In the following function, each initializer element is expanded into a
getelementptr/store pair, resulting in a TON of code.  This is a reduced &
simplified testcase from imagemagick, whose giant array is not nearly as
pointless as this one.

----
int test(int x) {
  const int array[] = {
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
     17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 17, 23, 123, 123, 49, 
   };
   return array[x];
} 
----

When the array has more than a few initializers, we should memcpy from a
statically initalized global variable into the array alloca.  Ideally we should
then be able to eliminate the alloca (in this case where the array is never
written to besides the memcpy), but that's an optimization, not a "cannot
compile the testcase because the compiler runs forever" bug.

-Chris

Note to self:  This bug can be fixed in llvm_expand_constructor.  We should
handle the following cases:

* All constant values - Statically initialize a global, and memcpy from it
* Mostly zero values - Initialize with memset, then store nonzero elements into it
* Mostly constant values - Statically initialize a global with the constant
  parts, memcpy from it, then clobber the non-constant parts.

Tommorow.

-Chris

Related to this bug, we currently compile things like this:

int foo() {
  int t[1025] = { 1024 };
}

Into a loop to zero initialize t.  It would be better to use memset when possible.

-Chris

The really bad incarnations of this bug are now fixed.  Patch here:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20040308/012934.html

Testcase here:
test/Regression/CFrontend/2004-03-09-LargeArrayInitializers.c

I will file a new bug for the more esoteric bad cases that we still fail, which
are blocked on the rewrite of the CFE initializer code.

-Chris