tree fba772e353c7947509e5cc3165f6d843366bfd29
parent 173573736b9b0c2be3c69848dd918fd051db5d6f
author Sanjay Patel <spatel@rotateright.com> 1411772507 +0000
committer Sanjay Patel <spatel@rotateright.com> 1411772507 +0000

Refactor reciprocal and reciprocal square root estimate into target-independent functions (part 2).

This is purely refactoring. No functional changes intended. PowerPC is the only target
that is currently using this interface.

The ultimate goal is to allow targets other than PowerPC (certainly X86 and Aarch64) to turn this:

z = y / sqrt(x)

into:

z = y * rsqrte(x)

And:

z = y / x

into:

z = y * rcpe(x)

using whatever HW magic they can use. See http://llvm.org/bugs/show_bug.cgi?id=20900 .

There is one hook in TargetLowering to get the target-specific opcode for an estimate instruction
along with the number of refinement steps needed to make the estimate usable.

Differential Revision: http://reviews.llvm.org/D5484


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218553 91177308-0d34-0410-b5e6-96231b3b80d8