From 8c47ad8c4708286bda9362f8089f84a3d7e41056 Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Sat, 21 Jan 2012 00:58:53 +0000
Subject: Handle register masks in LiveVariables.

A register mask operand kills any live physreg that isn't preserved.
Unlike an implicit-def operand, the clobbered physregs are never live
afterwards.

This means LiveVariables has to track a much smaller number of live
physregs, and it should spend much less time in addRegisterDead().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148609 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/LiveVariables.h |  3 +++
 lib/CodeGen/LiveVariables.cpp        | 30 ++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/include/llvm/CodeGen/LiveVariables.h b/include/llvm/CodeGen/LiveVariables.h
index 71062a2a51..d4bb409e06 100644
--- a/include/llvm/CodeGen/LiveVariables.h
+++ b/include/llvm/CodeGen/LiveVariables.h
@@ -160,6 +160,9 @@ private:   // Intermediate data structures
   /// the last use of the whole register.
   bool HandlePhysRegKill(unsigned Reg, MachineInstr *MI);
 
+  /// HandleRegMask - Call HandlePhysRegKill for all registers clobbered by Mask.
+  void HandleRegMask(const MachineOperand&);
+
   void HandlePhysRegUse(unsigned Reg, MachineInstr *MI);
   void HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
                         SmallVector<unsigned, 4> &Defs);
diff --git a/lib/CodeGen/LiveVariables.cpp b/lib/CodeGen/LiveVariables.cpp
index 77df27cc97..54b9cc18f8 100644
--- a/lib/CodeGen/LiveVariables.cpp
+++ b/lib/CodeGen/LiveVariables.cpp
@@ -417,6 +417,27 @@ bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
   return true;
 }
 
+void LiveVariables::HandleRegMask(const MachineOperand &MO) {
+  // Call HandlePhysRegKill() for all live registers clobbered by Mask.
+  // Clobbered registers are always dead, sp there is no need to use
+  // HandlePhysRegDef().
+  for (unsigned Reg = 1, NumRegs = TRI->getNumRegs(); Reg != NumRegs; ++Reg) {
+    // Skip dead regs.
+    if (!PhysRegDef[Reg] && !PhysRegUse[Reg])
+      continue;
+    // Skip mask-preserved regs.
+    if (!MO.clobbersPhysReg(Reg));
+      continue;
+    // Kill the largest clobbered super-register.
+    // This avoids needless implicit operands.
+    unsigned Super = Reg;
+    for (const unsigned *SR = TRI->getSuperRegisters(Reg); *SR; ++SR)
+      if ((PhysRegDef[*SR] || PhysRegUse[*SR]) && MO.clobbersPhysReg(*SR))
+        Super = *SR;
+    HandlePhysRegKill(Super, 0);
+  }
+}
+
 void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
                                      SmallVector<unsigned, 4> &Defs) {
   // What parts of the register are previously defined?
@@ -534,8 +555,13 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
       // Clear kill and dead markers. LV will recompute them.
       SmallVector<unsigned, 4> UseRegs;
       SmallVector<unsigned, 4> DefRegs;
+      SmallVector<unsigned, 1> RegMasks;
       for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
         MachineOperand &MO = MI->getOperand(i);
+        if (MO.isRegMask()) {
+          RegMasks.push_back(i);
+          continue;
+        }
         if (!MO.isReg() || MO.getReg() == 0)
           continue;
         unsigned MOReg = MO.getReg();
@@ -557,6 +583,10 @@ bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
           HandlePhysRegUse(MOReg, MI);
       }
 
+      // Process all masked registers. (Call clobbers).
+      for (unsigned i = 0, e = RegMasks.size(); i != e; ++i)
+        HandleRegMask(MI->getOperand(RegMasks[i]));
+
       // Process all defs.
       for (unsigned i = 0, e = DefRegs.size(); i != e; ++i) {
         unsigned MOReg = DefRegs[i];
-- 
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