<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"><base href="x-msg://1256/"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Mei,<div><br></div><div>I have concerns about the general approach. It's not clear to me this kind of transformation is generally a win on all modern architectures. As an example from your code:</div><div><br></div><div><div>+/// Before:</div><div>+/// ......</div><div>+/// %cmp10 = fcmp une float %tmp1, %tmp2</div><div>+/// br i1 %cmp1, label %if.then, label %lor.rhs</div><div>+///</div><div>+/// lor.rhs:</div><div>+/// ......</div><div>+/// %cmp11 = fcmp une float %tmp3, %tmp4</div><div>+/// br i1 %cmp11, label %if.then, label %ifend</div><div>+///</div><div>+/// if.end: // the merge block</div><div>+/// ......</div><div>+///</div><div>+/// if.then: // has two predecessors, both of them contains conditional branch.</div><div>+/// ......</div><div>+/// br label %if.end;</div><div>+///</div><div>+/// After:</div><div>+/// ......</div><div>+/// %cmp10 = fcmp une float %tmp1, %tmp2</div><div>+/// ......</div><div>+/// %cmp11 = fcmp une float %tmp3, %tmp4</div><div>+/// %cmp12 = or i1 %cmp10, %cmp11 // parallel-or mode.</div><div>+/// br i1 %cmp12, label %if.then, label %ifend</div><div>+///</div><div>+/// if.end:</div><div>+/// ......</div><div>+/// </div><div>+/// if.then:</div><div>+/// ......</div><div>+/// br label %if.end;</div><div><br></div><div>The pre-transformed code is probably going to run faster than the transformed code on a modern Intel x86 processor. On ARM processors, saving the value of conditional registers and or'ing them is probably also quite expensive. I also suspect the transformation will prohibit the target from some if-conversion opportunities.</div><div><br></div><div>Have you thought about having targets providing cost information to the pass? Alternatively this may be done as a codegen pass?</div><div><br></div><div>Evan</div><div><br></div><div><br></div><div><div>On Jun 20, 2013, at 4:26 PM, "Ye, Mei" <<a href="mailto:Mei.Ye@amd.com">Mei.Ye@amd.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div lang="EN-US" link="blue" vlink="purple" style="font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div class="WordSection1" style="page: WordSection1; "><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Hi Sean<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">See the attached new patch, which fixes all issues brought up by you.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">I ran “clang-format” on whole files which makes more diffs. Hopefully this is OK with you.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">It will be nice if the check-in process can automatically run “clang-format”.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">-Mei<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span></div><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(181, 196, 223); padding: 3pt 0in 0in; "><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; ">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif; "><span class="Apple-converted-space"> </span>Sean Silva [mailto:silvas@<a href="http://purdue.edu" style="color: purple; text-decoration: underline; ">purdue.edu</a>]<span class="Apple-converted-space"> </span><br><b>Sent:</b><span class="Apple-converted-space"> </span>Tuesday, June 18, 2013 4:48 PM<br><b>To:</b><span class="Apple-converted-space"> </span>Ye, Mei<br><b>Cc:</b><span class="Apple-converted-space"> </span><a href="mailto:llvm-commits@cs.uiuc.edu" style="color: purple; text-decoration: underline; ">llvm-commits@cs.uiuc.edu</a><br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: submit [PATCH] SimplifyCFG for code review<o:p></o:p></span></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div><div><p class="MsoNormal" style="margin: 0in 0in 12pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></p><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">On Tue, Jun 18, 2013 at 4:27 PM, Ye, Mei <<a href="mailto:Mei.Ye@amd.com" target="_blank" style="color: purple; text-decoration: underline; ">Mei.Ye@amd.com</a>> wrote:<o:p></o:p></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">Hi Sean</span><o:p></o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); "> </span><o:p></o:p></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125); ">There are some considerations that go into this test sample to create an opportunity for the transformation.</span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">The test case should run *only* the simplifycfg pass (I see now that you have `-O3` in your test case; please remove `-O3`). You can probably just write a simple .ll function with IR that looks like the "Before" case in your documentation comment. <o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Also,<o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">+; RUN: opt < %s -O3 -simplifycfg -S | grep br | count 2<o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">+%struct.float2_tag = type { float, float }<o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Please use FileCheck for all new tests. Using grep is deprecated.<o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">-- Sean Silva<o:p></o:p></div></div></div></div></div></div><span><odc_simplifycfg></span>_______________________________________________<br>llvm-commits mailing list<br><a href="mailto:llvm-commits@cs.uiuc.edu" style="color: purple; text-decoration: underline; ">llvm-commits@cs.uiuc.edu</a><br><a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits" style="color: purple; text-decoration: underline; ">http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits</a></div></blockquote></div><br></div></body></html>