[llvm] r216873 - Fix in InlineSpiller to make the rematerilization loop also consider

[Patrik Hagglund]

Author: patha
Date: Mon Sep  1 06:04:07 2014
New Revision: 216873

URL: http://llvm.org/viewvc/llvm-project?rev=216873&view=rev
Log:
Fix in InlineSpiller to make the rematerilization loop also consider
implicit uses of the whole register when a sub register is defined.

Now the same iterator is used in the rematerilization loop as in the
spill loop later.

Patch provided by Mikael Holmen.

This fix was proposed and reviewed by Quentin Colombet,
http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-August/076135.html.

Unfortunately, this error in the rematerilization code has only been
seen in a large test case for an out-of-tree target, and is probably
hard to reproduce on an in-tree target. Therefore, no testcase is
provided.

Modified:
    llvm/trunk/lib/CodeGen/InlineSpiller.cpp

Modified: llvm/trunk/lib/CodeGen/InlineSpiller.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/InlineSpiller.cpp?rev=216873&r1=216872&r2=216873&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/InlineSpiller.cpp (original)
+++ llvm/trunk/lib/CodeGen/InlineSpiller.cpp Mon Sep  1 06:04:07 2014
@@ -848,6 +848,15 @@ void InlineSpiller::markValueUsed(LiveIn
 /// reMaterializeFor - Attempt to rematerialize before MI instead of reloading.
 bool InlineSpiller::reMaterializeFor(LiveInterval &VirtReg,
                                      MachineBasicBlock::iterator MI) {
+
+  // Analyze instruction
+  SmallVector<std::pair<MachineInstr *, unsigned>, 8> Ops;
+  MIBundleOperands::VirtRegInfo RI =
+    MIBundleOperands(MI).analyzeVirtReg(VirtReg.reg, &Ops);
+
+  if (!RI.Reads)
+    return false;
+
   SlotIndex UseIdx = LIS.getInstructionIndex(MI).getRegSlot(true);
   VNInfo *ParentVNI = VirtReg.getVNInfoAt(UseIdx.getBaseIndex());
 
@@ -878,9 +887,6 @@ bool InlineSpiller::reMaterializeFor(Liv
 
   // If the instruction also writes VirtReg.reg, it had better not require the
   // same register for uses and defs.
-  SmallVector<std::pair<MachineInstr*, unsigned>, 8> Ops;
-  MIBundleOperands::VirtRegInfo RI =
-    MIBundleOperands(MI).analyzeVirtReg(VirtReg.reg, &Ops);
   if (RI.Tied) {
     markValueUsed(&VirtReg, ParentVNI);
     DEBUG(dbgs() << "\tcannot remat tied reg: " << UseIdx << '\t' << *MI);
@@ -934,10 +940,15 @@ void InlineSpiller::reMaterializeAll() {
   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++);
+    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;
+
       anyRemat |= reMaterializeFor(LI, MI);
     }
   }