<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi David,<div class=""><br class=""></div><div class="">Thanks for looking into this.</div><div class=""><br class=""></div><div class="">It seems like D68076 might not address the underlying issue here (e.g. it probably doesn't improve the situation for projects using `-g -fno-unwind-tables`?).</div><div class=""><br class=""></div><div class="">Would you mind elaborating a bit on your proposals to delay/change CFI instruction insertion? In particular, it'd help to hear a bit about how CFI instructions are inserted today (is some of it done by CFIInstrInserter, and the rest by target-specific frame lowering code?).</div><div class=""><br class=""></div><div class="">best,</div><div class="">vedant<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Sep 26, 2019, at 6:57 AM, David Tellenbach via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none; float: none; display: inline !important;" class="">Hi Paul,</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none; float: none; display: inline !important;" class="">thanks for your comments.</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">This is PR37240 (<a href="https://bugs.llvm.org/show_bug.cgi?id=37240" style="color: purple; text-decoration: underline;" class="">https://bugs.llvm.org/show_bug.cgi?id=37240</a>). I suspect this problem affects all targets; your patch D68076 would address it only for AArch64. Although I would suggest you do some careful measurements to determine the runtime performance effect, to decide whether this is acceptable.</span></blockquote><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none; float: none; display: inline !important;" class="">Yes, in principle the problem that instruction scheduling is dependent on the presence of cfi instruction should affect more targets than AArch64. However, this does not imply that all of these targets produce inconsistent assembly depending on debug information.</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><blockquote type="cite" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">The more complete approach in your steps 2 + 3 would solve this for all targets, assuming the solution did not have to be very target-specific. This would benefit the entire community.</span></blockquote><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none; float: none; display: inline !important;" class="">At least 2. would require a lot of target dependent changes because the insertion of cfi instructions would have to be moved from target specific frame lowering into an (probably again target specific) insertion pass.</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none; float: none; display: inline !important;" class=""> David</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><div class="moz-cite-prefix" style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;">On 26/09/2019 13:55,<span class="Apple-converted-space"> </span><a class="moz-txt-link-abbreviated" href="mailto:paul.robinson@sony.com" style="color: purple; text-decoration: underline;">paul.robinson@sony.com</a><span class="Apple-converted-space"> </span>wrote:<br class=""></div><blockquote type="cite" cite="mid:E3B07FDB86BFF041819DC057DEED8FEA01420BDEF8@USCULXMSG13.am.sony.com" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration: none;" class=""><div class="WordSection1" style="page: WordSection1;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">Hi David,<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">This is PR37240 (<a href="https://bugs.llvm.org/show_bug.cgi?id=37240" moz-do-not-send="true" style="color: purple; text-decoration: underline;" class="">https://bugs.llvm.org/show_bug.cgi?id=37240</a>). I suspect this problem affects all targets; your patch D68076 would address it only for AArch64. Although I would suggest you do some careful measurements to determine the runtime performance effect, to decide whether this is acceptable.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">The more complete approach in your steps 2 + 3 would solve this for all targets, assuming the solution did not have to be very target-specific. This would benefit the entire community.<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class="">--paulr<o:p class=""></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><a name="_MailEndCompose" moz-do-not-send="true" class=""><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);" class=""><o:p class=""> </o:p></span></a></div><div style="border-style: none none none solid; border-left-width: 1.5pt; border-left-color: blue; padding: 0in 0in 0in 4pt;" class=""><div class=""><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(181, 196, 223); padding: 3pt 0in 0in;" class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><b class=""><span style="font-size: 10pt; font-family: Tahoma, sans-serif;" class="">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif;" class=""><span class="Apple-converted-space"> </span>llvm-dev [<a class="moz-txt-link-freetext" href="mailto:llvm-dev-bounces@lists.llvm.org" style="color: purple; text-decoration: underline;">mailto:llvm-dev-bounces@lists.llvm.org</a>]<span class="Apple-converted-space"> </span><b class="">On Behalf Of<span class="Apple-converted-space"> </span></b>David Tellenbach via llvm-dev<br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>Thursday, September 26, 2019 5:57 AM<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>llvm-dev<br class=""><b class="">Cc:</b><span class="Apple-converted-space"> </span>nd<br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>[llvm-dev] [AArch64] Generated assembly differs depending on whether debug information is generated or not<o:p class=""></o:p></span></div></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><o:p class=""> </o:p></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">Hi,</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">we at Arm have noticed that assembly can differ when compiling for AArch64</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">depending on whether debug information is generated or not.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">The issue is reproducible for the following small example compiled with `-O1`</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">for `aarch64-arm-linux-gnu`:</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> a() {</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> b(a);</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> for (;;)</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> c("", b);</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> }</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">The reason for the difference is that AArch64 frame lowering emits CFI</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">instructions if debug information is enabled but not if not. CFI instructions</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">act as scheduling boundaries during instruction scheduling and therefore lead to</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">differing scheduling regions and an overall different instruction scheduling.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">We see several ways to fix the issue and would welcome comments on this:</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> 1. Enabling unwind tables by default for AArch64: By enabling unwind tables</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> by default CFI instructions will be inserted in both, debug and non-debug</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> mode. This should lead to smaller scheduling regions and probably to less</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> scheduling potential.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> However, I've measured the average size of scheduling regions for randomly</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> generated programs with and without default unwind tables and found an</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> average difference of 0.5 to 1 instruction. Other architectures such as x86</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> do exactly this and therefore don't face the issue.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> The following patch on Phabricator introduces the said change:</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> <span class="Apple-converted-space"> </span><a class="moz-txt-link-freetext" href="https://reviews.llvm.org/D68076" style="color: purple; text-decoration: underline;">https://reviews.llvm.org/D68076</a></span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> 2. Postpone insertion of CFI instructions until after instruction scheduling.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> This would require a new pass running after instruction scheduling that </span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> inserts CFI instructions if needed. The downside I see is increased</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> compile-time and probably some code duplication with frame lowering.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> 3. Change instruction scheduling such that CFI instructions get tied together</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> with relevant instructions in such a way that they get scheduled together.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> If this could work it would probably the cleanest solution.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">To summarize:</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">1. would make scheduling in the non-debug case behave like in the</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">debug case and therefore probably cost some scheduling potential. However, it</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">would be by far the most easy to implement. 2. + 3. would probably lead to</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">better scheduling but seem to be more complex to implement.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class="">Comments and additional ideas are welcome.</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div><div class=""><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span class=""> David</span><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""></o:p></span></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman", serif;" class=""><span style="font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></span></div></div></div></div></blockquote><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; 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