1 files changed, 138 insertions, 0 deletions
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyDebugFixup.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyDebugFixup.cpp
new file mode 100644
index 0000000000000..655e30a29eff4
--- /dev/null
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyDebugFixup.cpp
@@ -0,0 +1,138 @@
+//===-- WebAssemblyDebugFixup.cpp - Debug Fixup ------------------===//
+//
+// 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
+/// Several prior passes may "stackify" registers, here we ensure any references
+/// in such registers in debug_value instructions become stack relative also.
+/// This is done in a separate pass such that not all previous passes need to
+/// track stack depth when values get stackified.
+///
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssembly.h"
+#include "WebAssemblyMachineFunctionInfo.h"
+#include "WebAssemblySubtarget.h"
+#include "WebAssemblyUtilities.h"
+#include "llvm/ADT/SCCIterator.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineLoopInfo.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-debug-fixup"
+
+namespace {
+class WebAssemblyDebugFixup final : public MachineFunctionPass {
+  StringRef getPassName() const override { return "WebAssembly Debug Fixup"; }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
+    MachineFunctionPass::getAnalysisUsage(AU);
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+public:
+  static char ID; // Pass identification, replacement for typeid
+  WebAssemblyDebugFixup() : MachineFunctionPass(ID) {}
+};
+} // end anonymous namespace
+
+char WebAssemblyDebugFixup::ID = 0;
+INITIALIZE_PASS(
+    WebAssemblyDebugFixup, DEBUG_TYPE,
+    "Ensures debug_value's that have been stackified become stack relative",
+    false, false)
+
+FunctionPass *llvm::createWebAssemblyDebugFixup() {
+  return new WebAssemblyDebugFixup();
+}
+
+bool WebAssemblyDebugFixup::runOnMachineFunction(MachineFunction &MF) {
+  LLVM_DEBUG(dbgs() << "********** Debug Fixup **********\n"
+                       "********** Function: "
+                    << MF.getName() << '\n');
+
+  WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
+  const auto *TII = MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+
+  struct StackElem {
+    unsigned Reg;
+    MachineInstr *DebugValue;
+  };
+  std::vector<StackElem> Stack;
+  for (MachineBasicBlock &MBB : MF) {
+    // We may insert into this list.
+    for (auto MII = MBB.begin(); MII != MBB.end(); ++MII) {
+      MachineInstr &MI = *MII;
+      if (MI.isDebugValue()) {
+        auto &MO = MI.getOperand(0);
+        // Also check if not a $noreg: likely a DBG_VALUE we just inserted.
+        if (MO.isReg() && MO.getReg().isValid() &&
+            MFI.isVRegStackified(MO.getReg())) {
+          // Found a DBG_VALUE with a stackified register we will
+          // change into a stack operand.
+          // Search for register rather than assume it is on top (which it
+          // typically is if it appears right after the def), since
+          // DBG_VALUE's may shift under some circumstances.
+          for (auto &Elem : reverse(Stack)) {
+            if (MO.getReg() == Elem.Reg) {
+              auto Depth = static_cast<unsigned>(&Elem - &Stack[0]);
+              LLVM_DEBUG(dbgs() << "Debug Value VReg " << MO.getReg()
+                                << " -> Stack Relative " << Depth << "\n");
+              MO.ChangeToTargetIndex(WebAssembly::TI_OPERAND_STACK, Depth);
+              // Save the DBG_VALUE instruction that defined this stackified
+              // variable since later we need it to construct another one on
+              // pop.
+              Elem.DebugValue = &MI;
+              break;
+            }
+          }
+          // If the Reg was not found, we have a DBG_VALUE outside of its
+          // def-use range, and we leave it unmodified as reg, which means
+          // it will be culled later.
+        }
+      } else {
+        // Track stack depth.
+        for (MachineOperand &MO : reverse(MI.explicit_uses())) {
+          if (MO.isReg() && MFI.isVRegStackified(MO.getReg())) {
+            auto Prev = Stack.back();
+            Stack.pop_back();
+            assert(Prev.Reg == MO.getReg() &&
+                   "WebAssemblyDebugFixup: Pop: Register not matched!");
+            if (Prev.DebugValue) {
+              // This stackified reg is a variable that started life at
+              // Prev.DebugValue, so now that we're popping it we must insert
+              // a $noreg DBG_VALUE for the variable to end it, right after
+              // the current instruction.
+              BuildMI(*Prev.DebugValue->getParent(), std::next(MII),
+                      Prev.DebugValue->getDebugLoc(), TII->get(WebAssembly::DBG_VALUE), false,
+                      Register(), Prev.DebugValue->getOperand(2).getMetadata(),
+                      Prev.DebugValue->getOperand(3).getMetadata());
+            }
+          }
+        }
+        for (MachineOperand &MO : MI.defs()) {
+          if (MO.isReg() && MFI.isVRegStackified(MO.getReg())) {
+            Stack.push_back({MO.getReg(), nullptr});
+          }
+        }
+      }
+    }
+    assert(Stack.empty() &&
+           "WebAssemblyDebugFixup: Stack not empty at end of basic block!");
+  }
+
+  return true;
+}