Implement the local-dynamic TLS model for x86 (PR3985)
This implements codegen support for accesses to thread-local variables
using the local-dynamic model, and adds a clean-up pass so that the base
address for the TLS block can be re-used between local-dynamic access on
an execution path.
llvm-svn: 157818
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index ae0c921..ad7521c 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -21,6 +21,7 @@
#include "llvm/LLVMContext.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -3990,9 +3991,126 @@
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
+
+ private:
+ unsigned BaseReg;
};
}
char CGBR::ID = 0;
FunctionPass*
llvm::createGlobalBaseRegPass() { return new CGBR(); }
+
+namespace {
+ struct LDTLSCleanup : public MachineFunctionPass {
+ static char ID;
+ LDTLSCleanup() : MachineFunctionPass(ID) {}
+
+ virtual bool runOnMachineFunction(MachineFunction &MF) {
+ X86MachineFunctionInfo* MFI = MF.getInfo<X86MachineFunctionInfo>();
+ if (MFI->getNumLocalDynamicTLSAccesses() < 2) {
+ // No point folding accesses if there isn't at least two.
+ return false;
+ }
+
+ MachineDominatorTree *DT = &getAnalysis<MachineDominatorTree>();
+ return VisitNode(DT->getRootNode(), 0);
+ }
+
+ // Visit the dominator subtree rooted at Node in pre-order.
+ // If TLSBaseAddrReg is non-null, then use that to replace any
+ // TLS_base_addr instructions. Otherwise, create the register
+ // when the first such instruction is seen, and then use it
+ // as we encounter more instructions.
+ bool VisitNode(MachineDomTreeNode *Node, unsigned TLSBaseAddrReg) {
+ MachineBasicBlock *BB = Node->getBlock();
+ bool Changed = false;
+
+ // Traverse the current block.
+ for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end(); I != E;
+ ++I) {
+ switch (I->getOpcode()) {
+ case X86::TLS_base_addr32:
+ case X86::TLS_base_addr64:
+ if (TLSBaseAddrReg)
+ I = ReplaceTLSBaseAddrCall(I, TLSBaseAddrReg);
+ else
+ I = SetRegister(I, &TLSBaseAddrReg);
+ Changed = true;
+ break;
+ default:
+ break;
+ }
+ }
+
+ // Visit the children of this block in the dominator tree.
+ for (MachineDomTreeNode::iterator I = Node->begin(), E = Node->end();
+ I != E; ++I) {
+ Changed |= VisitNode(*I, TLSBaseAddrReg);
+ }
+
+ return Changed;
+ }
+
+ // Replace the TLS_base_addr instruction I with a copy from
+ // TLSBaseAddrReg, returning the new instruction.
+ MachineInstr *ReplaceTLSBaseAddrCall(MachineInstr *I,
+ unsigned TLSBaseAddrReg) {
+ MachineFunction *MF = I->getParent()->getParent();
+ const X86TargetMachine *TM =
+ static_cast<const X86TargetMachine *>(&MF->getTarget());
+ const bool is64Bit = TM->getSubtarget<X86Subtarget>().is64Bit();
+ const X86InstrInfo *TII = TM->getInstrInfo();
+
+ // Insert a Copy from TLSBaseAddrReg to RAX/EAX.
+ MachineInstr *Copy = BuildMI(*I->getParent(), I, I->getDebugLoc(),
+ TII->get(TargetOpcode::COPY),
+ is64Bit ? X86::RAX : X86::EAX)
+ .addReg(TLSBaseAddrReg);
+
+ // Erase the TLS_base_addr instruction.
+ I->eraseFromParent();
+
+ return Copy;
+ }
+
+ // Create a virtal register in *TLSBaseAddrReg, and populate it by
+ // inserting a copy instruction after I. Returns the new instruction.
+ MachineInstr *SetRegister(MachineInstr *I, unsigned *TLSBaseAddrReg) {
+ MachineFunction *MF = I->getParent()->getParent();
+ const X86TargetMachine *TM =
+ static_cast<const X86TargetMachine *>(&MF->getTarget());
+ const bool is64Bit = TM->getSubtarget<X86Subtarget>().is64Bit();
+ const X86InstrInfo *TII = TM->getInstrInfo();
+
+ // Create a virtual register for the TLS base address.
+ MachineRegisterInfo &RegInfo = MF->getRegInfo();
+ *TLSBaseAddrReg = RegInfo.createVirtualRegister(is64Bit
+ ? &X86::GR64RegClass
+ : &X86::GR32RegClass);
+
+ // Insert a copy from RAX/EAX to TLSBaseAddrReg.
+ MachineInstr *Next = I->getNextNode();
+ MachineInstr *Copy = BuildMI(*I->getParent(), Next, I->getDebugLoc(),
+ TII->get(TargetOpcode::COPY),
+ *TLSBaseAddrReg)
+ .addReg(is64Bit ? X86::RAX : X86::EAX);
+
+ return Copy;
+ }
+
+ virtual const char *getPassName() const {
+ return "Local Dynamic TLS Access Clean-up";
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ AU.addRequired<MachineDominatorTree>();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+ };
+}
+
+char LDTLSCleanup::ID = 0;
+FunctionPass*
+llvm::createCleanupLocalDynamicTLSPass() { return new LDTLSCleanup(); }