OffsetReg)
+        .addImm(StackSize);
+    // In the epilog we don't need to write the result back to the SP32 physreg
+    // because it won't be used again. We can use a stackified register instead.
+    SPReg = MRI.createVirtualRegister(PtrRC);
+    BuildMI(MBB, InsertPt, DL, TII->get(WebAssembly::ADD_I32), SPReg)
+        .addReg(hasFP(MF) ? WebAssembly::FP32 : WebAssembly::SP32)
+        .addReg(OffsetReg);
+  } else {
+    SPReg = hasFP(MF) ? WebAssembly::FP32 : WebAssembly::SP32;
+  }
+
+  writeSPToGlobal(SPReg, MF, MBB, InsertPt, DL);
+}