PNaCl: Fix ExpandCtors to handle an empty list case

PNaCl: Fix ExpandCtors to handle an empty list case

While writing a test, I noticed that ExpandCtors crashes if given the
empty list "[]", because this gets converted into an UndefValue
ConstantExpr by the LLVM assembly reader.

Fix this by checking the array's size via its type.  This replaces the
isNullValue() check.

Make error handling cleaner by splitting out a separate function.

BUG=none
TEST=test/Transforms/NaCl/expand-ctors-emptylist.ll

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-llvm.git;a=commit;h=099f6bf

[jvoung (off chromium), 2013-05-22 15:47:21]

https://codereview.chromium.org/15659005/diff/1/test/Transforms/NaCl/expand-c...
File test/Transforms/NaCl/expand-ctors-emptylist.ll (right):

https://codereview.chromium.org/15659005/diff/1/test/Transforms/NaCl/expand-c...
test/Transforms/NaCl/expand-ctors-emptylist.ll:1: ; RUN: opt %s
-nacl-expand-ctors -S | FileCheck %s -check-prefix=NO_CTORS
Why two separate RUN invocations?  Can't you just combine them?

[Mark Seaborn, 2013-05-22 16:30:38]

https://codereview.chromium.org/15659005/diff/1/test/Transforms/NaCl/expand-c...
File test/Transforms/NaCl/expand-ctors-emptylist.ll (right):

https://codereview.chromium.org/15659005/diff/1/test/Transforms/NaCl/expand-c...
test/Transforms/NaCl/expand-ctors-emptylist.ll:1: ; RUN: opt %s
-nacl-expand-ctors -S | FileCheck %s -check-prefix=NO_CTORS
On 2013/05/22 15:47:21, jvoung (cr) wrote:
> Why two separate RUN invocations?  Can't you just combine them?

It makes the test stricter.  Many other tests do this.

"CHECK-NOT: foo" only asserts that "foo" doesn't appear between the two
enclosing CHECKs within a given FileCheck invocation.  Putting the CHECK-NOTs in
their own FileCheck invocation ensures that the strings don't appear anywhere in
the output.

[jvoung (off chromium), 2013-05-22 16:50:40]

lgtm

https://codereview.chromium.org/15659005/diff/1/test/Transforms/NaCl/expand-c...
File test/Transforms/NaCl/expand-ctors-emptylist.ll (right):

https://codereview.chromium.org/15659005/diff/1/test/Transforms/NaCl/expand-c...
test/Transforms/NaCl/expand-ctors-emptylist.ll:1: ; RUN: opt %s
-nacl-expand-ctors -S | FileCheck %s -check-prefix=NO_CTORS
On 2013/05/22 16:30:38, Mark Seaborn wrote:
> On 2013/05/22 15:47:21, jvoung (cr) wrote:
> > Why two separate RUN invocations?  Can't you just combine them?
> 
> It makes the test stricter.  Many other tests do this.
> 
> "CHECK-NOT: foo" only asserts that "foo" doesn't appear between the two
> enclosing CHECKs within a given FileCheck invocation.  Putting the CHECK-NOTs
in
> their own FileCheck invocation ensures that the strings don't appear anywhere
in
> the output.

Ah, right...

[Mark Seaborn, 2013-05-22 17:09:55]

Committed patchset #1 manually as r099f6bf (presubmit successful).