javed.absar updated this revision to Diff 89897.
javed.absar added a comment.
Hi Roger:
Thanks for the review. I have extended the test and fixed driver flag passing
that you pointed out.
Regarding the check in Sema::DeclarationIsZeroInitialized, the check if to keep
the function return value consistent, in case function is called with a
declaration that is without an initializer.
Best Regards,
Javed
https://reviews.llvm.org/D30326
Files:
include/clang/AST/APValue.h
include/clang/AST/Expr.h
include/clang/Basic/LangOptions.def
include/clang/Driver/Options.td
include/clang/Sema/Sema.h
lib/AST/APValue.cpp
lib/AST/Expr.cpp
lib/Driver/Tools.cpp
lib/Frontend/CompilerInvocation.cpp
lib/Sema/SemaDecl.cpp
test/CodeGenCXX/zi-sections.cpp
test/Driver/always-use-bss.c
Index: test/Driver/always-use-bss.c
===================================================================
--- /dev/null
+++ test/Driver/always-use-bss.c
@@ -0,0 +1,3 @@
+// RUN: %clang -### -target i686-pc-windows -fms-extensions -falways-use-bss %s 2>&1 | FileCheck %s
+// CHECK: "-falways-use-bss"
+void f() {}
Index: test/CodeGenCXX/zi-sections.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/zi-sections.cpp
@@ -0,0 +1,86 @@
+// RUN: %clang_cc1 -emit-llvm -triple i686-pc-win32 -fms-extensions -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-ZI-DATA
+// RUN: %clang_cc1 -emit-llvm -triple i686-pc-win32 -fms-extensions -falways-use-bss -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-ZI-BSS
+// Test that when '-falways-use-bss' is specified, variables initialized with zero are assigned to bss_seg.
+#pragma bss_seg(".bss.1")
+#pragma data_seg(".data.1")
+extern "C" {
+short ShortZero = 0;
+short ShortTwo = 2;
+short ShortMinusTwo = -2;
+short ShortUnInit;
+
+int IntZero = 0;
+int IntTwo = 2;
+int IntMinusTwo = -2;
+int IntUnInit;
+
+float FloatZero = 0.0;
+float FloatMinusZero = -0.0;
+float FloatTwo = 2.0;
+float FloatUnInit;
+
+double DoubleZero = 0.0;
+double DoubleMinusZero = -0.0;
+double DoubleTwo = 2.0;
+double DoubleUnInit;
+
+struct S {
+ int x, y;
+ int z;
+};
+struct S StructZero = { 0, 0, 0 };
+struct S StructTwo = { 0, 0, 2};
+struct S StructMinusTwo = {0, -2, 0};
+struct S StructUnInit;
+
+int ArrayZero[] = {0, 0, 0};
+int ArrayTwo[] = {0, 2, 0};
+int ArrayMinusTwo[] = {0, -2, 0};
+int ArrayUnInit;
+
+int ArrayWithFillerZero[10] = { 0 };
+int ArrayWithFillerTwo[10] = { 0, 2 };
+int ArrayWithAllFiller[10] = { };
+
+// CHECK-ZI-DATA: @ShortZero = global i16 0, section ".data.1", align 2
+// CHECK-ZI-BSS: @ShortZero = global i16 0, section ".bss.1", align 2
+// CHECK: @ShortTwo = global i16 2, section ".data.1", align 2
+// CHECK: @ShortMinusTwo = global i16 -2, section ".data.1", align 2
+// CHECK: @ShortUnInit = global i16 0, section ".bss.1", align 2
+//
+// CHECK-ZI-DATA: @IntZero = global i32 0, section ".data.1", align 4
+// CHECK-ZI-BSS: @IntZero = global i32 0, section ".bss.1", align 4
+// CHECK: @IntTwo = global i32 2, section ".data.1", align 4
+// CHECK: @IntMinusTwo = global i32 -2, section ".data.1", align 4
+// CHECK: @IntUnInit = global i32 0, section ".bss.1", align 4
+//
+// CHECK-ZI-DATA: @FloatZero = global float 0.000000e+00, section ".data.1", align 4
+// CHECK-ZI-BSS: @FloatZero = global float 0.000000e+00, section ".bss.1", align 4
+// CHECK: @FloatMinusZero = global float -0.000000e+00, section ".data.1", align 4
+// CHECK: @FloatTwo = global float 2.000000e+00, section ".data.1", align 4
+// CHECK: @FloatUnInit = global float 0.000000e+00, section ".bss.1", align 4
+//
+// CHECK-ZI-DATA: @DoubleZero = global double 0.000000e+00, section ".data.1", align 8
+// CHECK-ZI-BSS: @DoubleZero = global double 0.000000e+00, section ".bss.1", align 8
+// CHECK: @DoubleMinusZero = global double -0.000000e+00, section ".data.1", align 8
+// CHECK: @DoubleTwo = global double 2.000000e+00, section ".data.1", align 8
+// CHECK: @DoubleUnInit = global double 0.000000e+00, section ".bss.1", align 8
+//
+// CHECK-ZI-DATA: @StructZero = global %struct.S zeroinitializer, section ".data.1", align 4
+// CHECK-ZI-BSS: @StructZero = global %struct.S zeroinitializer, section ".bss.1", align 4
+// CHECK: @StructTwo = global %struct.S { i32 0, i32 0, i32 2 }, section ".data.1", align 4
+// CHECK: @StructMinusTwo = global %struct.S { i32 0, i32 -2, i32 0 }, section ".data.1", align 4
+// CHECK: @StructUnInit = global %struct.S zeroinitializer, section ".data.1", align 4
+//
+// CHECK-ZI-DATA: @ArrayZero = global [3 x i32] zeroinitializer, section ".data.1", align 4
+// CHECK-ZI-BSS: @ArrayZero = global [3 x i32] zeroinitializer, section ".bss.1", align 4
+// CHECK: @ArrayTwo = global [3 x i32] [i32 0, i32 2, i32 0], section ".data.1", align 4
+// CHECK: @ArrayMinusTwo = global [3 x i32] [i32 0, i32 -2, i32 0], section ".data.1", align 4
+// CHECK: @ArrayUnInit = global i32 0, section ".bss.1", align 4
+//
+// CHECK-ZI-DATA: @ArrayWithFillerZero = global [10 x i32] zeroinitializer, section ".data.1", align 4
+// CHECK-ZI-BSS: @ArrayWithFillerZero = global [10 x i32] zeroinitializer, section ".bss.1", align 4
+// CHECK: @ArrayWithFillerTwo = global [10 x i32] [i32 0, i32 2, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0], section ".data.1", align 4
+// CHECK-ZI-DATA: @ArrayWithAllFiller = global [10 x i32] zeroinitializer, section ".data.1", align 4
+// CHECK-ZI-BSS: @ArrayWithAllFiller = global [10 x i32] zeroinitializer, section ".bss.1", align 4
+}
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -10736,6 +10736,18 @@
AttrEnd.isValid() ? AttrEnd : IdentLoc);
}
+/// Check if initialization is to zero
+bool Sema::DeclarationIsZeroInitialized(VarDecl *var) {
+ Expr* InitExpr = var->getInit();
+ if (!InitExpr)
+ return var->hasGlobalStorage();
+
+ const Expr *Culprit;
+ if (!InitExpr->isConstantInitializer(Context, false, &Culprit))
+ return false;
+ return InitExpr->isZeroInitializer(Context, false, &Culprit);
+}
+
void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
if (var->isInvalidDecl()) return;
@@ -10827,7 +10839,9 @@
int SectionFlags = ASTContext::PSF_Implicit | ASTContext::PSF_Read;
if (var->getType().isConstQualified())
Stack = &ConstSegStack;
- else if (!var->getInit()) {
+ else if (!var->getInit() ||
+ (getLangOpts().AlwaysUseBSS &&
+ DeclarationIsZeroInitialized(var))) {
Stack = &BSSSegStack;
SectionFlags |= ASTContext::PSF_Write;
} else {
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -1917,6 +1917,8 @@
VT.getSubminor().getValueOr(0);
}
+ Opts.AlwaysUseBSS = Args.hasArg(OPT_falways_use_bss);
+
// Mimicing gcc's behavior, trigraphs are only enabled if -trigraphs
// is specified, or -std is set to a conforming mode.
// Trigraphs are disabled by default in c++1z onwards.
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -5935,6 +5935,10 @@
IsWindowsMSVC))
CmdArgs.push_back("-fms-extensions");
+ if (Args.hasFlag(options::OPT_falways_use_bss,
+ options::OPT_fno_always_use_bss, false))
+ CmdArgs.push_back("-falways-use-bss");
+
// -fno-use-line-directives is default.
if (Args.hasFlag(options::OPT_fuse_line_directives,
options::OPT_fno_use_line_directives, false))
Index: lib/AST/Expr.cpp
===================================================================
--- lib/AST/Expr.cpp
+++ lib/AST/Expr.cpp
@@ -2837,6 +2837,136 @@
return false;
}
+/// Returns true if the initializer is all zeros.
+bool Expr::isZeroInitializer(ASTContext &Ctx, bool IsForRef,
+ const Expr **Culprit) const {
+ if (IsForRef)
+ return false;
+
+ switch (getStmtClass()) {
+ default: break;
+ case CompoundLiteralExprClass: {
+ const Expr *Exp = cast<CompoundLiteralExpr>(this)->getInitializer();
+ return Exp->isZeroInitializer(Ctx, false, Culprit);
+ }
+ case DesignatedInitUpdateExprClass: {
+ const DesignatedInitUpdateExpr *DIUE = cast<DesignatedInitUpdateExpr>(this);
+ return DIUE->getBase()->isZeroInitializer(Ctx, false, Culprit) &&
+ DIUE->getUpdater()->isZeroInitializer(Ctx, false, Culprit);
+ }
+ case InitListExprClass: {
+ const InitListExpr *ILE = cast<InitListExpr>(this);
+ // array initializer
+ if (ILE->getType()->isArrayType()) {
+ unsigned numInits = ILE->getNumInits();
+ for (unsigned i = 0; i < numInits; i++) {
+ if (!ILE->getInit(i)->isZeroInitializer(Ctx, false, Culprit))
+ return false;
+ }
+ return true;
+ }
+
+ // record initializer
+ if (ILE->getType()->isRecordType()) {
+ unsigned ElementNo = 0;
+ RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
+ for (const auto *Field : RD->fields()) {
+ // If this is a union, skip all the fields that aren't being initialized.
+ if (RD->isUnion() && ILE->getInitializedFieldInUnion() != Field)
+ continue;
+
+ // Don't emit anonymous bitfields, they just affect layout.
+ if (Field->isUnnamedBitfield())
+ continue;
+
+ if (ElementNo < ILE->getNumInits()) {
+ const Expr *Elt = ILE->getInit(ElementNo++);
+ if (Field->isBitField()) {
+ // Bitfields have to evaluate to an integer.
+ llvm::APSInt ResultTmp;
+ if (!Elt->EvaluateAsInt(ResultTmp, Ctx)) {
+ if (Culprit)
+ *Culprit = Elt;
+ return false;
+ }
+ if (ResultTmp != 0)
+ return false;
+ } else {
+ //bool RefType = Field->getType()->isReferenceType();
+ if (!Elt->isZeroInitializer(Ctx, false, Culprit))
+ return false;
+ }
+ }
+ }
+ return true;
+ }
+ break;
+ }
+ case ImplicitValueInitExprClass:
+ case NoInitExprClass:
+ return true;
+ case ParenExprClass:
+ return cast<ParenExpr>(this)->getSubExpr()
+ ->isZeroInitializer(Ctx, false, Culprit);
+ case GenericSelectionExprClass:
+ return cast<GenericSelectionExpr>(this)->getResultExpr()
+ ->isZeroInitializer(Ctx, false, Culprit);
+ case ChooseExprClass:
+ if (cast<ChooseExpr>(this)->isConditionDependent()) {
+ if (Culprit)
+ *Culprit = this;
+ return false;
+ }
+ return cast<ChooseExpr>(this)->getChosenSubExpr()
+ ->isZeroInitializer(Ctx, false, Culprit);
+ case UnaryOperatorClass: {
+ const UnaryOperator* Exp = cast<UnaryOperator>(this);
+ if (Exp->getOpcode() == UO_Extension)
+ return Exp->getSubExpr()->isZeroInitializer(Ctx, false, Culprit);
+ break;
+ }
+ case CXXFunctionalCastExprClass:
+ case CXXStaticCastExprClass:
+ case ImplicitCastExprClass:
+ case CStyleCastExprClass:
+ case ObjCBridgedCastExprClass:
+ case CXXDynamicCastExprClass:
+ case CXXReinterpretCastExprClass:
+ case CXXConstCastExprClass: {
+ const CastExpr *CE = cast<CastExpr>(this);
+
+ if (CE->getCastKind() == CK_NoOp ||
+ CE->getCastKind() == CK_LValueToRValue ||
+ CE->getCastKind() == CK_ToUnion ||
+ CE->getCastKind() == CK_ConstructorConversion ||
+ CE->getCastKind() == CK_NonAtomicToAtomic ||
+ CE->getCastKind() == CK_AtomicToNonAtomic ||
+ CE->getCastKind() == CK_IntToOCLSampler)
+ return CE->getSubExpr()->isZeroInitializer(Ctx, false, Culprit);
+
+ break;
+ }
+ case MaterializeTemporaryExprClass:
+ return cast<MaterializeTemporaryExpr>(this)->GetTemporaryExpr()
+ ->isZeroInitializer(Ctx, false, Culprit);
+
+ case SubstNonTypeTemplateParmExprClass:
+ return cast<SubstNonTypeTemplateParmExpr>(this)->getReplacement()
+ ->isZeroInitializer(Ctx, false, Culprit);
+ case CXXDefaultArgExprClass:
+ return cast<CXXDefaultArgExpr>(this)->getExpr()
+ ->isZeroInitializer(Ctx, false, Culprit);
+ case CXXDefaultInitExprClass:
+ return cast<CXXDefaultInitExpr>(this)->getExpr()
+ ->isZeroInitializer(Ctx, false, Culprit);
+ }
+
+ EvalResult Result;
+ if (EvaluateAsRValue(Result, Ctx))
+ return Result.Val.isAllZeros();
+ return false;
+}
+
namespace {
/// \brief Look for any side effects within a Stmt.
class SideEffectFinder : public ConstEvaluatedExprVisitor<SideEffectFinder> {
Index: lib/AST/APValue.cpp
===================================================================
--- lib/AST/APValue.cpp
+++ lib/AST/APValue.cpp
@@ -656,3 +656,21 @@
MPD->resizePath(Path.size());
memcpy(MPD->getPath(), Path.data(), Path.size()*sizeof(const CXXRecordDecl*));
}
+
+bool APValue::isAllZeros() const {
+ switch (getKind()) {
+ case Uninitialized:
+ return false;
+ case Int:
+ return !getInt().getBoolValue();
+ case Float:
+ return getFloat().isPosZero();
+ case ComplexInt:
+ return !getComplexIntReal().getBoolValue() && !getComplexIntImag().getBoolValue();
+ case ComplexFloat:
+ return getComplexFloatReal().isPosZero() && getComplexFloatImag().isPosZero();
+ default:
+ return false;
+ }
+ return false;
+}
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -1763,6 +1763,7 @@
bool DeduceVariableDeclarationType(VarDecl *VDecl, bool DirectInit,
Expr *Init);
void CheckCompleteVariableDeclaration(VarDecl *VD);
+ bool DeclarationIsZeroInitialized(VarDecl *VD);
void CheckCompleteDecompositionDeclaration(DecompositionDecl *DD);
void MaybeSuggestAddingStaticToDecl(const FunctionDecl *D);
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1440,6 +1440,12 @@
def fno_data_sections : Flag <["-"], "fno-data-sections">, Group<f_Group>,
Flags<[CC1Option]>;
+def falways_use_bss : Flag<["-"], "falways-use-bss">,Group<f_Group>,
+ Flags<[CC1Option]>,
+ HelpText<"Place variables initialized to 0 in pragma bss_seg">;
+def fno_always_use_bss : Flag<["-"], "fno-always-use-bss">,Group<f_Group>,
+ Flags<[CC1Option]>;
+
def funique_section_names : Flag <["-"], "funique-section-names">,
Group<f_Group>, Flags<[CC1Option]>,
HelpText<"Use unique names for text and data sections (ELF Only)">;
Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def
+++ include/clang/Basic/LangOptions.def
@@ -179,6 +179,7 @@
ENUM_LANGOPT(DefaultCallingConv, DefaultCallingConvention, 3, DCC_None, "default calling convention")
LANGOPT(ShortEnums , 1, 0, "short enum types")
+LANGOPT(AlwaysUseBSS, 1, 0, "place variables initialized to 0 in pragma bss_seg")
LANGOPT(OpenCL , 1, 0, "OpenCL")
LANGOPT(OpenCLVersion , 32, 0, "OpenCL version")
Index: include/clang/AST/Expr.h
===================================================================
--- include/clang/AST/Expr.h
+++ include/clang/AST/Expr.h
@@ -533,6 +533,10 @@
bool isConstantInitializer(ASTContext &Ctx, bool ForRef,
const Expr **Culprit = nullptr) const;
+ /// isZeroInitializer - Returns true if this initializer is all zeros.
+ bool isZeroInitializer(ASTContext &Ctx, bool IsForRef,
+ const Expr **Culprit = nullptr) const;
+
/// EvalStatus is a struct with detailed info about an evaluation in progress.
struct EvalStatus {
/// \brief Whether the evaluated expression has side effects.
Index: include/clang/AST/APValue.h
===================================================================
--- include/clang/AST/APValue.h
+++ include/clang/AST/APValue.h
@@ -191,6 +191,7 @@
bool isUnion() const { return Kind == Union; }
bool isMemberPointer() const { return Kind == MemberPointer; }
bool isAddrLabelDiff() const { return Kind == AddrLabelDiff; }
+ bool isAllZeros() const;
void dump() const;
void dump(raw_ostream &OS) const;
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