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[WebAssemby] Enforce FIFO ordering for instructions using stackified registers.

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llvm-svn: 253634
This commit is contained in:
Dan Gohman 2015-11-20 02:19:12 +00:00
parent e196b98966
commit 1b13c53f4b
2 changed files with 30 additions and 0 deletions
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26
lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
View File

@ -58,6 +58,18 @@ FunctionPass *llvm::createWebAssemblyRegStackify() {
return new WebAssemblyRegStackify();
}
// Decorate the given instruction with implicit operands that enforce the
// expression stack ordering constraints.
static void ImposeStackOrdering(MachineInstr *MI) {
// Read and write the opaque EXPR_STACK register.
MI->addOperand(MachineOperand::CreateReg(WebAssembly::EXPR_STACK,
/*isDef=*/true,
/*isImp=*/true));
MI->addOperand(MachineOperand::CreateReg(WebAssembly::EXPR_STACK,
/*isDef=*/false,
/*isImp=*/true));
}
bool WebAssemblyRegStackify::runOnMachineFunction(MachineFunction &MF) {
DEBUG(dbgs() << "********** Register Stackifying **********\n"
"********** Function: "
@ -80,6 +92,7 @@ bool WebAssemblyRegStackify::runOnMachineFunction(MachineFunction &MF) {
// Iterate through the inputs in reverse order, since we'll be pulling
// operands off the stack in FIFO order.
bool AnyStackified = false;
for (MachineOperand &Op : reverse(Insert->uses())) {
// We're only interested in explicit virtual register operands.
if (!Op.isReg() || Op.isImplicit())
@ -128,11 +141,13 @@ bool WebAssemblyRegStackify::runOnMachineFunction(MachineFunction &MF) {
continue;
Changed = true;
AnyStackified = true;
if (OneUse) {
// Move the def down and nest it in the current instruction.
MBB.insert(MachineBasicBlock::instr_iterator(Insert),
Def->removeFromParent());
MFI.stackifyVReg(Reg);
ImposeStackOrdering(Def);
Insert = Def;
} else {
// Clone the def down and nest it in the current instruction.
@ -145,11 +160,22 @@ bool WebAssemblyRegStackify::runOnMachineFunction(MachineFunction &MF) {
Clone->getOperand(0).setReg(NewReg);
MBB.insert(MachineBasicBlock::instr_iterator(Insert), Clone);
MFI.stackifyVReg(Reg);
ImposeStackOrdering(Clone);
Insert = Clone;
}
}
if (AnyStackified)
ImposeStackOrdering(&MI);
}
}
// If we used EXPR_STACK anywhere, add it to the live-in sets everywhere
// so that it never looks like a use-before-def.
if (Changed) {
MF.getRegInfo().addLiveIn(WebAssembly::EXPR_STACK);
for (MachineBasicBlock &MBB : MF)
MBB.addLiveIn(WebAssembly::EXPR_STACK);
}
return Changed;
}

4
lib/Target/WebAssembly/WebAssemblyRegisterInfo.td
View File

@ -39,6 +39,10 @@ def SP64 : WebAssemblyReg<"%SP64">;
def F32_0 : WebAssemblyReg<"%f32.0">;
def F64_0 : WebAssemblyReg<"%f64.0">;
// The expression stack "register". This is an opaque entity which serves to
// order uses and defs that must remain in FIFO order.
def EXPR_STACK : WebAssemblyReg<"STACK">;
//===----------------------------------------------------------------------===//
// Register classes
//===----------------------------------------------------------------------===//