[llvm-commits] [llvm-gcc-4.2] r99629 - /llvm-gcc-4.2/trunk/gcc/gimplify.c

[Chris Lattner]

Author: lattner
Date: Fri Mar 26 13:41:06 2010
New Revision: 99629

URL: http://llvm.org/viewvc/llvm-project?rev=99629&view=rev
Log:
disable a minor optimization on darwin.  For code like this:

extern int a, b, c, d;
void foo() {
  int *Arr[] = {&a, &b, &c, &d, &a, &b, &c, &d, &a, &b, &c, &d, &a, &b, &c, &d,
    &a, &b, &c, &d, &a, &b, &c, &d, &a, &b, &c, &d, &a, &b, &c, &d };
  bar(Arr);
}

the compiler synthesizes a global variable for the temporary array and then
memcpy's from it to Arr.  This is all great, but emitting the temporary global
with an L label on darwin fouls up atomization and can thus break dead code
stripping.

The right answer is to use an 'l' label without .globl, but this will require
introducing a yet-another new linkage type to llvm, which I'll do later.

This fixes rdar://7233622


Modified:
    llvm-gcc-4.2/trunk/gcc/gimplify.c

Modified: llvm-gcc-4.2/trunk/gcc/gimplify.c
URL: http://llvm.org/viewvc/llvm-project/llvm-gcc-4.2/trunk/gcc/gimplify.c?rev=99629&r1=99628&r2=99629&view=diff
==============================================================================
--- llvm-gcc-4.2/trunk/gcc/gimplify.c (original)
+++ llvm-gcc-4.2/trunk/gcc/gimplify.c Fri Mar 26 13:41:06 2010
@@ -3097,9 +3097,16 @@
 		TREE_STATIC (new) = 1;
 		TREE_READONLY (new) = 1;
                 /* LLVM LOCAL begin */
+                /* On Darwin, we can't emit temporaries like this with private
+                 * linkage, because it breaks 'atomization' of stuff in the
+                 * object file by the linker.  We need to emit this as a l label
+                 * without .globl.
+                 */
+#ifndef CONFIG_DARWIN_H
 #ifdef ENABLE_LLVM
 		DECL_LLVM_PRIVATE (new) = 1;
 #endif
+#endif
                 /* LLVM LOCAL end */
 		DECL_INITIAL (new) = ctor;
 		if (align > DECL_ALIGN (new))