Add coalescing to register allocator. A hint is added to each interval

which denotes the register we would like to be assigned to (virtual or
physical). In register allocation, if this hint exists and we can map
it to a physical register (it is either a physical register or it is a
virtual register that already got assigned to a physical one) we use
that register if it is available instead of a random one in the free
pool.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10634 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index cecfbbadbdfb98c832757f565df632cbcedf31e1..8f5fd3a648d94f56ebcc5a5609b678cd9cccb818 100644 (file)
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -38,6 +38,7 @@ namespace llvm {
             typedef std::pair<unsigned, unsigned> Range;
             typedef std::vector<Range> Ranges;
             unsigned reg;   // the register of this interval
+            unsigned hint;
             float weight;   // weight of this interval (number of uses
                             // * 10^loopDepth)
             Ranges ranges;  // the ranges this register is valid

diff --git a/include/llvm/CodeGen/LiveIntervals.h b/include/llvm/CodeGen/LiveIntervals.h
index cecfbbadbdfb98c832757f565df632cbcedf31e1..8f5fd3a648d94f56ebcc5a5609b678cd9cccb818 100644 (file)
--- a/include/llvm/CodeGen/LiveIntervals.h
+++ b/include/llvm/CodeGen/LiveIntervals.h
@@ -38,6 +38,7 @@ namespace llvm {
             typedef std::pair<unsigned, unsigned> Range;
             typedef std::vector<Range> Ranges;
             unsigned reg;   // the register of this interval
+            unsigned hint;
             float weight;   // weight of this interval (number of uses
                             // * 10^loopDepth)
             Ranges ranges;  // the ranges this register is valid

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index b34a65bc6443577dbd6b3b614ae86e52de804cde..4d0916046a0f4d45989d2913e19f8bd2856601b7 100644 (file)
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -108,6 +108,7 @@ bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
 
     // compute spill weights
     const LoopInfo& loopInfo = getAnalysis<LoopInfo>();
+    const TargetInstrInfo& tii = tm_->getInstrInfo();
 
     for (MbbIndex2MbbMap::iterator
              it = mbbi2mbbMap_.begin(), itEnd = mbbi2mbbMap_.end();
@@ -130,6 +131,21 @@ bool LiveIntervals::runOnMachineFunction(MachineFunction &fn) {
                 assert(r2iit != r2iMap_.end());
                 intervals_[r2iit->second].weight += pow(10.0F, loopDepth);
             }
+
+            // add hints for coalescing
+            unsigned src, dst;
+            if (tii.isMoveInstr(*instr, src, dst)) {
+                if (src >= MRegisterInfo::FirstVirtualRegister) {
+                    Reg2IntervalMap::iterator r2iit = r2iMap_.find(src);
+                    assert(r2iit != r2iMap_.end());
+                    intervals_[r2iit->second].hint = dst;
+                }
+                if (dst >= MRegisterInfo::FirstVirtualRegister) {
+                    Reg2IntervalMap::iterator r2iit = r2iMap_.find(dst);
+                    assert(r2iit != r2iMap_.end());
+                    intervals_[r2iit->second].hint = src;
+                }
+            }
         }
     }
 
@@ -329,7 +345,7 @@ void LiveIntervals::computeIntervals()
 }
 
 LiveIntervals::Interval::Interval(unsigned r)
-    : reg(r),
+    : reg(r), hint(0),
       weight((r < MRegisterInfo::FirstVirtualRegister ?
               std::numeric_limits<float>::max() : 0.0F))
 {

diff --git a/lib/CodeGen/LiveIntervalAnalysis.h b/lib/CodeGen/LiveIntervalAnalysis.h
index cecfbbadbdfb98c832757f565df632cbcedf31e1..8f5fd3a648d94f56ebcc5a5609b678cd9cccb818 100644 (file)
--- a/lib/CodeGen/LiveIntervalAnalysis.h
+++ b/lib/CodeGen/LiveIntervalAnalysis.h
@@ -38,6 +38,7 @@ namespace llvm {
             typedef std::pair<unsigned, unsigned> Range;
             typedef std::vector<Range> Ranges;
             unsigned reg;   // the register of this interval
+            unsigned hint;
             float weight;   // weight of this interval (number of uses
                             // * 10^loopDepth)
             Ranges ranges;  // the ranges this register is valid

diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index a804e1aa8697b96967885922f952c1daa1611d15..e2c1a18b4403969eb342ca321a24360026132775 100644 (file)
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -615,8 +615,19 @@ bool RA::physRegAvailable(unsigned physReg)
 unsigned RA::getFreePhysReg(Intervals::const_iterator cur)
 {
     DEBUG(std::cerr << "\t\tgetting free physical register: ");
-
     const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
+
+    if (unsigned reg = cur->hint) {
+        if (reg >= MRegisterInfo::FirstVirtualRegister &&
+            v2pMap_.find(reg) != v2pMap_.end())
+            reg = v2pMap_[reg];
+        if (reg && reg < MRegisterInfo::FirstVirtualRegister &&
+            mri_->getRegClass(reg) == rc && !regUse_[reg]) {
+            DEBUG(std::cerr << mri_->getName(reg) << '\n');
+            return reg;
+        }
+    }
+            
     for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_);
          i != rc->allocation_order_end(*mf_); ++i) {
         unsigned reg = *i;