[llvm] r344027 - [ADT] Force the alignment of the `data` field of `IntervalMap`

[Aleksandr Urakov via llvm-commits]

Author: aleksandr.urakov
Date: Tue Oct  9 01:50:50 2018
New Revision: 344027

URL: http://llvm.org/viewvc/llvm-project?rev=344027&view=rev
Log:
[ADT] Force the alignment of the `data` field of `IntervalMap`

Summary:
This patch forces the alignment of the `data` field of `IntervalMap`.
It is because x86 MSVC doesn't apply automatically
(without `__declspec(align(...))`) alignments more than 4 bytes,
even if `alignof` has returned so. Consider the example:

https://godbolt.org/z/zIPa_G

Here `alignof` for both `S0` and `S1` returns `8`, but only `S1` is really
aligned on x86. The explanation of this behavior is here:

https://docs.microsoft.com/en-us/cpp/build/conflicts-with-the-x86-compiler

Reviewers: bkramer, stoklund, hans, rnk

Reviewed By: rnk

Subscribers: dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D52613

Modified:
    llvm/trunk/include/llvm/ADT/IntervalMap.h

Modified: llvm/trunk/include/llvm/ADT/IntervalMap.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/IntervalMap.h?rev=344027&r1=344026&r2=344027&view=diff
==============================================================================
--- llvm/trunk/include/llvm/ADT/IntervalMap.h (original)
+++ llvm/trunk/include/llvm/ADT/IntervalMap.h Tue Oct  9 01:50:50 2018
@@ -964,6 +964,7 @@ public:
 
 private:
   // The root data is either a RootLeaf or a RootBranchData instance.
+  LLVM_ALIGNAS(RootLeaf) LLVM_ALIGNAS(RootBranchData)
   AlignedCharArrayUnion<RootLeaf, RootBranchData> data;
 
   // Tree height.