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author | Pawel Wodnicki <pawel@32bitmicro.com> | 2012-12-19 09:57:57 +0000 |
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committer | Pawel Wodnicki <pawel@32bitmicro.com> | 2012-12-19 09:57:57 +0000 |
commit | 9fb60e5fee3594ec2ff43a7723d39471ee64187b (patch) | |
tree | 983e64853158bf9c8c4f9b202d336ed042260be0 | |
parent | 4696c67bb668a7083badeb63a036c69eaa8a6987 (diff) | |
download | llvm-9fb60e5fee3594ec2ff43a7723d39471ee64187b.zip llvm-9fb60e5fee3594ec2ff43a7723d39471ee64187b.tar.gz llvm-9fb60e5fee3594ec2ff43a7723d39471ee64187b.tar.bz2 |
Sync-up SROA notes
llvm-svn: 170521
-rw-r--r-- | llvm/docs/ReleaseNotes.html | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/llvm/docs/ReleaseNotes.html b/llvm/docs/ReleaseNotes.html index fbcafc3..1fc16a3 100644 --- a/llvm/docs/ReleaseNotes.html +++ b/llvm/docs/ReleaseNotes.html @@ -579,12 +579,23 @@ </p> -<p>SROA - We've re-written SROA to be significantly more powerful. -<!-- FIXME: Add more text here... --></p> +<p>SROA - We’ve re-written SROA to be significantly more powerful and generate +code which is much more friendly to the rest of the optimization pipeline. +Previously this pass had scaling problems that required it to only operate on +relatively small aggregates, and at times it would mistakenly replace a large +aggregate with a single very large integer in order to make it a scalar SSA +value. The result was a large number of i1024 and i2048 values representing any +small stack buffer. These in turn slowed down many subsequent optimization +paths.</p> +<p>The new SROA pass uses a different algorithm that allows it to only promote to +scalars the pieces of the aggregate actively in use. Because of this it doesn’t +require any thresholds. It also always deduces the scalar values from the uses +of the aggregate rather than the specific LLVM type of the aggregate. These +features combine to both optimize more code with the pass but to improve the +compile time of many functions dramatically.</p> <ul> <li>Branch weight metadata is preseved through more of the optimizer.</li> - <li>...</li> </ul> </div> |