[PATCH] D52613: [ADT] Change the `IntervalMap` alignment assert for x86 MSVC

[Aleksandr Urakov via Phabricator via llvm-commits]

aleksandr.urakov created this revision.
aleksandr.urakov added reviewers: Eugene.Zelenko, bkramer, stoklund.
Herald added subscribers: llvm-commits, dexonsmith.

This patch adds the different alignment assert for the x86 MSVC case. 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


Repository:
  rL LLVM

https://reviews.llvm.org/D52613

Files:
  include/llvm/ADT/IntervalMap.h


Index: include/llvm/ADT/IntervalMap.h
===================================================================
--- include/llvm/ADT/IntervalMap.h
+++ include/llvm/ADT/IntervalMap.h
@@ -1040,8 +1040,13 @@
 
 public:
   explicit IntervalMap(Allocator &a) : height(0), rootSize(0), allocator(a) {
+#if defined(_WIN32) && !defined(_WIN64)
+    assert((uintptr_t(data.buffer) & (alignof(RootLeaf) - 1) & 3) == 0 &&
+           "Insufficient alignment");
+#else
     assert((uintptr_t(data.buffer) & (alignof(RootLeaf) - 1)) == 0 &&
            "Insufficient alignment");
+#endif
     new(&rootLeaf()) RootLeaf();
   }
 


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