[DebugInfo] More strict debug range for stack variables

Variable's stack location can stretch longer than it should. If a
variable is placed at the stack in a some nested basic block its range
can be calculated to be up to the next occurrence of the variable's
DBG_VALUE, or up to the end of the function, thus covering a basic
blocks that should not be included in the variable’s location range.
This happens because the DbgEntityHistoryCalculator ends register
locations at the end of a basic block only if the variable’s location
register has been changed throughout the function, which is not the
case for the register used to reference stack objects.

This patch also tries to produce a single value location if the location
list builder managed to merge all the locations into one.

Reviewers: aprantl, dstenb, jmorse

Reviewed By: aprantl, dstenb, jmorse

Subscribers: djtodoro, ivanbaev, asowda

Tags: #debug-info

Differential Revision: https://reviews.llvm.org/D61600

llvm-svn: 362923

1 files changed, 12 insertions, 21 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 45ae009b189..37e963ed63b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -607,36 +607,27 @@ DIE *DwarfCompileUnit::constructVariableDIEImpl(const DbgVariable &DV,
     return VariableDie;
   }
 
-  // Check if variable is described by a DBG_VALUE instruction.
-  if (const MachineInstr *DVInsn = DV.getMInsn()) {
-    assert(DVInsn->getNumOperands() == 4);
-    if (DVInsn->getOperand(0).isReg()) {
-      auto RegOp = DVInsn->getOperand(0);
-      auto Op1 = DVInsn->getOperand(1);
-      // If the second operand is an immediate, this is an indirect value.
-      assert((!Op1.isImm() || (Op1.getImm() == 0)) && "unexpected offset");
-      MachineLocation Location(RegOp.getReg(), Op1.isImm());
-      addVariableAddress(DV, *VariableDie, Location);
-    } else if (DVInsn->getOperand(0).isImm()) {
-      // This variable is described by a single constant.
-      // Check whether it has a DIExpression.
+  // Check if variable has a single location description.
+  if (auto *DVal = DV.getValueLoc()) {
+    if (DVal->isLocation())
+      addVariableAddress(DV, *VariableDie, DVal->getLoc());
+    else if (DVal->isInt()) {
       auto *Expr = DV.getSingleExpression();
       if (Expr && Expr->getNumElements()) {
         DIELoc *Loc = new (DIEValueAllocator) DIELoc;
         DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
         // If there is an expression, emit raw unsigned bytes.
         DwarfExpr.addFragmentOffset(Expr);
-        DwarfExpr.addUnsignedConstant(DVInsn->getOperand(0).getImm());
+        DwarfExpr.addUnsignedConstant(DVal->getInt());
         DwarfExpr.addExpression(Expr);
         addBlock(*VariableDie, dwarf::DW_AT_location, DwarfExpr.finalize());
       } else
-        addConstantValue(*VariableDie, DVInsn->getOperand(0), DV.getType());
-    } else if (DVInsn->getOperand(0).isFPImm())
-      addConstantFPValue(*VariableDie, DVInsn->getOperand(0));
-    else if (DVInsn->getOperand(0).isCImm())
-      addConstantValue(*VariableDie, DVInsn->getOperand(0).getCImm(),
-                       DV.getType());
-
+        addConstantValue(*VariableDie, DVal->getInt(), DV.getType());
+    } else if (DVal->isConstantFP()) {
+      addConstantFPValue(*VariableDie, DVal->getConstantFP());
+    } else if (DVal->isConstantInt()) {
+      addConstantValue(*VariableDie, DVal->getConstantInt(), DV.getType());
+    }
     return VariableDie;
   }