Fix r141744.

1. The speculation check may not have been performed if the BB hasn't had a load
   LICM candidate.
2. If the candidate would be CSE'ed, then go ahead and speculatively LICM the
   instruction even if it's in high register pressure situation.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141747 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 1 deletions

diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 63c73d2e4e..6116281d59 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -251,6 +251,10 @@ namespace {
     bool EliminateCSE(MachineInstr *MI,
            DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator &CI);
 
+    /// MayCSE - Return true if the given instruction will be CSE'd if it's
+    /// hoisted out of the loop.
+    bool MayCSE(MachineInstr *MI);
+
     /// Hoist - When an instruction is found to only use loop invariant operands
     /// that is safe to hoist, this instruction is called to do the dirty work.
     /// It returns true if the instruction is hoisted.
@@ -1047,7 +1051,7 @@ bool MachineLICM::IsProfitableToHoist(MachineInstr &MI) {
     // Also, do not "speculate" in high register pressure situation. If an
     // instruction is not guaranteed to be executed in the loop, it's best to be
     // conservative.
-    if (SpeculationState == SpeculateTrue ||
+    if ((!IsGuaranteedToExecute(MI.getParent()) && !MayCSE(&MI)) ||
         (!TII->isTriviallyReMaterializable(&MI, AA) &&
          !MI.isInvariantLoad(AA)))
       return false;
@@ -1183,6 +1187,20 @@ bool MachineLICM::EliminateCSE(MachineInstr *MI,
   return false;
 }
 
+/// MayCSE - Return true if the given instruction will be CSE'd if it's
+/// hoisted out of the loop.
+bool MachineLICM::MayCSE(MachineInstr *MI) {
+  unsigned Opcode = MI->getOpcode();
+  DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator
+    CI = CSEMap.find(Opcode);
+  // Do not CSE implicit_def so ProcessImplicitDefs can properly propagate
+  // the undef property onto uses.
+  if (CI == CSEMap.end() || MI->isImplicitDef())
+    return false;
+
+  return LookForDuplicate(MI, CI->second) != 0;
+}
+
 /// Hoist - When an instruction is found to use only loop invariant operands
 /// that are safe to hoist, this instruction is called to do the dirty work.
 ///