<div dir="ltr"><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px">+    }</span><br style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px"><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px">+    else {</span><br>
<div><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px"><br></span></div><div><span style="color:rgb(0,0,0);font-family:arial,sans-serif;font-size:13px">Someone isn't using clang-format... :}</span></div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Feb 6, 2014 at 2:20 PM, Andrew Trick <span dir="ltr"><<a href="mailto:atrick@apple.com" target="_blank">atrick@apple.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: atrick<br>
Date: Thu Feb  6 13:20:41 2014<br>
New Revision: 200941<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=200941&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=200941&view=rev</a><br>
Log:<br>
Track register pressure a bit more carefully (weird corner case).<br>
<br>
This solves a problem where a def machine operand has no uses but has<br>
not been marked dead. In this case, the initial RP analysis was being<br>
extra precise and determining from LiveIntervals the the register was<br>
actually dead. This caused us to omit the register from the RP<br>
tracker's block live out. That's all good, but the per-instruction<br>
summary still accounted for it as a valid def. This could cause an<br>
assertion in the tracker later when we underflow pressure.<br>
<br>
This is from a bug report on an out-of-tree target. It is not<br>
reproducible on well-behaved targets. I'm just making an obvious fix<br>
without unit test.<br>
<br>
Modified:<br>
    llvm/trunk/lib/CodeGen/RegisterPressure.cpp<br>
<br>
Modified: llvm/trunk/lib/CodeGen/RegisterPressure.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterPressure.cpp?rev=200941&r1=200940&r2=200941&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/RegisterPressure.cpp?rev=200941&r1=200940&r2=200941&view=diff</a><br>

==============================================================================<br>
--- llvm/trunk/lib/CodeGen/RegisterPressure.cpp (original)<br>
+++ llvm/trunk/lib/CodeGen/RegisterPressure.cpp Thu Feb  6 13:20:41 2014<br>
@@ -506,7 +506,14 @@ bool RegPressureTracker::recede(SmallVec<br>
         DeadDef = LRQ.isDeadDef();<br>
       }<br>
     }<br>
-    if (!DeadDef) {<br>
+    if (DeadDef) {<br>
+      // LiveIntervals knows this is a dead even though it's MachineOperand is<br>
+      // not flagged as such. Since this register will not be recorded as<br>
+      // live-out, increase its PDiff value to avoid underflowing pressure.<br>
+      if (PDiff)<br>
+        PDiff->addPressureChange(Reg, false, MRI);<br>
+    }<br>
+    else {<br>
       if (LiveRegs.erase(Reg))<br>
         decreaseRegPressure(Reg);<br>
       else<br>
<br>
<br>
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</blockquote></div><br></div>