Add generic __bswap[ds]i2 implementations

Summary:
In FreeBSD we needed to add generic implementations for `__bswapdi2` and
`__bswapsi2`, since gcc 6.x for mips is emitting calls to these.  See:

https://reviews.freebsd.org/D10838 and https://reviews.freebsd.org/rS318601

The actual mips code generated for these generic C versions is pretty
OK, as can be seen in the (FreeBSD) review.

I checked over gcc sources, and it seems that it can emit these calls on
more architectures, so maybe it's best to simply always add them to the
compiler-rt builtins library.

Reviewers: howard.hinnant, compnerd, petarj, emaste

Reviewed By: compnerd, emaste

Subscribers: mgorny, llvm-commits, arichardson

Differential Revision: https://reviews.llvm.org/D33516

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@303866 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 54 insertions, 2 deletions

diff --git a/lib/builtins/CMakeLists.txt b/lib/builtins/CMakeLists.txt
index 02c5b48dd..6556e7ac6 100644
--- a/lib/builtins/CMakeLists.txt
+++ b/lib/builtins/CMakeLists.txt
@@ -42,6 +42,8 @@ set(GENERIC_SOURCES
   ashlti3.c
   ashrdi3.c
   ashrti3.c
+  bswapdi2.c
+  bswapsi2.c
   clear_cache.c
   clzdi2.c
   clzsi2.c
diff --git a/lib/builtins/README.txt b/lib/builtins/README.txt
index b3d083614..e603dfa05 100644
--- a/lib/builtins/README.txt
+++ b/lib/builtins/README.txt
@@ -57,8 +57,8 @@ si_int __popcountsi2(si_int a);  // bit population
 si_int __popcountdi2(di_int a);  // bit population
 si_int __popcountti2(ti_int a);  // bit population
 
-uint32_t __bswapsi2(uint32_t a);   // a byteswapped, arm only
-uint64_t __bswapdi2(uint64_t a);   // a byteswapped, arm only
+uint32_t __bswapsi2(uint32_t a);   // a byteswapped
+uint64_t __bswapdi2(uint64_t a);   // a byteswapped
 
 // Integral arithmetic
 
diff --git a/lib/builtins/bswapdi2.c b/lib/builtins/bswapdi2.c
new file mode 100644
index 000000000..eb220007b
--- /dev/null
+++ b/lib/builtins/bswapdi2.c
@@ -0,0 +1,27 @@
+/* ===-- bswapdi2.c - Implement __bswapdi2 ---------------------------------===
+ *
+ *               The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __bswapdi2 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+
+COMPILER_RT_ABI uint64_t __bswapdi2(uint64_t u) {
+  return (
+      (((u)&0xff00000000000000ULL) >> 56) |
+      (((u)&0x00ff000000000000ULL) >> 40) |
+      (((u)&0x0000ff0000000000ULL) >> 24) |
+      (((u)&0x000000ff00000000ULL) >> 8)  |
+      (((u)&0x00000000ff000000ULL) << 8)  |
+      (((u)&0x0000000000ff0000ULL) << 24) |
+      (((u)&0x000000000000ff00ULL) << 40) |
+      (((u)&0x00000000000000ffULL) << 56));
+}
diff --git a/lib/builtins/bswapsi2.c b/lib/builtins/bswapsi2.c
new file mode 100644
index 000000000..5d941e69f
--- /dev/null
+++ b/lib/builtins/bswapsi2.c
@@ -0,0 +1,23 @@
+/* ===-- bswapsi2.c - Implement __bswapsi2 ---------------------------------===
+ *
+ *               The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __bswapsi2 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+
+COMPILER_RT_ABI uint32_t __bswapsi2(uint32_t u) {
+  return (
+      (((u)&0xff000000) >> 24) |
+      (((u)&0x00ff0000) >> 8)  |
+      (((u)&0x0000ff00) << 8)  |
+      (((u)&0x000000ff) << 24));
+}