[llvm-commits] [llvm] r122133 - in /llvm/trunk/lib/CodeGen: InlineSpiller.cpp LiveRangeEdit.h

[Jakob Stoklund Olesen]

Author: stoklund
Date: Fri Dec 17 21:04:14 2010
New Revision: 122133

URL: http://llvm.org/viewvc/llvm-project?rev=122133&view=rev
Log:
Teach the inline spiller to attempt folding a load instruction into its single
use before rematerializing the load.

This allows us to produce:

    addps	LCPI0_1(%rip), %xmm2

Instead of:

    movaps	LCPI0_1(%rip), %xmm3
    addps	%xmm3, %xmm2

Saving a register and an instruction. The standard spiller already knows how to
do this.

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

Modified: llvm/trunk/lib/CodeGen/InlineSpiller.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/InlineSpiller.cpp?rev=122133&r1=122132&r2=122133&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/InlineSpiller.cpp (original)
+++ llvm/trunk/lib/CodeGen/InlineSpiller.cpp Fri Dec 17 21:04:14 2010
@@ -85,7 +85,8 @@
 
   bool coalesceStackAccess(MachineInstr *MI);
   bool foldMemoryOperand(MachineBasicBlock::iterator MI,
-                         const SmallVectorImpl<unsigned> &Ops);
+                         const SmallVectorImpl<unsigned> &Ops,
+                         MachineInstr *LoadMI = 0);
   void insertReload(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
   void insertSpill(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
 };
@@ -141,6 +142,14 @@
     }
   }
 
+  // Before rematerializing into a register for a single instruction, try to
+  // fold a load into the instruction. That avoids allocating a new register.
+  if (RM.OrigMI->getDesc().canFoldAsLoad() &&
+      foldMemoryOperand(MI, Ops, RM.OrigMI)) {
+    edit_->markRematerialized(RM.ParentVNI);
+    return true;
+  }
+
   // Alocate a new register for the remat.
   LiveInterval &NewLI = edit_->create(mri_, lis_, vrm_);
   NewLI.markNotSpillable();
@@ -243,9 +252,13 @@
 }
 
 /// foldMemoryOperand - Try folding stack slot references in Ops into MI.
-/// Return true on success, and MI will be erased.
+/// @param MI     Instruction using or defining the current register.
+/// @param Ops    Operandices from readsWritesVirtualRegister().
+/// @param LoadMI Load instruction to use instead of stack slot when non-null.
+/// @return       True on success, and MI will be erased.
 bool InlineSpiller::foldMemoryOperand(MachineBasicBlock::iterator MI,
-                                      const SmallVectorImpl<unsigned> &Ops) {
+                                      const SmallVectorImpl<unsigned> &Ops,
+                                      MachineInstr *LoadMI) {
   // TargetInstrInfo::foldMemoryOperand only expects explicit, non-tied
   // operands.
   SmallVector<unsigned, 8> FoldOps;
@@ -262,11 +275,14 @@
       FoldOps.push_back(Idx);
   }
 
-  MachineInstr *FoldMI = tii_.foldMemoryOperand(MI, FoldOps, stackSlot_);
+  MachineInstr *FoldMI =
+                LoadMI ? tii_.foldMemoryOperand(MI, FoldOps, LoadMI)
+                       : tii_.foldMemoryOperand(MI, FoldOps, stackSlot_);
   if (!FoldMI)
     return false;
   lis_.ReplaceMachineInstrInMaps(MI, FoldMI);
-  vrm_.addSpillSlotUse(stackSlot_, FoldMI);
+  if (!LoadMI)
+    vrm_.addSpillSlotUse(stackSlot_, FoldMI);
   MI->eraseFromParent();
   DEBUG(dbgs() << "\tfolded: " << *FoldMI);
   return true;

Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.h?rev=122133&r1=122132&r2=122133&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.h (original)
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.h Fri Dec 17 21:04:14 2010
@@ -117,6 +117,12 @@
                             const TargetInstrInfo&,
                             const TargetRegisterInfo&);
 
+  /// markRematerialized - explicitly mark a value as rematerialized after doing
+  /// it manually.
+  void markRematerialized(VNInfo *ParentVNI) {
+    rematted_.insert(ParentVNI);
+  }
+
   /// didRematerialize - Return true if ParentVNI was rematerialized anywhere.
   bool didRematerialize(VNInfo *ParentVNI) const {
     return rematted_.count(ParentVNI);