llvm::RegPressureTracker

Synopsis

Declared in <llvm/CodeGen/RegisterPressure.h>

class RegPressureTracker;

Description

Remembers the high water mark within the region traversed. This does not automatically consider live-through ranges. The client may independently adjust for global liveness.

Each RegPressureTracker only works within a MachineBasicBlock. Pressure can be tracked across a larger region by storing a RegisterPressure result at each block boundary and explicitly adjusting pressure to account for block live-in and live-out register sets.

RegPressureTracker holds a reference to a RegisterPressure result that it computes incrementally. During downward tracking, P.BottomIdx or P.BottomPos is invalid until it reaches the end of the block or closeRegion() is explicitly called. Similarly, P.TopIdx is invalid during upward tracking. Changing direction has the side effect of closing region, and traversing past TopIdx or BottomIdx reopens it.

Member Functions

Name	Description
`RegPressureTracker` [constructor]	Constructors
`addLiveRegs`	Force the given registers to be live at the current position.
`advance`	`advance` overloads
`closeBottom`	Set the bottom boundary of the region and record live-out registers.
`closeRegion`	Finalize the region boundaries and recored live ins and live outs.
`closeTop`	Set the top boundary of the region and record live-in registers.
`decreaseRegPressure`	Decrease current pressure when lanes of `VRegOrUnit` become dead.
`dump`	Dump current and max register pressure to the debug stream.
`getDownwardPressure`	Get the pressure of each PSet after traversing this instruction top-down.
`getLiveThru`	Return the live-through pressure set values.
`getMaxDownwardPressureDelta`	Compute the max downward pressure delta for `MI.`
`getMaxPressureDelta`	Compute the max pressure delta for `MI` in the open tracking direction.
`getMaxUpwardPressureDelta`	Compute the max upward pressure delta for `MI.`
`getPos`	Get the MI position corresponding to this register pressure.
`getPressure`	`getPressure` overloads
`getPressureAfterInst`	Get the pressure of each PSet after traversing this instruction.
`getRegSetPressureAtPos`	Get the register set pressure at the current position, which may be less than the pressure across the traversed region.
`getUpwardPressure`	Get the pressure of each PSet after traversing this instruction bottom-up.
`getUpwardPressureDelta`	Compute the upward pressure delta for `MI` from a cached pressure diff.
`hasUntiedDef`	Return true if `VirtReg` has an untied definition in the tracked region.
`increaseRegPressure`	Increase current and max pressure when `VRegOrUnit` becomes live.
`init`	Initialize pressure tracking at `pos` in `mbb.`
`initLiveThru`	`initLiveThru` overloads
`isBottomClosed`	Return true if the bottom of the region has a valid position and live-outs.
`isTopClosed`	Return true if the top of the region has a valid position and live-ins.
`recede`	`recede` overloads
`recedeSkipDebugValues`	Recede until we find an instruction which is not a DebugValue.
`reset`	Reset the tracker so it can be initialized for another region.
`setPos`	Reset the MI position corresponding to the register pressure.

Protected Member Functions

Name	Description
`bumpDeadDefs`	Temporarily boost pressure for dead defs as a group, then drop it.
`bumpDownwardPressure`	Speculatively apply `MI's` downward pressure without discovering live-outs.
`bumpUpwardPressure`	Speculatively apply `MI's` upward pressure without discovering live-ins.
`discoverLiveIn`	Add Reg to the live in set and increase max pressure.
`discoverLiveInOrOut`	Add `Pair` to `LiveInOrOut` and increase max pressure for new lanes.
`discoverLiveOut`	Add Reg to the live out set and increase max pressure.
`getCurrSlot`	Get the SlotIndex for the first nondebug instruction including or after the current position.
`getLastUsedLanes`	Return lanes of `VRegOrUnit` last used at `Pos.`
`getLiveLanesAt`	Return lanes of `VRegOrUnit` that are live at `Pos.`
`getLiveThroughAt`	Return lanes of `VRegOrUnit` that live through the instruction at `Pos.`