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DSE is really slow on this input #1795
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assigned to @lattner |
laurov@laurov-desktop:/tmp$ opt -time-passes -std-compile-opts iterative_me.bc ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- |
*** This bug has been marked as a duplicate of 930 *** |
DSE is a known issue, but this actually triggers a horrible thing in sdisel as well. Reopening for that issue. |
Further, lauro, the code looks very strange. Assuming the .c file doesn't contain hundreds of loads, can |
Fixed, patch here: This speeds up isel on this function from: ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- to: ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- a speedup of over 11x, in a release build. -Chris |
no really, patch here: |
It takes a lot of time to compile iterative_me.bc once again: ===-------------------------------------------------------------------------=== 10 dse - Number of other instrs removed ===-------------------------------------------------------------------------=== ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- |
Shark says the culprit is MemoryDependenceAnalysis.cpp:208. |
Still slow, but now GVN has joined the act: ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- |
Where does this testcase come from? IT is just a huge series of: %tmp4110778.4030 = getelementptr %struct.SnowContext* %s, i32 0, i32 9, i32 4030 ; <i8*> [#uses=2] with different offsets? Please attach a .i file. Otherwise I'll just close this as "insane". |
From the name, it looks like it's the motion estimation function for the Snow video codec, which is part of FFmpeg. |
The bitcode file doesn't parse anymore. |
Marking this as "fixed" again. I'll also upload a .ll file so that it can be reproduced if necessary. ===-------------------------------------------------------------------------=== ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name --- |
mentioned in issue llvm/llvm-bugzilla-archive#1424 |
mentioned in issue #1302 |
Extended Description
This is a very problematic function.
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