Chris Chrulski via llvm-dev
2015-Aug-06 15:34 UTC
[llvm-dev] LibCallAliasAnalysis class instantiation parameter
Hello, Can anybody tell me the intent of the LibCallAliasAnalysisclass? I see that to instantiate it, it requires a class derived from the purevirtual class LibCallInfo, but I cannot find any classes in the source treethat derive from LibCallInfo. Is this derived class intended to be suppliedfrom a compiler front-end, library writer, or the llvm backend? I was looking at a case similar to the following: #include <math.h> double x[1000], y[1000];double angle; void rotate(int point_count) { int i; for (i=0; i < point_count; i++) { double tmp_x = x[i]; x[i] = tmp_x * cos(angle) - y[i] *sin(angle); y[i] = y[i] * cos(angle) + tmp_x *sin(angle); }} In this case, the queries done by getModRefInfo are unableto avoid loading the ‘angle’ variable from memory for each call to sin/cos.Based on the comments in LibCallSemantics.h, it appears that LibCallAliasAnalysis shouldbe able to handle this case by recognizing that sin/cos only affect errno. However, I don’t see any way of enabling this analysis without an appropriate derivation of LibCallInfo. Does anybody have info for using this analysis? Thanks, Chris -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150806/3f806e2a/attachment.html>