[cfe-commits] r78267 - in /cfe/trunk: lib/CodeGen/CGCXX.cpp test/CodeGenCXX/copy-constructor-elim.cpp
Fariborz Jahanian
fjahanian at apple.com
Wed Aug 5 18:03:10 PDT 2009
Author: fjahanian
Date: Wed Aug 5 20:02:49 2009
New Revision: 78267
URL: http://llvm.org/viewvc/llvm-project?rev=78267&view=rev
Log:
Patch to optimize away copy constructor call when
appropriate.
Added:
cfe/trunk/test/CodeGenCXX/copy-constructor-elim.cpp
Modified:
cfe/trunk/lib/CodeGen/CGCXX.cpp
Modified: cfe/trunk/lib/CodeGen/CGCXX.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGCXX.cpp?rev=78267&r1=78266&r2=78267&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGCXX.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGCXX.cpp Wed Aug 5 20:02:49 2009
@@ -255,7 +255,20 @@
cast<CXXRecordDecl>(E->getType()->getAs<RecordType>()->getDecl());
if (RD->hasTrivialConstructor())
return;
-
+
+ // Code gen optimization to eliminate copy constructor and return
+ // its first argument instead.
+ const CXXConstructorDecl *CDecl = E->getConstructor();
+ if (E->getNumArgs() == 1 &&
+ CDecl->isCopyConstructor(getContext())) {
+ CXXConstructExpr::const_arg_iterator i = E->arg_begin();
+ const Expr *SubExpr = (*i);
+ // FIXME. Any other cases can be optimized away?
+ if (isa<CallExpr>(SubExpr) || isa<CXXTemporaryObjectExpr>(SubExpr)) {
+ EmitAggExpr(SubExpr, Dest, false);
+ return;
+ }
+ }
// Call the constructor.
EmitCXXConstructorCall(E->getConstructor(), Ctor_Complete, Dest,
E->arg_begin(), E->arg_end());
Added: cfe/trunk/test/CodeGenCXX/copy-constructor-elim.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/copy-constructor-elim.cpp?rev=78267&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/copy-constructor-elim.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/copy-constructor-elim.cpp Wed Aug 5 20:02:49 2009
@@ -0,0 +1,31 @@
+// RUN: clang-cc -emit-llvm -o %t %s &&
+// RUN: grep "_ZN1CC1ERK1C" %t | count 0
+
+extern "C" int printf(...);
+
+
+struct C {
+ C() : iC(6) {printf("C()\n"); }
+ C(const C& c) { printf("C(const C& c)\n"); }
+ int iC;
+};
+
+C foo() {
+ return C();
+};
+
+class X { // ...
+public:
+ X(int) {}
+ X(const X&, int i = 1, int j = 2, C c = foo()) {
+ printf("X(const X&, %d, %d, %d)\n", i, j, c.iC);
+ }
+};
+
+int main()
+{
+ X a(1);
+ X b(a, 2);
+ X c = b;
+ X d(a, 5, 6);
+}
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