<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Aug 12, 2015, at 8:36 PM, Dylan McKay <<a href="mailto:dylanmckay34@gmail.com" class="">dylanmckay34@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><ul style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; margin: 1.2em 0px; padding-left: 2em;" class=""><li style="margin: 0.5em 0px;" class="">16-bit addition is illegal, should expand into an add and an add with carry</li><li style="margin: 0.5em 0px;" class="">A few operations support 16-bit operands - the 16-bit<span class="Apple-converted-space"> </span><code style="font-size: 0.85em; font-family: Consolas, Inconsolata, Courier, monospace; margin: 0px 0.15em; padding: 0px 0.3em; white-space: pre-wrap; border: 1px solid rgb(234, 234, 234); border-top-left-radius: 3px; border-top-right-radius: 3px; border-bottom-right-radius: 3px; border-bottom-left-radius: 3px; display: inline; background-color: rgb(248, 248, 248);" class="">DREGS</code><span class="Apple-converted-space"> </span>register class</li></ul></div></blockquote></div>This sounds like basically the same situation AMDGPU has with 64-bit integers. Since you have a 16-bit register class, you avoid terrible problems by not having i16 be a legal type. There is no 64-bit add, and needs to be expanded into 32-bit add + carry. There are fewer 64-bit operations available, but some are. It’s faked by saying 64-bit add is legal and the expand to add + carry is handled during instruction selection, which works and also makes addressing mode matching easier.<div class=""><br class=""></div><div class=""><br class=""></div></body></html>