[PATCH] D20126: [ScheduleDAG] Make sure that addVRegUseDeps is called on subreg defs

[Krzysztof Parzyszek via llvm-commits]

kparzysz created this revision.
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A follow-up to D20102:

A def operand of a virtual register can actually read a register as well. Specifically, this happens in definitions of subregisters of a virtual register (unless the "undef" flag is present). This form of a use of a register should be accounted for in the construction of the dependence graph. In ScheduleDAGInstrs::buildSchedGraph, make sure that the function addVRegUseDeps is called for such defs.


Repository:
  rL LLVM

http://reviews.llvm.org/D20126

Files:
  lib/CodeGen/ScheduleDAGInstrs.cpp

Index: lib/CodeGen/ScheduleDAGInstrs.cpp
===================================================================
--- lib/CodeGen/ScheduleDAGInstrs.cpp
+++ lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -971,15 +971,16 @@
     // Now process all uses.
     for (unsigned j = 0, n = MI->getNumOperands(); j != n; ++j) {
       const MachineOperand &MO = MI->getOperand(j);
-      if (!MO.isReg() || !MO.isUse())
+      if (!MO.isReg())
         continue;
       unsigned Reg = MO.getReg();
       if (Reg == 0)
         continue;
 
-      if (TRI->isPhysicalRegister(Reg))
-        addPhysRegDeps(SU, j);
-      else if (MO.readsReg()) // ignore undef operands
+      if (TRI->isPhysicalRegister(Reg)) {
+        if (MO.isUse())
+          addPhysRegDeps(SU, j);
+      } else if (MO.readsReg()) // ignore undef operands
         addVRegUseDeps(SU, j);
     }
 


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