[SelectionDAG][DebugInfo] Implement translation of entry_value vars

This commit implements SelectionDAG lowering of dbg.declare intrinsics targeting
swiftasync Arguments, by putting them in the MachineFunction's table of
variables whose location doesn't change throughout the function.

Depends on D149882

Differential Revision: https://reviews.llvm.org/D149883

Author: felipepiovezan

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@@ -1342,6 +1342,30 @@ static bool isFoldedOrDeadInstruction(const Instruction *I,
          !FuncInfo.isExportedInst(I); // Exported instrs must be computed.
 }
 
+static bool processIfEntryValueDbgDeclare(FunctionLoweringInfo &FuncInfo,
+                                          const Value *Arg, DIExpression *Expr,
+                                          DILocalVariable *Var,
+                                          DebugLoc DbgLoc) {
+  if (!Expr->isEntryValue() || !isa<Argument>(Arg))
+    return false;
+
+  auto ArgIt = FuncInfo.ValueMap.find(Arg);
+  if (ArgIt == FuncInfo.ValueMap.end())
+    return false;
+  Register ArgVReg = ArgIt->getSecond();
+
+  // Find the corresponding livein physical register to this argument.
+  for (auto [PhysReg, VirtReg] : FuncInfo.RegInfo->liveins())
+    if (VirtReg == ArgVReg) {
+      FuncInfo.MF->setVariableDbgInfo(Var, Expr, PhysReg, DbgLoc);
+      LLVM_DEBUG(dbgs() << "processDbgDeclare: setVariableDbgInfo Var=" << *Var
+                        << ", Expr=" << *Expr << ",  MCRegister=" << PhysReg
+                        << ", DbgLoc=" << DbgLoc << "\n");
+      return true;
+    }
+  return false;
+}
+
 static bool processDbgDeclare(FunctionLoweringInfo &FuncInfo,
                               const Value *Address, DIExpression *Expr,
                               DILocalVariable *Var, DebugLoc DbgLoc) {
@@ -1350,6 +1374,10 @@ static bool processDbgDeclare(FunctionLoweringInfo &FuncInfo,
                       << " (bad address)\n");
     return false;
   }
+
+  if (processIfEntryValueDbgDeclare(FuncInfo, Address, Expr, Var, DbgLoc))
+    return true;
+
   MachineFunction *MF = FuncInfo.MF;
   const DataLayout &DL = MF->getDataLayout();
 

llvm/test/CodeGen/AArch64/dbg-declare-swift-async.ll

@@ -1,4 +1,6 @@
 ; RUN: llc -O0 -global-isel -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s
+; RUN: llc -O0 -fast-isel -stop-after=finalize-isel %s -o - | FileCheck %s
+; RUN: llc -O0 -fast-isel=false -global-isel=false -stop-after=finalize-isel %s -o - | FileCheck %s
 
 ; CHECK: void @foo
 ; CHECK-NEXT: dbg.declare(metadata {{.*}}, metadata ![[VAR:.*]], metadata ![[EXPR:.*]]), !dbg ![[LOC:.*]]