[IPSCCP] Variable not visible at Og.

llvm/include/llvm/Transforms/Utils/Local.h

@@ -461,6 +461,10 @@ void dropDebugUsers(Instruction &I);
 void hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
                               BasicBlock *BB);
 
+/// Given a constant, create a debug information expression.
+DIExpression *getExpressionForConstant(DIBuilder &DIB, const Constant &C,
+                                       Type &Ty);
+
 //===----------------------------------------------------------------------===//
 //  Intrinsic pattern matching
 //

llvm/lib/Transforms/IPO/SCCP.cpp

@@ -22,6 +22,7 @@
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/AttributeMask.h"
 #include "llvm/IR/Constants.h"
+#include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ModRef.h"
@@ -371,6 +372,18 @@ static bool runIPSCCP(
       StoreInst *SI = cast<StoreInst>(GV->user_back());
       SI->eraseFromParent();
     }
+
+    // Try to create a debug constant expression for the global variable
+    // initializer value.
+    SmallVector<DIGlobalVariableExpression *, 1> GVEs;
+    GV->getDebugInfo(GVEs);
+    if (GVEs.size() == 1) {
+      DIBuilder DIB(M);
+      if (DIExpression *InitExpr = getExpressionForConstant(
+              DIB, *GV->getInitializer(), *GV->getValueType()))
+        GVEs[0]->replaceOperandWith(1, InitExpr);
+    }
+
     MadeChanges = true;
     M.eraseGlobalVariable(GV);
     ++NumGlobalConst;

llvm/lib/Transforms/Utils/Local.cpp

@@ -3074,6 +3074,42 @@ void llvm::hoistAllInstructionsInto(BasicBlock *DomBlock, Instruction *InsertPt,
                    BB->getTerminator()->getIterator());
 }
 
+DIExpression *llvm::getExpressionForConstant(DIBuilder &DIB, const Constant &C,
+                                             Type &Ty) {
+
+  // Create integer constant expression.
+  auto createIntegerExpression = [&DIB](const Constant &CV) -> DIExpression * {
+    const APInt &API = cast<ConstantInt>(&CV)->getValue();
+    std::optional<int64_t> InitIntOpt = API.trySExtValue();
+    return InitIntOpt ? DIB.createConstantValueExpression(
+                            static_cast<uint64_t>(*InitIntOpt))
+                      : nullptr;
+  };
+
+  if (Ty.isIntegerTy())
+    return createIntegerExpression(C);
+
+  if (Ty.isFloatTy() || Ty.isDoubleTy()) {
+    const APFloat &APF = cast<ConstantFP>(&C)->getValueAPF();
+    return DIB.createConstantValueExpression(
+        APF.bitcastToAPInt().getZExtValue());
+  }
+
+  if (!Ty.isPointerTy())
+    return nullptr;
+
+  if (isa<ConstantPointerNull>(C))
+    return DIB.createConstantValueExpression(0);
+
+  if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(&C))
+    if (CE->getOpcode() == Instruction::IntToPtr) {
+      const Value *V = CE->getOperand(0);
+      if (auto CI = dyn_cast_or_null<ConstantInt>(V))
+        return createIntegerExpression(*CI);
+    }
+  return nullptr;
+}
+
 namespace {
 
 /// A potential constituent of a bitreverse or bswap expression. See

llvm/test/Transforms/SCCP/pr50901.ll

@@ -0,0 +1,154 @@
+; RUN: opt -passes=ipsccp -S -o - < %s | FileCheck %s
+
+; Global variables g_11, g_22, g_33, g_44, g_55, g_66 and g_77
+; are not visible in the debugger.
+
+;  1	int       g_1 = -4;
+;  2	float     g_2 = 4.44;
+;  3	char      g_3 = 'a';
+;  4	unsigned  g_4 = 4;
+;  5	bool      g_5 = true;
+;  6	int      *g_6 = nullptr;
+;  7	float    *g_7 = nullptr;
+;  8
+;  9	static int       g_11 = -5;
+; 10	static float     g_22 = 5.55;
+; 11	static char      g_33 = 'b';
+; 12	static unsigned  g_44 = 5;
+; 13	static bool      g_55 = true;
+; 14	static int      *g_66 = nullptr;
+; 15	static float    *g_77 = (float *)(55 + 15);
+; 16
+; 17	void bar() {
+; 18	  g_1 = g_11;
+; 19	  g_2 = g_22;
+; 20	  g_3 = g_33;
+; 21	  g_4 = g_44;
+; 22	  g_5 = g_55;
+; 23	  g_6 = g_66;
+; 24	  g_7 = g_77;
+; 25	}
+; 26
+; 27	int main() {
+; 28	  {
+; 29	    bar();
+; 30	  }
+; 31	}
+
+; CHECK: ![[G1:[0-9]+]] = !DIGlobalVariableExpression(var: ![[DBG1:[0-9]+]], expr: !DIExpression(DW_OP_constu, 18446744073709551611, DW_OP_stack_value))
+; CHECK-DAG: ![[DBG1]] = distinct !DIGlobalVariable(name: "g_11", {{.*}}
+; CHECK: ![[G2:[0-9]+]] = !DIGlobalVariableExpression(var: ![[DBG2:[0-9]+]], expr: !DIExpression(DW_OP_constu, 1085381018, DW_OP_stack_value))
+; CHECK-DAG: ![[DBG2]] = distinct !DIGlobalVariable(name: "g_22", {{.*}}
+; CHECK: ![[G3:[0-9]+]] = !DIGlobalVariableExpression(var: ![[DBG3:[0-9]+]], expr: !DIExpression(DW_OP_constu, 98, DW_OP_stack_value))
+; CHECK-DAG: ![[DBG3]] = distinct !DIGlobalVariable(name: "g_33", {{.*}}
+; CHECK: ![[G4:[0-9]+]] = !DIGlobalVariableExpression(var: ![[DBG4:[0-9]+]], expr: !DIExpression(DW_OP_constu, 5, DW_OP_stack_value))
+; CHECK-DAG: ![[DBG4]] = distinct !DIGlobalVariable(name: "g_44", {{.*}}
+; CHECK: ![[G5:[0-9]+]] = !DIGlobalVariableExpression(var: ![[DBG5:[0-9]+]], expr: !DIExpression(DW_OP_constu, 1, DW_OP_stack_value))
+; CHECK-DAG: ![[DBG5]] = distinct !DIGlobalVariable(name: "g_55", {{.*}}
+; CHECK: ![[G6:[0-9]+]] = !DIGlobalVariableExpression(var: ![[DBG6:[0-9]+]], expr: !DIExpression(DW_OP_constu, 0, DW_OP_stack_value))
+; CHECK-DAG: ![[DBG6]] = distinct !DIGlobalVariable(name: "g_66", {{.*}}
+; CHECK: ![[G7:[0-9]+]] = !DIGlobalVariableExpression(var: ![[DBG7:[0-9]+]], expr: !DIExpression(DW_OP_constu, 70, DW_OP_stack_value))
+; CHECK-DAG: ![[DBG7]] = distinct !DIGlobalVariable(name: "g_77", {{.*}}
+
+@g_1 = dso_local global i32 -4, align 4, !dbg !0
+@g_2 = dso_local global float 0x4011C28F60000000, align 4, !dbg !8
+@g_3 = dso_local global i8 97, align 1, !dbg !10
+@g_4 = dso_local global i32 4, align 4, !dbg !13
+@g_5 = dso_local global i8 1, align 1, !dbg !16
+@g_6 = dso_local global ptr null, align 8, !dbg !19
+@g_7 = dso_local global ptr null, align 8, !dbg !23
+@_ZL4g_11 = internal global i32 -5, align 4, !dbg !25
+@_ZL4g_22 = internal global float 0x4016333340000000, align 4, !dbg !27
+@_ZL4g_33 = internal global i8 98, align 1, !dbg !29
+@_ZL4g_44 = internal global i32 5, align 4, !dbg !31
+@_ZL4g_55 = internal global i8 1, align 1, !dbg !33
+@_ZL4g_66 = internal global ptr null, align 8, !dbg !35
+@_ZL4g_77 = internal global ptr inttoptr (i64 70 to ptr), align 8, !dbg !37
+
+define dso_local void @_Z3barv() !dbg !46 {
+entry:
+  %0 = load i32, ptr @_ZL4g_11, align 4, !dbg !59
+  store i32 %0, ptr @g_1, align 4, !dbg !59
+  %1 = load float, ptr @_ZL4g_22, align 4, !dbg !59
+  store float %1, ptr @g_2, align 4, !dbg !59
+  %2 = load i8, ptr @_ZL4g_33, align 1, !dbg !59
+  store i8 %2, ptr @g_3, align 1, !dbg !59
+  %3 = load i32, ptr @_ZL4g_44, align 4, !dbg !59
+  store i32 %3, ptr @g_4, align 4, !dbg !59
+  %4 = load i8, ptr @_ZL4g_55, align 1, !dbg !59
+  %tobool = trunc i8 %4 to i1, !dbg !59
+  %frombool = zext i1 %tobool to i8, !dbg !59
+  store i8 %frombool, ptr @g_5, align 1, !dbg !59
+  %5 = load ptr, ptr @_ZL4g_66, align 8, !dbg !59
+  store ptr %5, ptr @g_6, align 8, !dbg !59
+  %6 = load ptr, ptr @_ZL4g_77, align 8, !dbg !59
+  store ptr %6, ptr @g_7, align 8, !dbg !59
+  ret void, !dbg !59
+}
+
+define dso_local noundef i32 @main() !dbg !77 {
+entry:
+  call void @_Z3barv(), !dbg !80
+  ret i32 0, !dbg !82
+}
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!39, !40, !41, !42, !43, !44}
+!llvm.ident = !{!45}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "g_1", scope: !2, file: !3, line: 1, type: !22, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 18.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, retainedTypes: !4, globals: !7, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "test.cpp", directory: "")
+!4 = !{!5}
+!5 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !6, size: 64)
+!6 = !DIBasicType(name: "float", size: 32, encoding: DW_ATE_float)
+!7 = !{!0, !8, !10, !13, !16, !19, !23, !25, !27, !29, !31, !33, !35, !37}
+!8 = !DIGlobalVariableExpression(var: !9, expr: !DIExpression())
+!9 = distinct !DIGlobalVariable(name: "g_2", scope: !2, file: !3, line: 2, type: !6, isLocal: false, isDefinition: true)
+!10 = !DIGlobalVariableExpression(var: !11, expr: !DIExpression())
+!11 = distinct !DIGlobalVariable(name: "g_3", scope: !2, file: !3, line: 3, type: !12, isLocal: false, isDefinition: true)
+!12 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!13 = !DIGlobalVariableExpression(var: !14, expr: !DIExpression())
+!14 = distinct !DIGlobalVariable(name: "g_4", scope: !2, file: !3, line: 4, type: !15, isLocal: false, isDefinition: true)
+!15 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!16 = !DIGlobalVariableExpression(var: !17, expr: !DIExpression())
+!17 = distinct !DIGlobalVariable(name: "g_5", scope: !2, file: !3, line: 5, type: !18, isLocal: false, isDefinition: true)
+!18 = !DIBasicType(name: "bool", size: 8, encoding: DW_ATE_boolean)
+!19 = !DIGlobalVariableExpression(var: !20, expr: !DIExpression())
+!20 = distinct !DIGlobalVariable(name: "g_6", scope: !2, file: !3, line: 6, type: !21, isLocal: false, isDefinition: true)
+!21 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !22, size: 64)
+!22 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!23 = !DIGlobalVariableExpression(var: !24, expr: !DIExpression())
+!24 = distinct !DIGlobalVariable(name: "g_7", scope: !2, file: !3, line: 7, type: !5, isLocal: false, isDefinition: true)
+!25 = !DIGlobalVariableExpression(var: !26, expr: !DIExpression())
+!26 = distinct !DIGlobalVariable(name: "g_11", linkageName: "_ZL4g_11", scope: !2, file: !3, line: 9, type: !22, isLocal: true, isDefinition: true)
+!27 = !DIGlobalVariableExpression(var: !28, expr: !DIExpression())
+!28 = distinct !DIGlobalVariable(name: "g_22", linkageName: "_ZL4g_22", scope: !2, file: !3, line: 10, type: !6, isLocal: true, isDefinition: true)
+!29 = !DIGlobalVariableExpression(var: !30, expr: !DIExpression())
+!30 = distinct !DIGlobalVariable(name: "g_33", linkageName: "_ZL4g_33", scope: !2, file: !3, line: 11, type: !12, isLocal: true, isDefinition: true)
+!31 = !DIGlobalVariableExpression(var: !32, expr: !DIExpression())
+!32 = distinct !DIGlobalVariable(name: "g_44", linkageName: "_ZL4g_44", scope: !2, file: !3, line: 12, type: !15, isLocal: true, isDefinition: true)
+!33 = !DIGlobalVariableExpression(var: !34, expr: !DIExpression())
+!34 = distinct !DIGlobalVariable(name: "g_55", linkageName: "_ZL4g_55", scope: !2, file: !3, line: 13, type: !18, isLocal: true, isDefinition: true)
+!35 = !DIGlobalVariableExpression(var: !36, expr: !DIExpression())
+!36 = distinct !DIGlobalVariable(name: "g_66", linkageName: "_ZL4g_66", scope: !2, file: !3, line: 14, type: !21, isLocal: true, isDefinition: true)
+!37 = !DIGlobalVariableExpression(var: !38, expr: !DIExpression())
+!38 = distinct !DIGlobalVariable(name: "g_77", linkageName: "_ZL4g_77", scope: !2, file: !3, line: 15, type: !5, isLocal: true, isDefinition: true)
+!39 = !{i32 7, !"Dwarf Version", i32 5}
+!40 = !{i32 2, !"Debug Info Version", i32 3}
+!41 = !{i32 1, !"wchar_size", i32 4}
+!42 = !{i32 8, !"PIC Level", i32 2}
+!43 = !{i32 7, !"PIE Level", i32 2}
+!44 = !{i32 7, !"uwtable", i32 2}
+!45 = !{!"clang version 18.0.0"}
+!46 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !3, file: !3, line: 17, type: !47, scopeLine: 17, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2)
+!47 = !DISubroutineType(types: !48)
+!48 = !{null}
+!59 = !DILocation(line: 20, column: 9, scope: !46)
+!77 = distinct !DISubprogram(name: "main", scope: !3, file: !3, line: 27, type: !78, scopeLine: 27, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2)
+!78 = !DISubroutineType(types: !79)
+!79 = !{!22}
+!80 = !DILocation(line: 29, column: 5, scope: !81)
+!81 = distinct !DILexicalBlock(scope: !77, file: !3, line: 28, column: 3)
+!82 = !DILocation(line: 31, column: 1, scope: !77)

llvm/unittests/Transforms/Utils/LocalTest.cpp

@@ -1161,3 +1161,114 @@ TEST(Local, CanReplaceOperandWithVariable) {
 
   BB0->dropAllReferences();
 }
+
+TEST(Local, ExpressionForConstant) {
+  LLVMContext Context;
+  Module M("test_module", Context);
+  DIBuilder DIB(M);
+  DIExpression *Expr = nullptr;
+
+  auto createExpression = [&](Constant *C, Type *Ty) -> DIExpression * {
+    EXPECT_NE(C, nullptr);
+    EXPECT_NE(Ty, nullptr);
+    EXPECT_EQ(C->getType(), Ty);
+    std::unique_ptr<GlobalVariable> GV = std::make_unique<GlobalVariable>(
+        Ty, false, GlobalValue::ExternalLinkage, C, "GV");
+    EXPECT_NE(GV, nullptr);
+
+    DIExpression *Expr = getExpressionForConstant(DIB, *GV->getInitializer(),
+                                                  *GV->getValueType());
+    if (Expr) {
+      EXPECT_EQ(Expr->getNumElements(), 3u);
+      EXPECT_EQ(Expr->getElement(0), dwarf::DW_OP_constu);
+      EXPECT_EQ(Expr->getElement(2), dwarf::DW_OP_stack_value);
+    }
+    return Expr;
+  };
+
+  // Integer.
+  IntegerType *Int1Ty = Type::getInt1Ty(Context);
+  Expr = createExpression(ConstantInt::getTrue(Context), Int1Ty);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 18446744073709551615);
+
+  Expr = createExpression(ConstantInt::getFalse(Context), Int1Ty);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 0);
+
+  IntegerType *Int8Ty = Type::getInt8Ty(Context);
+  Expr = createExpression(ConstantInt::get(Int8Ty, 100), Int8Ty);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 100);
+
+  IntegerType *Int16Ty = Type::getInt16Ty(Context);
+  Expr = createExpression(ConstantInt::getSigned(Int16Ty, -50), Int16Ty);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), -50);
+
+  IntegerType *Int32Ty = Type::getInt32Ty(Context);
+  Expr = createExpression(ConstantInt::get(Int32Ty, 0x7FFFFFFF), Int32Ty);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 0x7FFFFFFF);
+
+  IntegerType *Int64Ty = Type::getInt64Ty(Context);
+  Expr =
+      createExpression(ConstantInt::get(Int64Ty, 0x7FFFFFFFFFFFFFFF), Int64Ty);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 0x7FFFFFFFFFFFFFFF);
+
+  IntegerType *Int128Ty = Type::getInt128Ty(Context);
+  Expr = createExpression(ConstantInt::get(Int128Ty, 0x7FFFFFFFFFFFFFFF),
+                          Int128Ty);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 0x7FFFFFFFFFFFFFFF);
+
+  // Float.
+  Type *FloatTy = Type::getFloatTy(Context);
+  Expr = createExpression(ConstantFP::get(FloatTy, 5.55), FloatTy);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 1085381018);
+
+  // Double.
+  Type *DoubleTy = Type::getDoubleTy(Context);
+  Expr = createExpression(ConstantFP::get(DoubleTy, -5.55), DoubleTy);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 13841306799765140275);
+
+  // Pointer.
+  PointerType *PtrTy = PointerType::get(Context, 0);
+  Expr = createExpression(ConstantPointerNull::get(PtrTy), PtrTy);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 0);
+
+  ConstantInt *K1 = ConstantInt::get(Type::getInt32Ty(Context), 1234);
+  Expr = createExpression(ConstantExpr::getIntToPtr(K1, PtrTy), PtrTy);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 1234);
+
+  ConstantInt *K2 = ConstantInt::get(Type::getInt64Ty(Context), 5678);
+  Expr = createExpression(ConstantExpr::getIntToPtr(K2, PtrTy), PtrTy);
+  EXPECT_NE(Expr, nullptr);
+  EXPECT_EQ(Expr->getElement(1), 5678);
+
+  // Others.
+  Type *HalfTy = Type::getHalfTy(Context);
+  Expr = createExpression(ConstantFP::get(HalfTy, 32), HalfTy);
+  EXPECT_EQ(Expr, nullptr);
+
+  Type *BFloatTy = Type::getBFloatTy(Context);
+  Expr = createExpression(ConstantFP::get(BFloatTy, 32), BFloatTy);
+  EXPECT_EQ(Expr, nullptr);
+
+  Type *FP128Ty = Type::getFP128Ty(Context);
+  Expr = createExpression(ConstantFP::get(FP128Ty, 32), FP128Ty);
+  EXPECT_EQ(Expr, nullptr);
+
+  Type *X86_FP80Ty = Type::getX86_FP80Ty(Context);
+  Expr = createExpression(ConstantFP::get(X86_FP80Ty, 32), X86_FP80Ty);
+  EXPECT_EQ(Expr, nullptr);
+
+  Type *PPC_FP128Ty = Type::getPPC_FP128Ty(Context);
+  Expr = createExpression(ConstantFP::get(PPC_FP128Ty, 32), PPC_FP128Ty);
+  EXPECT_EQ(Expr, nullptr);
+}