From: Eli Friedman <eli.friedman@gmail.com>
Date: Mon, 19 Sep 2011 23:17:44 +0000 (+0000)
Subject: Add list initialization for complex numbers in C.  Essentially, this allows "_Complex... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=0c706c29f20b6fa36759fa41333b9c3ec0bd2969;p=clang

Add list initialization for complex numbers in C.  Essentially, this allows "_Complex float x = {1.0f, 2.0f};".  See changes to docs/LanguageExtensions.html for a longer description.

<rdar://problem/9397672>.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@140090 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/docs/LanguageExtensions.html b/docs/LanguageExtensions.html
index 685544f53f..0a0ada465e 100644
--- a/docs/LanguageExtensions.html
+++ b/docs/LanguageExtensions.html
@@ -4,7 +4,7 @@
 <html>
 <head>
   <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
-  <title>Clang LanguageExtensions</title>
+  <title>Clang Language Extensions</title>
   <link type="text/css" rel="stylesheet" href="../menu.css">
   <link type="text/css" rel="stylesheet" href="../content.css">
   <style type="text/css">
@@ -85,6 +85,7 @@
   </ul>
 </li>
 <li><a href="#overloading-in-c">Function Overloading in C</a></li>
+<li><a href="#complex-list-init">Initializer lists for complex numbers in C</a></li>
 <li><a href="#builtins">Builtin Functions</a>
   <ul>
   <li><a href="#__builtin_shufflevector">__builtin_shufflevector</a></li>
@@ -895,6 +896,41 @@ caveats to this use of name mangling:</p>
 
 <p>Query for this feature with __has_extension(attribute_overloadable).</p>
 
+<!-- ======================================================================= -->
+<h2 id="complex-list-init">Initializer lists for complex numbers in C</h2>
+<!-- ======================================================================= -->
+
+<p>clang supports an extension which allows the following in C:</p>
+
+<blockquote>
+<pre>
+#include &lt;math.h&gt;
+#include &lt;complex.h&gt;
+complex float x = { 1.0f, INFINITY }; // Init to (1, Inf)
+</pre>
+</blockquote>
+
+<p>This construct is useful because there is no way to separately
+initialize the real and imaginary parts of a complex variable in
+standard C, given that clang does not support <code>_Imaginary</code>.
+(clang also supports the <code>__real__</code> and <code>__imag__</code>
+extensions from gcc, which help in some cases, but are not usable in
+static initializers.)
+
+<p>Note that this extension does not allow eliding the braces; the
+meaning of the following two lines is different:</p>
+
+<blockquote>
+<pre>
+complex float x[] = { { 1.0f, 1.0f } }; // [0] = (1, 1)
+complex float x[] = { 1.0f, 1.0f }; // [0] = (1, 0), [1] = (1, 0)
+</pre>
+</blockquote>
+
+<p>This extension also works in C++ mode, as far as that goes, but does not
+    apply to the C++ <code>std::complex</code>.  (In C++11, list
+    initialization allows the same syntax to be used with
+    <code>std::complex</code> with the same meaning.)
 
 <!-- ======================================================================= -->
 <h2 id="builtins">Builtin Functions</h2>
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 4dca86f89b..494060f221 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2617,6 +2617,9 @@ def warn_braces_around_scalar_init : Warning<
   "braces around scalar initializer">;
 def warn_many_braces_around_scalar_init : ExtWarn<
   "too many braces around scalar initializer">;
+def ext_complex_component_init : Extension<
+  "complex initialization specifying real and imaginary components "
+  "is an extension">, InGroup<DiagGroup<"complex-component-init">>;
 def err_empty_scalar_initializer : Error<"scalar initializer cannot be empty">;
 def err_illegal_initializer : Error<
   "illegal initializer (only variables can be initialized)">;
diff --git a/include/clang/Sema/Initialization.h b/include/clang/Sema/Initialization.h
index fd677ef601..d92bdae307 100644
--- a/include/clang/Sema/Initialization.h
+++ b/include/clang/Sema/Initialization.h
@@ -67,7 +67,10 @@ public:
     EK_VectorElement,
     /// \brief The entity being initialized is a field of block descriptor for
     /// the copied-in c++ object.
-    EK_BlockElement
+    EK_BlockElement,
+    /// \brief The entity being initialized is the real or imaginary part of a
+    /// complex number.
+    EK_ComplexElement
   };
   
 private:
@@ -111,8 +114,9 @@ private:
     /// virtual base.
     uintptr_t Base;
 
-    /// \brief When Kind == EK_ArrayElement or EK_VectorElement, the
-    /// index of the array or vector element being initialized. 
+    /// \brief When Kind == EK_ArrayElement, EK_VectorElement, or
+    /// EK_ComplexElement, the index of the array or vector element being
+    /// initialized. 
     unsigned Index;
   };
 
@@ -309,7 +313,8 @@ public:
   /// \brief If this is already the initializer for an array or vector
   /// element, sets the element index.
   void setElementIndex(unsigned Index) {
-    assert(getKind() == EK_ArrayElement || getKind() == EK_VectorElement);
+    assert(getKind() == EK_ArrayElement || getKind() == EK_VectorElement ||
+           EK_ComplexElement);
     this->Index = Index;
   }
 };
diff --git a/lib/CodeGen/CGExprComplex.cpp b/lib/CodeGen/CGExprComplex.cpp
index 5a752a1830..a92a7ad33e 100644
--- a/lib/CodeGen/CGExprComplex.cpp
+++ b/lib/CodeGen/CGExprComplex.cpp
@@ -738,10 +738,17 @@ ComplexPairTy ComplexExprEmitter::VisitInitListExpr(InitListExpr *E) {
     Ignore = TestAndClearIgnoreImag();
     (void)Ignore;
     assert (Ignore == false && "init list ignored");
-  if (E->getNumInits())
+
+  if (E->getNumInits() == 2) {
+    llvm::Value *Real = CGF.EmitScalarExpr(E->getInit(0));
+    llvm::Value *Imag = CGF.EmitScalarExpr(E->getInit(1));
+    return ComplexPairTy(Real, Imag);
+  } else if (E->getNumInits() == 1) {
     return Visit(E->getInit(0));
+  }
 
   // Empty init list intializes to null
+  assert(E->getNumInits() == 0 && "Unexpected number of inits");
   QualType Ty = E->getType()->getAs<ComplexType>()->getElementType();
   llvm::Type* LTy = CGF.ConvertType(Ty);
   llvm::Value* zeroConstant = llvm::Constant::getNullValue(LTy);
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index c0b7045a52..d7dfa253ad 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -742,6 +742,22 @@ public:
   }
 
   llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
+    if (ILE->getType()->isAnyComplexType() && ILE->getNumInits() == 2) {
+      // Complex type with element initializers
+      Expr *Real = ILE->getInit(0);
+      Expr *Imag = ILE->getInit(1);
+      llvm::Constant *Complex[2];
+      Complex[0] = CGM.EmitConstantExpr(Real, Real->getType(), CGF);
+      if (!Complex[0])
+        return 0;
+      Complex[1] = CGM.EmitConstantExpr(Imag, Imag->getType(), CGF);
+      if (!Complex[1])
+        return 0;
+      llvm::StructType *STy =
+          cast<llvm::StructType>(ConvertType(ILE->getType()));
+      return llvm::ConstantStruct::get(STy, Complex);
+    }
+
     if (ILE->getType()->isScalarType()) {
       // We have a scalar in braces. Just use the first element.
       if (ILE->getNumInits() > 0) {
diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 5fa8486a7f..43477b266d 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -195,6 +195,11 @@ class InitListChecker {
                            unsigned &Index,
                            InitListExpr *StructuredList,
                            unsigned &StructuredIndex);
+  void CheckComplexType(const InitializedEntity &Entity,
+                        InitListExpr *IList, QualType DeclType,
+                        unsigned &Index,
+                        InitListExpr *StructuredList,
+                        unsigned &StructuredIndex);
   void CheckScalarType(const InitializedEntity &Entity,
                        InitListExpr *IList, QualType DeclType,
                        unsigned &Index,
@@ -610,7 +615,7 @@ void InitListChecker::CheckExplicitInitList(const InitializedEntity &Entity,
     }
   }
 
-  if (T->isScalarType() && !TopLevelObject)
+  if (T->isScalarType() && IList->getNumInits() == 1 && !TopLevelObject)
     SemaRef.Diag(IList->getLocStart(), diag::warn_braces_around_scalar_init)
       << IList->getSourceRange()
       << FixItHint::CreateRemoval(IList->getLocStart())
@@ -625,7 +630,12 @@ void InitListChecker::CheckListElementTypes(const InitializedEntity &Entity,
                                             InitListExpr *StructuredList,
                                             unsigned &StructuredIndex,
                                             bool TopLevelObject) {
-  if (DeclType->isScalarType()) {
+  if (DeclType->isAnyComplexType() && SubobjectIsDesignatorContext) {
+    // Explicitly braced initializer for complex type can be real+imaginary
+    // parts.
+    CheckComplexType(Entity, IList, DeclType, Index,
+                     StructuredList, StructuredIndex);
+  } else if (DeclType->isScalarType()) {
     CheckScalarType(Entity, IList, DeclType, Index,
                     StructuredList, StructuredIndex);
   } else if (DeclType->isVectorType()) {
@@ -797,6 +807,43 @@ void InitListChecker::CheckSubElementType(const InitializedEntity &Entity,
   }
 }
 
+void InitListChecker::CheckComplexType(const InitializedEntity &Entity,
+                                       InitListExpr *IList, QualType DeclType,
+                                       unsigned &Index,
+                                       InitListExpr *StructuredList,
+                                       unsigned &StructuredIndex) {
+  assert(Index == 0 && "Index in explicit init list must be zero");
+
+  // As an extension, clang supports complex initializers, which initialize
+  // a complex number component-wise.  When an explicit initializer list for
+  // a complex number contains two two initializers, this extension kicks in:
+  // it exepcts the initializer list to contain two elements convertible to
+  // the element type of the complex type. The first element initializes
+  // the real part, and the second element intitializes the imaginary part.
+
+  if (IList->getNumInits() != 2)
+    return CheckScalarType(Entity, IList, DeclType, Index, StructuredList,
+                           StructuredIndex);
+
+  // This is an extension in C.  (The builtin _Complex type does not exist
+  // in the C++ standard.)
+  if (!SemaRef.getLangOptions().CPlusPlus)
+    SemaRef.Diag(IList->getLocStart(), diag::ext_complex_component_init)
+      << IList->getSourceRange();
+
+  // Initialize the complex number.
+  QualType elementType = DeclType->getAs<ComplexType>()->getElementType();
+  InitializedEntity ElementEntity =
+    InitializedEntity::InitializeElement(SemaRef.Context, 0, Entity);
+
+  for (unsigned i = 0; i < 2; ++i) {
+    ElementEntity.setElementIndex(Index);
+    CheckSubElementType(ElementEntity, IList, elementType, Index,
+                        StructuredList, StructuredIndex);
+  }
+}
+
+
 void InitListChecker::CheckScalarType(const InitializedEntity &Entity,
                                       InitListExpr *IList, QualType DeclType,
                                       unsigned &Index,
@@ -2060,9 +2107,14 @@ InitializedEntity::InitializedEntity(ASTContext &Context, unsigned Index,
   if (const ArrayType *AT = Context.getAsArrayType(Parent.getType())) {
     Kind = EK_ArrayElement;
     Type = AT->getElementType();
-  } else {
+  } else if (const VectorType *VT = Parent.getType()->getAs<VectorType>()) {
     Kind = EK_VectorElement;
-    Type = Parent.getType()->getAs<VectorType>()->getElementType();
+    Type = VT->getElementType();
+  } else {
+    const ComplexType *CT = Parent.getType()->getAs<ComplexType>();
+    assert(CT && "Unexpected type");
+    Kind = EK_ComplexElement;
+    Type = CT->getElementType();
   }
 }
 
@@ -2099,6 +2151,7 @@ DeclarationName InitializedEntity::getName() const {
   case EK_Delegating:
   case EK_ArrayElement:
   case EK_VectorElement:
+  case EK_ComplexElement:
   case EK_BlockElement:
     return DeclarationName();
   }
@@ -2124,6 +2177,7 @@ DeclaratorDecl *InitializedEntity::getDecl() const {
   case EK_Delegating:
   case EK_ArrayElement:
   case EK_VectorElement:
+  case EK_ComplexElement:
   case EK_BlockElement:
     return 0;
   }
@@ -2147,6 +2201,7 @@ bool InitializedEntity::allowsNRVO() const {
   case EK_Delegating:
   case EK_ArrayElement:
   case EK_VectorElement:
+  case EK_ComplexElement:
   case EK_BlockElement:
     break;
   }
@@ -2599,7 +2654,10 @@ static void TryListInitialization(Sema &S,
   //   is equivalent to
   //
   //     T x = a;
-  if (DestType->isScalarType()) {
+  if (DestType->isAnyComplexType()) {
+    // We allow more than 1 init for complex types in some cases, even though
+    // they are scalar.
+  } else if (DestType->isScalarType()) {
     if (InitList->getNumInits() > 1 && S.getLangOptions().CPlusPlus) {
       Sequence.SetFailed(InitializationSequence::FK_TooManyInitsForScalar);
       return;
@@ -3812,6 +3870,7 @@ getAssignmentAction(const InitializedEntity &Entity) {
   case InitializedEntity::EK_Member:
   case InitializedEntity::EK_ArrayElement:
   case InitializedEntity::EK_VectorElement:
+  case InitializedEntity::EK_ComplexElement:
   case InitializedEntity::EK_BlockElement:
     return Sema::AA_Initializing;
   }
@@ -3831,6 +3890,7 @@ static bool shouldBindAsTemporary(const InitializedEntity &Entity) {
   case InitializedEntity::EK_Base:
   case InitializedEntity::EK_Delegating:
   case InitializedEntity::EK_VectorElement:
+  case InitializedEntity::EK_ComplexElement:
   case InitializedEntity::EK_Exception:
   case InitializedEntity::EK_BlockElement:
     return false;
@@ -3853,6 +3913,7 @@ static bool shouldDestroyTemporary(const InitializedEntity &Entity) {
     case InitializedEntity::EK_Base:
     case InitializedEntity::EK_Delegating:
     case InitializedEntity::EK_VectorElement:
+    case InitializedEntity::EK_ComplexElement:
     case InitializedEntity::EK_BlockElement:
       return false;
 
@@ -3938,6 +3999,7 @@ static ExprResult CopyObject(Sema &S,
   case InitializedEntity::EK_Base:
   case InitializedEntity::EK_Delegating:
   case InitializedEntity::EK_VectorElement:
+  case InitializedEntity::EK_ComplexElement:
   case InitializedEntity::EK_BlockElement:
     Loc = CurInitExpr->getLocStart();
     break;
diff --git a/test/CodeGen/complex-init-list.c b/test/CodeGen/complex-init-list.c
new file mode 100644
index 0000000000..819d4f9432
--- /dev/null
+++ b/test/CodeGen/complex-init-list.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-apple-darwin10 | FileCheck %s
+
+// This file tests the clang extension which allows initializing the components
+// of a complex number individually using an initialization list.  (There is a
+// extensive description and test in test/Sema/complex-init-list.c.)
+
+_Complex float x = { 1.0f, 1.0f/0.0f };
+// CHECK: @x = global { float, float } { float 1.000000e+00, float 0x7FF0000000000000 }, align 4
+
+_Complex float f(float x, float y) { _Complex float z = { x, y }; return z; }
+// CHECK: define <2 x float> @f
+// CHECK: alloca { float, float }
\ No newline at end of file
diff --git a/test/Sema/array-init.c b/test/Sema/array-init.c
index 345ab6981b..bc958c3eea 100644
--- a/test/Sema/array-init.c
+++ b/test/Sema/array-init.c
@@ -53,7 +53,7 @@ void func() {
 
 void test() {
   int y1[3] = { 
-    { 1, 2, 3 } // expected-warning{{braces around scalar initializer}} expected-warning{{excess elements in scalar initializer}}
+    { 1, 2, 3 } // expected-warning{{excess elements in scalar initializer}}
   };
   int y3[4][3] = {  
     { 1, 3, 5 },
diff --git a/test/Sema/complex-init-list.c b/test/Sema/complex-init-list.c
new file mode 100644
index 0000000000..5b5d7ce143
--- /dev/null
+++ b/test/Sema/complex-init-list.c
@@ -0,0 +1,45 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only -pedantic
+
+// This file tests the clang extension which allows initializing the components
+// of a complex number individually using an initialization list. Basically,
+// if you have an explicit init list for a complex number that contains two
+// initializers, this extension kicks in to turn it into component-wise
+// initialization.
+//
+// This extension is useful because there isn't any way to accurately build
+// a complex number at the moment besides setting the components with
+// __real__ and __imag__, which is inconvenient and not usable for constants.
+// (Of course, there are other extensions we could implement that would
+// allow this, like some sort of __builtin_build_complex.)
+//
+// FIXME: It would be a good idea to have a warnings for implicit
+// real->complex and complex->real conversions; as-is, it's way too easy
+// to get implicit conversions when they are not intended.
+
+// Basic testcase
+_Complex float valid1 = { 1.0f, 2.0f }; // expected-warning {{specifying real and imaginary components is an extension}}
+
+
+// Struct for nesting tests
+struct teststruct { _Complex float x; };
+
+
+// Random other valid stuff
+_Complex int valid2 = { 1, 2 }; // expected-warning {{complex integer}} expected-warning {{specifying real and imaginary components is an extension}}
+struct teststruct valid3 = { { 1.0f, 2.0f} }; // expected-warning {{specifying real and imaginary components is an extension}}
+_Complex float valid4[2] = { {1.0f, 1.0f}, {1.0f, 1.0f} }; // expected-warning 2 {{specifying real and imaginary components is an extension}}
+// FIXME: We need some sort of warning for valid5
+_Complex float valid5 = {1.0f, 1.0fi}; // expected-warning {{imaginary constants}} expected-warning {{specifying real and imaginary components is an extension}}
+
+
+// Random invalid stuff
+struct teststruct invalid1 = { 1, 2 }; // expected-warning {{excess elements}}
+_Complex float invalid2 = { 1, 2, 3 }; // expected-warning {{excess elements}}
+_Complex float invalid3 = {}; // expected-error {{scalar initializer cannot be empty}} expected-warning {{GNU empty initializer}}
+
+
+// Check incomplete array sizing
+_Complex float sizetest1[] = { {1.0f, 1.0f}, {1.0f, 1.0f} }; // expected-warning 2 {{specifying real and imaginary components is an extension}}
+_Complex float sizecheck1[(sizeof(sizetest1) == sizeof(*sizetest1)*2) ? 1 : -1];
+_Complex float sizetest2[] = { 1.0f, 1.0f, {1.0f, 1.0f} };  // expected-warning {{specifying real and imaginary components is an extension}}
+_Complex float sizecheck2[(sizeof(sizetest2) == sizeof(*sizetest2)*3) ? 1 : -1];
diff --git a/test/SemaCXX/complex-init-list.cpp b/test/SemaCXX/complex-init-list.cpp
new file mode 100644
index 0000000000..e75833a37d
--- /dev/null
+++ b/test/SemaCXX/complex-init-list.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only -pedantic
+
+// This file tests the clang extension which allows initializing the components
+// of a complex number individually using an initialization list. Basically,
+// if you have an explicit init list for a complex number that contains two
+// initializers, this extension kicks in to turn it into component-wise
+// initialization.
+// 
+// See also the testcase for the C version of this extension in
+// test/Sema/complex-init-list.c.
+
+// Basic testcase
+// (No pedantic warning is necessary because _Complex is not part of C++.)
+_Complex float valid1 = { 1.0f, 2.0f };
