Extend live debug values down the dominator tree by following copies.

The llvm.dbg.value intrinsic refers to SSA values, not virtual registers, so we
should be able to extend the range of a value by

Extend live debug values down the dominator tree by following copies.

The llvm.dbg.value intrinsic refers to SSA values, not virtual registers, so we
should be able to extend the range of a value by tracking that value through
register copies. This greatly improves the debug value tracking for function
arguments that for some reason are copied to a second virtual register at the
end of the entry block.

We only extend the debug value range where its register is killed. All original
llvm.dbg.value locations are still respected.

Copies from physical registers are ignored. That should not be a problem since
the entry block already adds DBG_VALUE instructions for the virtual registers
holding the function arguments.

llvm-svn: 127912

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DebugLoc associated with a machine instruction is used to emit location entries. DebugLoc associated with a DBG_VALUE is used to identify lexical scope of the variable. After register allocation, whi

DebugLoc associated with a machine instruction is used to emit location entries. DebugLoc associated with a DBG_VALUE is used to identify lexical scope of the variable. After register allocation, while inserting DBG_VALUE remember original debug location for the first instruction and reuse it, otherwise dwarf writer may be mislead in identifying the variable's scope.

llvm-svn: 124845

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Better terminator avoidance.

This approach also works when the terminator doesn't have a slot index. (Which
can happen??)

llvm-svn: 123413

Temporary workaround for an i386 crash in LiveDebugVariables.

llvm-svn: 123400

Try again enabling LiveDebugVariables.

llvm-svn: 123342

Don't emit a DBG_VALUE for a spill slot that the rewriter decided not to use after all.

llvm-svn: 123339

Fix braino in dominator tree walk.

llvm-svn: 123338

Sometimes, old virtual registers can linger on DBG_VALUE instructions.

Make sure we don't crash in that case, but simply turn them into %noreg instead.

llvm-svn: 123335

The world is not ready for LiveDebugVariables yet.

llvm-svn: 123290

Enable LiveDebugVariables by default.

llvm-svn: 123282

Don't insert DBG_VALUE instructions after the first terminator.

For one, MachineBasicBlock::getFirstTerminator() doesn't understand what is
happening, and it also makes sense to have all control flo

Don't insert DBG_VALUE instructions after the first terminator.

For one, MachineBasicBlock::getFirstTerminator() doesn't understand what is
happening, and it also makes sense to have all control flow run through the
DBG_VALUE.

llvm-svn: 123277

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Simplify a bunch of isVirtualRegister() and isPhysicalRegister() logic.

These functions not longer assert when passed 0, but simply return false instead.

No functional change intended.

llvm-svn: 1

Simplify a bunch of isVirtualRegister() and isPhysicalRegister() logic.

These functions not longer assert when passed 0, but simply return false instead.

No functional change intended.

llvm-svn: 123155

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Simplify LiveDebugVariables by storing MachineOperand copies locations instead
of using a Location class with the same information.

When making a copy of a MachineOperand that was already stored in

Simplify LiveDebugVariables by storing MachineOperand copies locations instead
of using a Location class with the same information.

When making a copy of a MachineOperand that was already stored in a
MachineInstr, it is necessary to clear the parent pointer on the copy. Otherwise
the register use-def lists become inconsistent.

Add MachineOperand::clearParent() to do that. An alternative would be a custom
MachineOperand copy constructor that cleared ParentMI. I didn't want to do that
because of the performance impact.

llvm-svn: 123109

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Replace TargetRegisterInfo::printReg with a PrintReg class that also works without a TRI instance.

Print virtual registers numbered from 0 instead of the arbitrary
FirstVirtualRegister. The first vi

Replace TargetRegisterInfo::printReg with a PrintReg class that also works without a TRI instance.

Print virtual registers numbered from 0 instead of the arbitrary
FirstVirtualRegister. The first virtual register is printed as %vreg0.
TRI::NoRegister is printed as %noreg.

llvm-svn: 123107

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Speculatively revert r123032.

llvm-svn: 123039

Appropriately truncate debug info range in dwarf output.
Enable live debug variables pass.

llvm-svn: 123032

Rename virtRegMap to avoid confusion with the VirtRegMap that it isn't.

llvm-svn: 120846

Coalesce debug locations when possible, causing less DBG_VALUE instructions to
be emitted.

llvm-svn: 120845

Emit DBG_VALUE instructions from LiveDebugVariables.

llvm-svn: 120842

Also update virtRegMap when renaming virtual registers.

llvm-svn: 120841

Update LiveDebugVariables during coalescing.

llvm-svn: 120720

Implement the first half of LiveDebugVariables.

Scan the MachineFunction for DBG_VALUE instructions, and replace them with a
data structure similar to LiveIntervals. The live range of a DBG_VALUE is

Implement the first half of LiveDebugVariables.

Scan the MachineFunction for DBG_VALUE instructions, and replace them with a
data structure similar to LiveIntervals. The live range of a DBG_VALUE is
determined by propagating it down the dominator tree until a new DBG_VALUE is
found. When a DBG_VALUE lives in a register, its live range is confined to the
live range of the register's value.

LiveDebugVariables runs before coalescing, so DBG_VALUEs are not artificially
extended when registers are joined.

The missing half will recreate DBG_VALUE instructions from the intervals when
register allocation is complete.

The pass is disabled by default. It can be enabled with the temporary command
line option -live-debug-variables.

llvm-svn: 120636

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Stub out a new LiveDebugVariables pass.

This analysis is going to run immediately after LiveIntervals. It will stay
alive during register allocation and keep track of user variables mentioned in
DBG

Stub out a new LiveDebugVariables pass.

This analysis is going to run immediately after LiveIntervals. It will stay
alive during register allocation and keep track of user variables mentioned in
DBG_VALUE instructions.

When the register allocator is moving values between registers and the stack, it
is very hard to keep track of DBG_VALUE instructions. We usually get it wrong.
This analysis maintains a data structure that makes it easy to update DBG_VALUE
instructions.

llvm-svn: 120385

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