[PATCH] D127964: [DCE] Eliminate no-op atan and atan2 calls

[Serge Pavlov via Phabricator via llvm-commits]

sepavloff added inline comments.


================
Comment at: llvm/lib/Analysis/ConstantFolding.cpp:3189
+      case LibFunc_atanl:
+        return !Op.isDenormal();
+
----------------
Should we check for denormal argument?

C11 standard (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf, 7.12.4.3) does not mention any error condition. GLIBC documentation (https://www.gnu.org/software/libc/manual/html_node/Inverse-Trig-Functions.html) also says nothing about it.  POSIX (https://pubs.opengroup.org/onlinepubs/9699919799/functions/atan.html) says range error is optional. 

Can we safely assume `atan` never sets error?


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https://reviews.llvm.org/D127964