rtm

Documentation

Overview

THESE PACKAGES ARE FOR DEMONSTRATION PURPOSES ONLY!

THEY DO NOT NOT CONTAIN WORKING INTRINSICS!

See https://github.com/klauspost/intrinsics

Index

• func Xabort(imm8 byte)
• func Xbegin() uint32
• func Xend()
• func Xtest() uint8

Functions

func Xabort

func Xabort(imm8 byte)

Xabort: Force an RTM abort. The EAX register is updated to reflect an XABORT instruction caused the abort, and the 'imm8' parameter will be provided in bits [31:24] of EAX.

Following an RTM abort, the logical processor resumes execution at the

fallback address computed through the outermost XBEGIN instruction.

IF RTM_ACTIVE = 0
	// nop
ELSE
	// restore architectural register state
	// discard memory updates performed in transaction
	// update EAX with status and imm8 value
	RTM_NEST_COUNT := 0
	RTM_ACTIVE := 0
	IF 64-bit Mode
		RIP := fallbackRIP
	ELSE
		EIP := fallbackEIP
	FI
FI

Instruction: 'XABORT'. Intrinsic: '_xabort'. Requires RTM.

FIXME: Requires compiler support (has immediate)

func Xbegin

func Xbegin() uint32

Xbegin: Specify the start of an RTM code region.

If the logical processor was not already in transactional execution, then

this call causes the logical processor to transition into transactional execution.

On an RTM abort, the logical processor discards all architectural register

and memory updates performed during the RTM execution, restores architectural state, and starts execution beginning at the fallback address computed from the outermost XBEGIN instruction.

IF RTM_NEST_COUNT < MAX_RTM_NEST_COUNT
	RTM_NEST_COUNT := RTM_NEST_COUNT + 1
	IF RTM_NEST_COUNT = 1
		IF 64-bit Mode
			fallbackRIP := RIP + SignExtend(IMM)
		ELSE IF 32-bit Mode
			fallbackEIP := EIP + SignExtend(IMM)
		ELSE // 16-bit Mode
			fallbackEIP := (EIP + SignExtend(IMM)) AND 0x0000FFFF
		FI

		RTM_ACTIVE := 1
		// enter RTM execution, record register state, start tracking memory state
	FI
ELSE
	// RTM abort (see _xabort)
FI

Instruction: 'XBEGIN'. Intrinsic: '_xbegin'. Requires RTM.

func Xend

func Xend()

Xend: Specify the end of an RTM code region.

If this corresponds to the outermost scope, the logical processor will

attempt to commit the logical processor state atomically.

If the commit fails, the logical processor will perform an RTM abort.

	IF RTM_ACTIVE = 1
		RTM_NEST_COUNT := RTM_NEST_COUNT - 1
		IF RTM_NEST_COUNT = 0
			// try to commit transaction
			IF fail to commit transaction
				// RTM abort (see _xabort)
			ELSE
				RTM_ACTIVE = 0
			FI
		FI
	FI

Instruction: 'XEND'. Intrinsic: '_xend'. Requires RTM.

func Xtest

func Xtest() uint8

Xtest: Query the transactional execution status, return 0 if inside a transactionally executing RTM or HLE region, and return 1 otherwise.

IF (RTM_ACTIVE = 1 OR HLE_ACTIVE = 1)
	dst := 0
ELSE
	dst := 1
FI

Instruction: 'XTEST'. Intrinsic: '_xtest'. Requires RTM.