[LLVMdev] Help with definition of subregisters; spill, rematerialization and implicit uses

[Mikael Holmén]

Hi Quentin,

On 08/23/14 01:43, Quentin Colombet wrote:
 > [...]
>
> Alternative we could do the same thing as insertReload:
> Walk all uses *and* defs and apply the rematerialization for each use or readsRegs.
> Notice the different iterator for remat and for reload. They should be the same.

Excellent! Ok so now I did

@@ -932,15 +932,28 @@ void InlineSpiller::reMaterializeAll() {
    // Try to remat before all uses of snippets.
    bool anyRemat = false;
    for (unsigned i = 0, e = RegsToSpill.size(); i != e; ++i) {
      unsigned Reg = RegsToSpill[i];
      LiveInterval &LI = LIS.getInterval(Reg);
-    for (MachineRegisterInfo::use_bundle_nodbg_iterator
-         RI = MRI.use_bundle_nodbg_begin(Reg), E = 
MRI.use_bundle_nodbg_end();
-         RI != E; ) {
-      MachineInstr *MI = &*(RI++);
-      anyRemat |= reMaterializeFor(LI, MI);
+
+    for (MachineRegisterInfo::reg_bundle_iterator
+           RegI = MRI.reg_bundle_begin(Reg), E = MRI.reg_bundle_end();
+         RegI != E; ) {
+      MachineInstr *MI = &*(RegI++);
+
+      // Debug values are not allowed to affect codegen.
+      if (MI->isDebugValue()) {
+        continue;
+      }
+
+      // Analyze instruction.
+      SmallVector<std::pair<MachineInstr*, unsigned>, 8> Ops;
+      MIBundleOperands::VirtRegInfo RI =
+        MIBundleOperands(MI).analyzeVirtReg(Reg, &Ops);
+
+      if (RI.Reads)
+        anyRemat |= reMaterializeFor(LI, MI);
      }
    }
    if (!anyRemat)
      return;

So with this change InlineSpiller::reMaterializeAll is more similar to 
InlineSpiller::spillAroundUses, and now I'm not aware of any crashes 
anymore. :) My test case works, and I haven't seen any other tests 
suddenly failing.

Is this a good change that should be done not only locally in my version?

Thanks alot for your help!
/Mikael

>
> I let you give it a try.
>
> Thanks,
> -Quentin
>>
>> Thanks,
>> Mikael
>
>
>