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| author | Andrea Di Biagio <Andrea_DiBiagio@sn.scee.net> | 2015-01-06 17:41:18 +0000 |
|---|---|---|
| committer | Andrea Di Biagio <Andrea_DiBiagio@sn.scee.net> | 2015-01-06 17:41:18 +0000 |
| commit | f807a6f2970398b85ccd2a3ba6d8959426a9872f (patch) | |
| tree | 911eb76a03413e1686ee193038b3d84907aef6a6 /llvm/lib/Support/regutils.h | |
| parent | a76dfbd4288271d3a61fe2f4307c406780ce7c49 (diff) | |
| download | bcm5719-llvm-f807a6f2970398b85ccd2a3ba6d8959426a9872f.tar.gz bcm5719-llvm-f807a6f2970398b85ccd2a3ba6d8959426a9872f.zip | |
[CodeGenPrepare] Improved logic to speculate calls to cttz/ctlz.
This patch improves the logic added at revision 224899 (see review D6728) that
teaches the backend when it is profitable to speculate calls to cttz/ctlz.
The original algorithm conservatively avoided speculating more than one
instruction from a basic block in a control flow grap modelling an if-statement.
In particular, the only allowed instruction (excluding the terminator) was a
call to cttz/ctlz. However, there are cases where we could be less conservative
and still be able to speculate a call to cttz/ctlz.
With this patch, CodeGenPrepare now tries to speculate a cttz/ctlz if the
result is zero extended/truncated in the same basic block, and the zext/trunc
instruction is "free" for the target.
Added new test cases to CodeGen/X86/cttz-ctlz.ll
Differential Revision: http://reviews.llvm.org/D6853
llvm-svn: 225274
Diffstat (limited to 'llvm/lib/Support/regutils.h')
0 files changed, 0 insertions, 0 deletions
