Don't hoist or sink instructions with physreg uses if the physreg is

allocatable. Even if it doesn't appear to have any defs, it may latter
on after register allocation.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82834 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 3 deletions

diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 8123d99..61678f1 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -44,6 +44,7 @@ namespace {
     const TargetMachine   *TM;
     const TargetInstrInfo *TII;
     const TargetRegisterInfo *TRI;
+    BitVector AllocatableSet;
 
     // Various analyses that we use...
     MachineLoopInfo      *LI;      // Current MachineLoopInfo
@@ -138,6 +139,7 @@ bool MachineLICM::runOnMachineFunction(MachineFunction &MF) {
   TII = TM->getInstrInfo();
   TRI = TM->getRegisterInfo();
   RegInfo = &MF.getRegInfo();
+  AllocatableSet = TRI->getAllocatableSet(MF);
 
   // Get our Loop information...
   LI = &getAnalysis<MachineLoopInfo>();
@@ -261,13 +263,20 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) {
       // we can move it, but only if the def is dead.
       if (MO.isUse()) {
         // If the physreg has no defs anywhere, it's just an ambient register
-        // and we can freely move its uses.
+        // and we can freely move its uses. Alternatively, if it's allocatable,
+        // it could get allocated to something with a def during allocation.
         if (!RegInfo->def_empty(Reg))
           return false;
+        if (AllocatableSet.test(Reg))
+          return false;
         // Check for a def among the register's aliases too.
-        for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias)
-          if (!RegInfo->def_empty(*Alias))
+        for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
+          unsigned AliasReg = *Alias;
+          if (!RegInfo->def_empty(AliasReg))
+            return false;
+          if (AllocatableSet.test(AliasReg))
             return false;
+        }
         // Otherwise it's safe to move.
         continue;
       } else if (!MO.isDead()) {