Debug info for variables whose type is shrinked to bool fix

[NikolaPrica]

Summary

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.

This patch contains fix for reverted commit rL312318 which was causing failure due to use of unchecked dyn_cast to CIInit.

[vsk]

Could you include an IR-based test case?

[aprantl]

lib/Transforms/IPO/GlobalOpt.cpp

1625

Since this is bound to confuse future readers, it wouldn't hurt to add a line explaining how this expression works.

1648

Why this restriction?

[aprantl]

thanks!

[NikolaPrica]

lib/Transforms/IPO/GlobalOpt.cpp

1648

This condition is necessary for examples like:

long a[];
static int b = a;

Previous version of this patch did not check for dyn_cast for CIInit which resulted in failure for the example above.

lib/CodeGen/AsmPrinter/DwarfExpression.cpp

while (ExprCursor) {
     }
     case dwarf::DW_OP_plus_uconst:
       assert(LocationKind != Register);
       emitOp(dwarf::DW_OP_plus_uconst);
       emitUnsigned(Op->getArg(0));
       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:
       assert(LocationKind != Register);
       if (LocationKind != Memory && isMemoryLocation(ExprCursor))
         // Turning this into a memory location description makes the deref
         // implicit.
         LocationKind = Memory;

lib/IR/DebugInfoMetadata.cpp

case dwarf::DW_OP_swap: {
       if (getNumElements() == 1)
         return false;
       break;
     }
     case dwarf::DW_OP_constu:
     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;
     }
   }
   return true;
 }
 

lib/Transforms/IPO/GlobalOpt.cpp

 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/GetElementPtrTypeIterator.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
 #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"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/Utils/CtorUtils.h"
 #include "llvm/Transforms/Utils/Evaluator.h"
GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
                                              GV->getType()->getAddressSpace());
   NewGV->copyAttributesFrom(GV);
   GV->getParent()->getGlobalList().insert(GV->getIterator(), NewGV);
 
   Constant *InitVal = GV->getInitializer();
   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))
+  bool EmitOneOrZero = true;
+  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)){
     IsOneZero = InitVal->isNullValue() && CI->isOne();
 
+    if (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();
+
+        // It is expected that the address of global optimized variable is on
+        // top of the stack. After optimization, value of that variable will
+        // be ether 0 for initial value or 1 for other value. The following
+        // expression should return constant integer value depending on the
+        // value at global object address:
+        // 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);
+     }
+     EmitOneOrZero = false;
+    }
+  }
+
+  if (EmitOneOrZero) {
+     // 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)) {
       // Change the store into a boolean store.
       bool StoringOther = SI->getOperand(0) == OtherVal;
       // Only do this if we weren't storing a loaded value.
       Value *StoreVal;
       if (StoringOther || SI->getOperand(0) == InitVal) {

test/Transforms/GlobalOpt/integer-bool-dwarf.ll

+;RUN: opt -S -globalopt -f %s | FileCheck %s
+
+;CHECK: !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression(DW_OP_deref, DW_OP_constu, 111, DW_OP_mul, DW_OP_constu, 0, DW_OP_plus, DW_OP_stack_value))
+
+@foo = internal global i32 0, align 4, !dbg !0
+
+; Function Attrs: noinline nounwind optnone uwtable
+define void @set1() #0 !dbg !11 {
+entry:
+  store i32 111, i32* @foo, align 4, !dbg !14
+  ret void, !dbg !15
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define void @set2() #0 !dbg !16 {
+entry:
+  store i32 0, i32* @foo, align 4, !dbg !17
+  ret void, !dbg !18
+}
+
+; Function Attrs: noinline nounwind optnone uwtable
+define i32 @get() #0 !dbg !19 {
+entry:
+  %0 = load i32, i32* @foo, align 4, !dbg !22
+  ret i32 %0, !dbg !23
+}
+
+attributes #0 = { noinline nounwind optnone uwtable }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !3, line: 1, type: !6, isLocal: true, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "integer-bool-dwarf.c", directory: "/")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{!"clang version 6.0.0 "}
+!11 = distinct !DISubprogram(name: "set1", scope: !3, file: !3, line: 3, type: !12, isLocal: false, isDefinition: true, scopeLine: 4, isOptimized: false, unit: !2, variables: !4)
+!12 = !DISubroutineType(types: !13)
+!13 = !{null}
+!14 = !DILocation(line: 5, column: 7, scope: !11)
+!15 = !DILocation(line: 6, column: 1, scope: !11)
+!16 = distinct !DISubprogram(name: "set2", scope: !3, file: !3, line: 8, type: !12, isLocal: false, isDefinition: true, scopeLine: 9, isOptimized: false, unit: !2, variables: !4)
+!17 = !DILocation(line: 10, column: 7, scope: !16)
+!18 = !DILocation(line: 11, column: 1, scope: !16)
+!19 = distinct !DISubprogram(name: "get", scope: !3, file: !3, line: 13, type: !20, isLocal: false, isDefinition: true, scopeLine: 14, isOptimized: false, unit: !2, variables: !4)
+!20 = !DISubroutineType(types: !21)
+!21 = !{!6}
+!22 = !DILocation(line: 15, column: 10, scope: !19)
+!23 = !DILocation(line: 15, column: 3, scope: !19)

test/Transforms/GlobalOpt/shrink-address-to-bool.ll

+;RUN: opt -S -globalopt -f %s | FileCheck %s
+
+;CHECK: @foo = {{.*}}, !dbg !0
+@foo = global i64 ptrtoint ([1 x i64]* @baa to i64), align 8, !dbg !0
+@baa = common global [1 x i64] zeroinitializer, align 8, !dbg !6
+
+; Function Attrs: noinline nounwind optnone uwtable
+define void @fun() #0 !dbg !16 {
+entry:
+  %0 = load i64, i64* @foo, align 8, !dbg !19
+  %1 = inttoptr i64 %0 to i64*, !dbg !19
+  %cmp = icmp ugt i64* getelementptr inbounds ([1 x i64], [1 x i64]* @baa, i32 0, i32 0), %1, !dbg !20
+  %conv = zext i1 %cmp to i32, !dbg !20
+  store i64 0, i64* @foo, align 8, !dbg !21
+  ret void, !dbg !22
+}
+
+attributes #0 = { noinline nounwind optnone uwtable }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!12, !13, !14}
+!llvm.ident = !{!15}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !3, line: 2, type: !9, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 6.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "shrink-address-to-bool.c", directory: "/")
+!4 = !{}
+!5 = !{!0, !6}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression())
+!7 = distinct !DIGlobalVariable(name: "baa", scope: !2, file: !3, line: 1, type: !8, isLocal: false, isDefinition: true)
+!8 = !DICompositeType(tag: DW_TAG_array_type, baseType: !9, size: 64, elements: !10)
+!9 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
+!10 = !{!11}
+!11 = !DISubrange(count: 1)
+!12 = !{i32 2, !"Dwarf Version", i32 4}
+!13 = !{i32 2, !"Debug Info Version", i32 3}
+!14 = !{i32 1, !"wchar_size", i32 4}
+!15 = !{!"clang version 6.0.0 "}
+!16 = distinct !DISubprogram(name: "fun", scope: !3, file: !3, line: 4, type: !17, isLocal: false, isDefinition: true, scopeLine: 4, isOptimized: false, unit: !2, variables: !4)
+!17 = !DISubroutineType(types: !18)
+!18 = !{null}
+!19 = !DILocation(line: 5, column: 9, scope: !16)
+!20 = !DILocation(line: 5, column: 7, scope: !16)
+!21 = !DILocation(line: 6, column: 7, scope: !16)
+!22 = !DILocation(line: 7, column: 1, scope: !16)