Hi Susan,<div><br></div><div>Sorry - I had missed that you're using llvm-3.1, rather than the development branch. We encourage people to live on top-of-tree - it's well tested, easier for active developers to offer help with, and keeping up with incremental changes is often easier than porting between stable versions.</div>
<div><br></div><div>It also sounds like you were building a Release version of LLVM. That will not have any asserts enabled (though it will have some other diagnostics). You will probably want to work with a Debug+Asserts version (<src>/configure --disable-optimized --enable-assertions) while you're developing your allocator and watch for any asserts that trigger.</div>
<div><br></div><div>In your case the Assertion that is triggering in PEI indicates that the MachineRegisterInfo object still contained some virtregs post register-allocation. You need to call MRI->clearVirtRegs() at the end of your allocator.</div>
<div><br></div><div>Hope this helps!</div><div><br></div><div>Cheers,</div><div>Lang.<br><br><div class="gmail_quote">On Thu, Nov 1, 2012 at 2:41 PM, Susan Horwitz <span dir="ltr"><<a href="mailto:horwitz@cs.wisc.edu" target="_blank">horwitz@cs.wisc.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi again Lang,<br>
<br>
I decided to try the approach you proposed to see whether it makes the assembly-code problem go away. Again, I tried a very simple register allocator (attached) that just calls vrm.assignVirt2Phys for every vreg in each function, mapping the vreg to the first preg in the register class. I tried two versions: one maps *every* vreg, and the other only maps those for which MRI->reg_empty(vreg) returns false. In both cases I get a core dump somewhere after my reg-allocation pass has run (when I use the "tst.c" file that I sent last time as input).<br>
<br>
Note also that there is no VirtRegMap.h in the "include" directory of my installed llvm-3.1. I had to copy that file from the source directory. That seems suspicious.<br>
<br>
Any thoughts?<br>
<br>
Thanks!<br>
<br>
Susan<div class="im"><br>
<br>
On 10/31/2012 07:51 PM, Lang Hames wrote:<br>
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Susan,<br>
<br><div class="im">
I'm having trouble reproducing that error on my end, but I think the<br>
problem is probably that you're not using the VirtRegRewriter<br>
infrastructure. What your allocator needs to do is populate the virtual<br>
register mapping (VirtRegMap pass) with your allocation, rather than<br>
rewriting the registers directly through MachineRegisterInfo.<br>
<br>
Have your allocator require and preserve the VirtRegMap pass, then in<br>
your runOnMachineFunction pass grab a reference to the pass with:<br>
<br>
VirtRegMap &vrm = getAnalysis<VirtRegMap>();<br>
<br>
You can then describe your register allocations with:<br>
<br>
vrm.assignVirt2Phys(<virtreg>, <physreg>)<br>
<br>
The VirtRegRewriter pass (in VirtRegMap.cpp) will run after your<br>
allocator and apply the mapping that you described in the VirtRegMap.<br>
<br>
I hope this helps. Let me know if it doesn't fix your issue.<br>
<br>
Cheers,<br>
Lang.<br>
<br>
On Wed, Oct 31, 2012 at 3:54 PM, Susan Horwitz <<a href="mailto:horwitz@cs.wisc.edu" target="_blank">horwitz@cs.wisc.edu</a><br></div><div class="im">
<mailto:<a href="mailto:horwitz@cs.wisc.edu" target="_blank">horwitz@cs.wisc.edu</a>>> wrote:<br>
<br>
Thanks Lang!<br>
<br>
Here's another question: I'm trying to process this input:<br>
<br>
int main() {<br>
return 0;<br>
}<br>
<br>
but I'm getting an error<br></div>
Assertion `!Fn.getRegInfo(). getNumVirtRegs() && "Regalloc must<div><div class="h5"><br>
assign all vregs"' failed.<br>
<br>
At the start of runOnMachineFunction I call Fn.getRegInfo().<br>
getNumVirtRegs();<br>
and find that there is 1 virtual register. However,<br>
MRI->reg_empty(vreg)<br>
tells me that it is not used or defined. So my register-allocation<br>
code never sees it, and thus can't allocate a preg for it. I tried<br>
using MRI->replaceRegWith(vreg, preg);<br>
(where preg is available to vreg's register class) but that didn't<br>
work. When I look, the number of vregs in the function is still 1.<br>
<br>
Can you help with this?<br>
<br>
Thanks again!<br>
<br>
Susan<br>
<br>
<br>
On 10/31/2012 04:55 PM, Lang Hames wrote:<br>
<br>
Hi Susan,<br>
<br>
The meaning of "addRequired(X)" is that your pass needs X to be<br>
run, and<br>
for X to be preserved by all passes that run after X and before your<br>
pass. The PHIElemination and TwoAddressInstruction passes do not<br>
preserve each other, hence there's no way for the pass manager to<br>
schedule them for you if you addRequire(...) them.<br>
<br>
The trick is that CodeGen will schedule both of these passes to<br>
be run<br>
before _any_ register allocation pass (see Passes.cpp), so you<br>
needn't<br>
require them explicitly - you can just assume they have been<br>
run. If you<br>
just remove those lines from your getAnalysisUsage method your pass<br>
should now run as you expect.<br>
<br>
Cheers,<br>
Lang.<br>
<br>
On Wed, Oct 31, 2012 at 1:46 PM, Susan Horwitz<br>
<<a href="mailto:horwitz@cs.wisc.edu" target="_blank">horwitz@cs.wisc.edu</a> <mailto:<a href="mailto:horwitz@cs.wisc.edu" target="_blank">horwitz@cs.wisc.edu</a>><br></div></div><div><div class="h5">
<mailto:<a href="mailto:horwitz@cs.wisc.edu" target="_blank">horwitz@cs.wisc.edu</a> <mailto:<a href="mailto:horwitz@cs.wisc.edu" target="_blank">horwitz@cs.wisc.edu</a>>>> wrote:<br>
<br>
I'm trying to write a MachineFunctionPass to do register<br>
allocation.<br>
I have code that worked with an old version of LLVM. It<br>
does not<br>
work with llvm-3.1. (or various other versions that I've<br>
tried).<br>
<br>
The first problem is that including this line:<br>
<br>
AU.addRequiredID(__ TwoAddressInstructionPassID);<br>
<br>
<br>
in method getAnalysisUsage causes a runtime error:<br>
<br>
Unable to schedule 'Eliminate PHI nodes for register<br>
allocation'<br>
required by 'Unnamed pass: implement Pass::getPassName()'<br>
Unable to schedule pass<br>
UNREACHABLE executed at ...<br>
<br>
I'm invoking the pass like this (given input file foo.c):<br>
<br>
clang -emit-llvm -O0 -c foo.c -o foo.bc<br>
opt -mem2reg foo.bc > foo.ssa<br>
mv foo.ssa foo.bc<br>
llc -load Debug/lib/P4.so -regalloc=gc foo.bc<br>
<br>
<br>
I've attached my entire file (it's very short). Any help<br>
would be<br>
much appreciated!<br>
<br>
Susan Horwitz<br>
<br>
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</blockquote>
<br>
</blockquote></div><br></div>