Add the alloc_size attribute to clang, attempt 2.

This is a recommit of r290149, which was reverted in r290169 due to msan
failures. msan was failing because we were calling
`isMostDerivedAnUnsizedArray` on an invalid designator, which caused us
to read uninitialized memory. To fix this, the logic of the caller of
said function was simplified, and we now have a `!Invalid` assert in
`isMostDerivedAnUnsizedArray`, so we can catch this particular bug more
easily in the future.

Fingers crossed that this patch sticks this time. :)

Original commit message:

This patch does three things:
- Gives us the alloc_size attribute in clang, which lets us infer the
  number of bytes handed back to us by malloc/realloc/calloc/any user
  functions that act in a similar manner.
- Teaches our constexpr evaluator that evaluating some `const` variables
  is OK sometimes. This is why we have a change in
  test/SemaCXX/constant-expression-cxx11.cpp and other seemingly
  unrelated tests. Richard Smith okay'ed this idea some time ago in
  person.
- Uniques some Blocks in CodeGen, which was reviewed separately at
  D26410. Lack of uniquing only really shows up as a problem when
  combined with our new eagerness in the face of const.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@290297 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 3 deletions

diff --git a/test/CodeGenCXX/global-init.cpp b/test/CodeGenCXX/global-init.cpp
index 8144a97ce8..dc01e9096c 100644
--- a/test/CodeGenCXX/global-init.cpp
+++ b/test/CodeGenCXX/global-init.cpp
@@ -18,9 +18,6 @@ struct D { ~D(); };
 // CHECK: @__dso_handle = external global i8
 // CHECK: @c = global %struct.C zeroinitializer, align 8
 
-// It's okay if we ever implement the IR-generation optimization to remove this.
-// CHECK: @_ZN5test3L3varE = internal constant i8* getelementptr inbounds ([7 x i8], [7 x i8]* 
-
 // PR6205: The casts should not require global initializers
 // CHECK: @_ZN6PR59741cE = external global %"struct.PR5974::C"
 // CHECK: @_ZN6PR59741aE = global %"struct.PR5974::A"* getelementptr inbounds (%"struct.PR5974::C", %"struct.PR5974::C"* @_ZN6PR59741cE, i32 0, i32 0)