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| author | Eli Friedman <eli.friedman@gmail.com> | 2011-03-22 20:49:53 +0000 |
|---|---|---|
| committer | Eli Friedman <eli.friedman@gmail.com> | 2011-03-22 20:49:53 +0000 |
| commit | 97ab5803df4a549db9cd93e80426971e64562672 (patch) | |
| tree | cf97f753b7556a4f5eca23e395cc2f24d0dacf1c /lib/Target/README.txt | |
| parent | 83cf2ffdcd5c555bbdaf440a76cf90cfd5a1ce87 (diff) | |
| download | llvm-97ab5803df4a549db9cd93e80426971e64562672.tar.gz llvm-97ab5803df4a549db9cd93e80426971e64562672.tar.bz2 llvm-97ab5803df4a549db9cd93e80426971e64562672.tar.xz | |
A bit more analysis of a memset-related README entry.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128107 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Target/README.txt')
| -rw-r--r-- | lib/Target/README.txt | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 63f1f79962..33941f451a 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -2074,11 +2074,12 @@ for.end: ; preds = %entry } This shouldn't need the ((zext (%n - 1)) + 1) game, and it should ideally fold -the two memset's together. The issue with %n seems to stem from poor handling -of the original loop. +the two memset's together. -To simplify this, we need SCEV to know that "n != 0" because of the dominating -conditional. That would turn the second memset into a simple memset of 'n'. +The issue with the addition only occurs in 64-bit mode, and appears to be at +least partially caused by Scalar Evolution not keeping its cache updated: it +returns the "wrong" result immediately after indvars runs, but figures out the +expected result if it is run from scratch on IR resulting from running indvars. //===---------------------------------------------------------------------===// |