Add the alloc_size attribute to clang.

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.

Differential Revision: https://reviews.llvm.org/D14274

llvm-svn: 290149

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 02cbdf0c9e8..9b96a59aec3 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -1683,6 +1683,14 @@ void CodeGenModule::ConstructAttributeList(
 
     HasAnyX86InterruptAttr = TargetDecl->hasAttr<AnyX86InterruptAttr>();
     HasOptnone = TargetDecl->hasAttr<OptimizeNoneAttr>();
+    if (auto *AllocSize = TargetDecl->getAttr<AllocSizeAttr>()) {
+      Optional<unsigned> NumElemsParam;
+      // alloc_size args are base-1, 0 means not present.
+      if (unsigned N = AllocSize->getNumElemsParam())
+        NumElemsParam = N - 1;
+      FuncAttrs.addAllocSizeAttr(AllocSize->getElemSizeParam() - 1,
+                                 NumElemsParam);
+    }
   }
 
   // OptimizeNoneAttr takes precedence over -Os or -Oz. No warning needed.