Add target hook CodeGen queries when generating builtin pow*.

Without fmath-errno, Clang currently generates calls to @llvm.pow.* intrinsics
when it sees pow*(). This may not be suitable for all targets (for
example le32/PNaCl), so the attached patch adds a target hook that CodeGen
queries. The target can state its preference for having or not having the
intrinsic generated. Non-PNaCl behavior remains unchanged;
PNaCl-specific test added.




git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185568 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TargetInfo.h b/lib/CodeGen/TargetInfo.h
index a7fb886..1be7f4d 100644
--- a/lib/CodeGen/TargetInfo.h
+++ b/lib/CodeGen/TargetInfo.h
@@ -74,6 +74,10 @@
     ///     through such registers.
     virtual bool extendPointerWithSExt() const { return false; }
 
+    /// Controls whether BIpow* emit an intrinsic call instead of a library
+    /// function call.
+    virtual bool emitIntrinsicForPow() const { return true; }
+
     /// Determines the DWARF register number for the stack pointer, for
     /// exception-handling purposes.  Implements __builtin_dwarf_sp_column.
     ///