[llvm] r312318 - Debug info for variables whose type is shrinked to bool

[Strahinja Petrovic via llvm-commits]

Author: spetrovic
Date: Fri Sep  1 03:05:27 2017
New Revision: 312318

URL: http://llvm.org/viewvc/llvm-project?rev=312318&view=rev
Log:
Debug info for variables whose type is shrinked to bool

This patch provides such debug information for integer
variables whose type is shrinked to bool by providing 
dwarf expression which returns either constant initial 
value or other value.

Patch by Nikola Prica.

Differential Revision: https://reviews.llvm.org/D35994

Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
    llvm/trunk/lib/IR/DebugInfoMetadata.cpp
    llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp?rev=312318&r1=312317&r2=312318&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp Fri Sep  1 03:05:27 2017
@@ -338,6 +338,7 @@ void DwarfExpression::addExpression(DIEx
       break;
     case dwarf::DW_OP_plus:
     case dwarf::DW_OP_minus:
+    case dwarf::DW_OP_mul:
       emitOp(Op->getOp());
       break;
     case dwarf::DW_OP_deref:

Modified: llvm/trunk/lib/IR/DebugInfoMetadata.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DebugInfoMetadata.cpp?rev=312318&r1=312317&r2=312318&view=diff
==============================================================================
--- llvm/trunk/lib/IR/DebugInfoMetadata.cpp (original)
+++ llvm/trunk/lib/IR/DebugInfoMetadata.cpp Fri Sep  1 03:05:27 2017
@@ -643,6 +643,7 @@ bool DIExpression::isValid() const {
     case dwarf::DW_OP_plus_uconst:
     case dwarf::DW_OP_plus:
     case dwarf::DW_OP_minus:
+    case dwarf::DW_OP_mul:
     case dwarf::DW_OP_deref:
     case dwarf::DW_OP_xderef:
       break;

Modified: llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp?rev=312318&r1=312317&r2=312318&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/GlobalOpt.cpp Fri Sep  1 03:05:27 2017
@@ -36,6 +36,7 @@
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/ValueHandle.h"
+#include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -1603,12 +1604,47 @@ static bool TryToShrinkGlobalToBoolean(G
   assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
          "No reason to shrink to bool!");
 
+  SmallVector<DIGlobalVariableExpression *, 1> GVs;
+  GV->getDebugInfo(GVs);
+
   // If initialized to zero and storing one into the global, we can use a cast
   // instead of a select to synthesize the desired value.
   bool IsOneZero = false;
-  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
+  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)){
     IsOneZero = InitVal->isNullValue() && CI->isOne();
 
+    ConstantInt *CIInit = dyn_cast<ConstantInt>(GV->getInitializer());
+    uint64_t ValInit = CIInit->getZExtValue();
+    uint64_t ValOther = CI->getZExtValue();
+    uint64_t ValMinus = ValOther - ValInit;
+
+    for(auto *GVe : GVs){
+      DIGlobalVariable *DGV = GVe->getVariable();
+      DIExpression *E = GVe->getExpression();
+
+      // val * (ValOther - ValInit) + ValInit:
+      // DW_OP_deref DW_OP_constu <ValMinus>
+      // DW_OP_mul DW_OP_constu <ValInit> DW_OP_plus DW_OP_stack_value
+      E = DIExpression::get(NewGV->getContext(),
+                           {dwarf::DW_OP_deref,
+                            dwarf::DW_OP_constu,
+                            ValMinus,
+                            dwarf::DW_OP_mul,
+                            dwarf::DW_OP_constu,
+                            ValInit,
+                            dwarf::DW_OP_plus,
+                            dwarf::DW_OP_stack_value});
+      DIGlobalVariableExpression *DGVE =
+        DIGlobalVariableExpression::get(NewGV->getContext(), DGV, E);
+      NewGV->addDebugInfo(DGVE);
+    }
+  } else {
+    // FIXME: This will only emit address for debugger on which will
+    // be written only 0 or 1.
+    for(auto *GV : GVs)
+      NewGV->addDebugInfo(GV);
+  }
+
   while (!GV->use_empty()) {
     Instruction *UI = cast<Instruction>(GV->user_back());
     if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {