From 707fb1cf0ca99d98c59f1ae87b7e0ff9b2dd0c8b Mon Sep 17 00:00:00 2001
From: Strahinja Petrovic <strahinja.petrovic@rt-rk.com>
Date: Fri, 1 Sep 2017 10:05:27 +0000
Subject: [PATCH] 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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312318 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/AsmPrinter/DwarfExpression.cpp |  1 +
 lib/IR/DebugInfoMetadata.cpp               |  1 +
 lib/Transforms/IPO/GlobalOpt.cpp           | 38 +++++++++++++++++++++-
 3 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 4538bb3ff02..429269d36d8 100644
--- a/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -338,6 +338,7 @@ void DwarfExpression::addExpression(DIExpressionCursor &&ExprCursor,
       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:
diff --git a/lib/IR/DebugInfoMetadata.cpp b/lib/IR/DebugInfoMetadata.cpp
index 005aac821f9..8f6822e3c97 100644
--- a/lib/IR/DebugInfoMetadata.cpp
+++ b/lib/IR/DebugInfoMetadata.cpp
@@ -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;
diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp
index ee8fdaebbda..8d4bde40968 100644
--- a/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/lib/Transforms/IPO/GlobalOpt.cpp
@@ -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(GlobalVariable *GV, Constant *OtherVal) {
   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)) {
-- 
2.50.1