Author: hans
Date: Thu Aug 29 06:03:14 2019
New Revision: 370352
URL: http://llvm.org/viewvc/llvm-project?rev=370352&view=rev
Log:
ReleaseNotes: matching wide stores (r362472)
Modified:
llvm/branches/release_90/docs/ReleaseNotes.rst
Modified: llvm/branches/release_90/docs/ReleaseNotes.rst
URL:
http://llvm.org/viewvc/llvm-project/llvm/branches/release_90/docs/ReleaseNotes.rst?rev=370352&r1=370351&r2=370352&view=diff
==============================================================================
--- llvm/branches/release_90/docs/ReleaseNotes.rst (original)
+++ llvm/branches/release_90/docs/ReleaseNotes.rst Thu Aug 29 06:03:14 2019
@@ -85,6 +85,30 @@ Noteworthy optimizations
`bug 42763 <https://bugs.llvm.org/show_bug.cgi?id=42763>_` and
`post commit discussion
<http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190422/646945.html>_`.
+* LLVM will now pattern match wide scalar values stored by a succession of
+ narrow stores. For example, Clang will compile the following function that
+ writes a 32-bit value in big-endian order in a portable manner:
+
+ .. code-block:: c
+
+ void write32be(unsigned char *dst, uint32_t x) {
+ dst[0] = x >> 24;
+ dst[1] = x >> 16;
+ dst[2] = x >> 8;
+ dst[3] = x >> 0;
+ }
+
+ into the x86_64 code below:
+
+ .. code-block:: asm
+
+ write32be:
+ bswap esi
+ mov dword ptr [rdi], esi
+ ret
+
+ (The corresponding read patterns have been matched since LLVM 5.)
+
* LLVM will now omit range checks for jump tables when lowering switches with
unreachable default destination. For example, the switch dispatch in the C++
code below
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