R600/SI: Special case v_mov_b32 as really rematerializable

[oota-llvm.git] / lib / Target / R600 / SIFixSGPRCopies.cpp

diff --git a/lib/Target/R600/SIFixSGPRCopies.cpp b/lib/Target/R600/SIFixSGPRCopies.cpp
index c108571fcfb7f9283c3c8bed91e3a80b70535c8f..cd1b3acc5c87a90e57f6d44588124eadb6694dab 100644 (file)
--- a/lib/Target/R600/SIFixSGPRCopies.cpp
+++ b/lib/Target/R600/SIFixSGPRCopies.cpp
@@ -136,12 +136,12 @@ const TargetRegisterClass *SIFixSGPRCopies::inferRegClassFromUses(
                                                  const MachineRegisterInfo &MRI,
                                                  unsigned Reg,
                                                  unsigned SubReg) const {
-  // The Reg parameter to the function must always be defined by either a PHI
-  // or a COPY, therefore it cannot be a physical register.
-  assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
-         "Reg cannot be a physical register");
 
-  const TargetRegisterClass *RC = MRI.getRegClass(Reg);
+  const TargetRegisterClass *RC
+    = TargetRegisterInfo::isVirtualRegister(Reg) ?
+    MRI.getRegClass(Reg) :
+    TRI->getRegClass(Reg);
+
   RC = TRI->getSubRegClass(RC, SubReg);
   for (MachineRegisterInfo::use_instr_iterator
        I = MRI.use_instr_begin(Reg), E = MRI.use_instr_end(); I != E; ++I) {
@@ -182,7 +182,12 @@ bool SIFixSGPRCopies::isVGPRToSGPRCopy(const MachineInstr &Copy,
   unsigned DstReg = Copy.getOperand(0).getReg();
   unsigned SrcReg = Copy.getOperand(1).getReg();
   unsigned SrcSubReg = Copy.getOperand(1).getSubReg();
-  const TargetRegisterClass *DstRC = MRI.getRegClass(DstReg);
+
+  const TargetRegisterClass *DstRC
+    = TargetRegisterInfo::isVirtualRegister(DstReg) ?
+    MRI.getRegClass(DstReg) :
+    TRI->getRegClass(DstReg);
+
   const TargetRegisterClass *SrcRC;
 
   if (!TargetRegisterInfo::isVirtualRegister(SrcReg) ||
@@ -217,20 +222,21 @@ bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
       switch (MI.getOpcode()) {
       default: continue;
       case AMDGPU::PHI: {
-        DEBUG(dbgs() << " Fixing PHI:\n");
-        DEBUG(MI.print(dbgs()));
+        DEBUG(dbgs() << "Fixing PHI: " << MI);
 
-        for (unsigned i = 1; i < MI.getNumOperands(); i+=2) {
-          unsigned Reg = MI.getOperand(i).getReg();
-          const TargetRegisterClass *RC = inferRegClassFromDef(TRI, MRI, Reg,
-                                                  MI.getOperand(0).getSubReg());
-          MRI.constrainRegClass(Reg, RC);
+        for (unsigned i = 1; i < MI.getNumOperands(); i += 2) {
+          const MachineOperand &Op = MI.getOperand(i);
+          unsigned Reg = Op.getReg();
+          const TargetRegisterClass *RC
+            = inferRegClassFromDef(TRI, MRI, Reg, Op.getSubReg());
+
+          MRI.constrainRegClass(Op.getReg(), RC);
         }
         unsigned Reg = MI.getOperand(0).getReg();
         const TargetRegisterClass *RC = inferRegClassFromUses(TRI, MRI, Reg,
                                                   MI.getOperand(0).getSubReg());
-        if (TRI->getCommonSubClass(RC, &AMDGPU::VReg_32RegClass)) {
-          MRI.constrainRegClass(Reg, &AMDGPU::VReg_32RegClass);
+        if (TRI->getCommonSubClass(RC, &AMDGPU::VGPR_32RegClass)) {
+          MRI.constrainRegClass(Reg, &AMDGPU::VGPR_32RegClass);
         }
 
         if (!TRI->isSGPRClass(MRI.getRegClass(Reg)))
@@ -238,14 +244,66 @@ bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
 
         // If a PHI node defines an SGPR and any of its operands are VGPRs,
         // then we need to move it to the VALU.
+        //
+        // Also, if a PHI node defines an SGPR and has all SGPR operands
+        // we must move it to the VALU, because the SGPR operands will
+        // all end up being assigned the same register, which means
+        // there is a potential for a conflict if different threads take
+        // different control flow paths.
+        //
+        // For Example:
+        //
+        // sgpr0 = def;
+        // ...
+        // sgpr1 = def;
+        // ...
+        // sgpr2 = PHI sgpr0, sgpr1
+        // use sgpr2;
+        //
+        // Will Become:
+        //
+        // sgpr2 = def;
+        // ...
+        // sgpr2 = def;
+        // ...
+        // use sgpr2
+        //
+        // FIXME: This is OK if the branching decision is made based on an
+        // SGPR value.
+        bool SGPRBranch = false;
+
+        // The one exception to this rule is when one of the operands
+        // is defined by a SI_BREAK, SI_IF_BREAK, or SI_ELSE_BREAK
+        // instruction.  In this case, there we know the program will
+        // never enter the second block (the loop) without entering
+        // the first block (where the condition is computed), so there
+        // is no chance for values to be over-written.
+
+        bool HasBreakDef = false;
         for (unsigned i = 1; i < MI.getNumOperands(); i+=2) {
           unsigned Reg = MI.getOperand(i).getReg();
           if (TRI->hasVGPRs(MRI.getRegClass(Reg))) {
             TII->moveToVALU(MI);
             break;
           }
+          MachineInstr *DefInstr = MRI.getUniqueVRegDef(Reg);
+          assert(DefInstr);
+          switch(DefInstr->getOpcode()) {
+
+          case AMDGPU::SI_BREAK:
+          case AMDGPU::SI_IF_BREAK:
+          case AMDGPU::SI_ELSE_BREAK:
+          // If we see a PHI instruction that defines an SGPR, then that PHI
+          // instruction has already been considered and should have
+          // a *_BREAK as an operand.
+          case AMDGPU::PHI:
+            HasBreakDef = true;
+            break;
+          }
         }
 
+        if (!SGPRBranch && !HasBreakDef)
+          TII->moveToVALU(MI);
         break;
       }
       case AMDGPU::REG_SEQUENCE: {
@@ -253,8 +311,7 @@ bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
             !hasVGPROperands(MI, TRI))
           continue;
 
-        DEBUG(dbgs() << "Fixing REG_SEQUENCE:\n");
-        DEBUG(MI.print(dbgs()));
+        DEBUG(dbgs() << "Fixing REG_SEQUENCE: " << MI);
 
         TII->moveToVALU(MI);
         break;
@@ -266,8 +323,7 @@ bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
         Src1RC = MRI.getRegClass(MI.getOperand(2).getReg());
         if (TRI->isSGPRClass(DstRC) &&
             (TRI->hasVGPRs(Src0RC) || TRI->hasVGPRs(Src1RC))) {
-          DEBUG(dbgs() << " Fixing INSERT_SUBREG:\n");
-          DEBUG(MI.print(dbgs()));
+          DEBUG(dbgs() << " Fixing INSERT_SUBREG: " << MI);
           TII->moveToVALU(MI);
         }
         break;
@@ -275,5 +331,6 @@ bool SIFixSGPRCopies::runOnMachineFunction(MachineFunction &MF) {
       }
     }
   }
-  return false;
+
+  return true;
 }