From 08fa65fa9c56d81d8fbdfa1eead466a9997e9600 Mon Sep 17 00:00:00 2001
From: Vladislav Vaintroub <wlad@mariadb.com>
Date: Fri, 7 Jun 2019 11:41:18 +0200
Subject: MDEV-19709 Bitmap<128>::merge etc may crash on older GCC versions

Older GCC generates SSE instruction on not-128-bit-aligned data in
Bitmap<128>::buffer

Workaround by forcing GCC not to use SSE on Bitmap<N> template.
---
 sql/sql_bitmap.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/sql/sql_bitmap.h b/sql/sql_bitmap.h
index 93c5056a8fb..4f1acb60161 100644
--- a/sql/sql_bitmap.h
+++ b/sql/sql_bitmap.h
@@ -27,6 +27,18 @@
 #include <my_bitmap.h>
 #include <my_bit.h>
 
+/*
+  Workaround GCC optimizer bug (generating SSE instuctions on unaligned data)
+*/
+#if defined (__GNUC__) && defined(__x86_64__) && (__GNUC__ < 6)
+#define NEED_GCC_NO_SSE_WORKAROUND
+#endif
+
+#ifdef NEED_GCC_NO_SSE_WORKAROUND
+#pragma GCC push_options
+#pragma GCC target ("no-sse")
+#endif
+
 template <uint width> class Bitmap
 {
   uint32 buffer[(width + 31) / 32];
@@ -266,6 +278,11 @@ public:
   };
 };
 
+#ifdef NEED_GCC_NO_SSE_WORKAROUND
+#pragma GCC pop_options
+#undef NEED_GCC_NO_SSE_WORKAROUND
+#endif
+
 /* An iterator to quickly walk over bits in ulonglong bitmap. */
 class Table_map_iterator
 {
-- 
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