1 files changed, 15 insertions, 9 deletions
diff --git a/lib/CodeGen/CalcSpillWeights.cpp b/lib/CodeGen/CalcSpillWeights.cpp
index 4925c4db1e0a..bc033f96bcf2 100644
--- a/lib/CodeGen/CalcSpillWeights.cpp
+++ b/lib/CodeGen/CalcSpillWeights.cpp
@@ -7,8 +7,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#define DEBUG_TYPE "calcspillweights"
-
 #include "llvm/CodeGen/CalcSpillWeights.h"
 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
@@ -22,6 +20,8 @@
 #include "llvm/Target/TargetRegisterInfo.h"
 using namespace llvm;
 
+#define DEBUG_TYPE "calcspillweights"
+
 void llvm::calculateSpillWeightsAndHints(LiveIntervals &LIS,
                            MachineFunction &MF,
                            const MachineLoopInfo &MLI,
@@ -96,8 +96,8 @@ void
 VirtRegAuxInfo::calculateSpillWeightAndHint(LiveInterval &li) {
   MachineRegisterInfo &mri = MF.getRegInfo();
   const TargetRegisterInfo &tri = *MF.getTarget().getRegisterInfo();
-  MachineBasicBlock *mbb = 0;
-  MachineLoop *loop = 0;
+  MachineBasicBlock *mbb = nullptr;
+  MachineLoop *loop = nullptr;
   bool isExiting = false;
   float totalWeight = 0;
   SmallPtrSet<MachineInstr*, 8> visited;
@@ -112,8 +112,10 @@ VirtRegAuxInfo::calculateSpillWeightAndHint(LiveInterval &li) {
   // Don't recompute spill weight for an unspillable register.
   bool Spillable = li.isSpillable();
 
-  for (MachineRegisterInfo::reg_iterator I = mri.reg_begin(li.reg);
-       MachineInstr *mi = I.skipInstruction();) {
+  for (MachineRegisterInfo::reg_instr_iterator
+       I = mri.reg_instr_begin(li.reg), E = mri.reg_instr_end();
+       I != E; ) {
+    MachineInstr *mi = &*(I++);
     if (mi->isIdentityCopy() || mi->isImplicitDef() || mi->isDebugValue())
       continue;
     if (!visited.insert(mi))
@@ -130,9 +132,9 @@ VirtRegAuxInfo::calculateSpillWeightAndHint(LiveInterval &li) {
 
       // Calculate instr weight.
       bool reads, writes;
-      tie(reads, writes) = mi->readsWritesVirtualRegister(li.reg);
+      std::tie(reads, writes) = mi->readsWritesVirtualRegister(li.reg);
       weight = LiveIntervals::getSpillWeight(
-          writes, reads, MBFI.getBlockFreq(mi->getParent()));
+        writes, reads, &MBFI, mi);
 
       // Give extra weight to what looks like a loop induction variable update.
       if (writes && isExiting && LIS.isLiveOutOfMBB(li, mbb))
@@ -147,7 +149,11 @@ VirtRegAuxInfo::calculateSpillWeightAndHint(LiveInterval &li) {
     unsigned hint = copyHint(mi, li.reg, tri, mri);
     if (!hint)
       continue;
-    float hweight = Hint[hint] += weight;
+    // Force hweight onto the stack so that x86 doesn't add hidden precision,
+    // making the comparison incorrectly pass (i.e., 1 > 1 == true??).
+    //
+    // FIXME: we probably shouldn't use floats at all.
+    volatile float hweight = Hint[hint] += weight;
     if (TargetRegisterInfo::isPhysicalRegister(hint)) {
       if (hweight > bestPhys && mri.isAllocatable(hint))
         bestPhys = hweight, hintPhys = hint;