[LLVMdev] RFC: Add ISD nodes for mad (original) (raw)

Owen Anderson resistor at mac.com
Wed Jan 28 16:54:23 PST 2015

On Jan 28, 2015, at 3:47 PM, Hal Finkel <hfinkel at anl.gov> wrote:

----- Original Message ----- From: "Matt Arsenault" <Matthew.Arsenault at amd.com> To: "llvmdev at cs.uiuc.edu" <LLVMdev at cs.uiuc.edu> Sent: Wednesday, January 28, 2015 1:52:59 PM Subject: [LLVMdev] RFC: Add ISD nodes for mad

Hi, I would like to add an ISD node for an fmad operation (named either FMAD or FMULADD). It will have the semantics of returning the same result as the separate multiply and add with the intermediate rounding step, and not a differently rounded result. The motivation is to share code with the various FMA forming DAG combines, but will be generally more useful on targets that support it since it is OK to form without non-default -fp-contract modes. Why not just reuse the existing FMA node, but add an additional parameter to indicate whether enhanced intermediate precision is required?

Because that would break a lot of existing backends?

—Owen -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150128/5f0f9370/attachment.html>

More information about the llvm-dev mailing list