RFWU — Return From Window Underflow

Instruction Word

Slot
Inst
6
3
6
2
6
1
6
0
5
9
5
8
5
7
5
6
5
5
5
4
5
3
5
2
5
1
5
0
4
9
4
8
4
7
4
6
4
5
4
4
4
3
4
2
4
1
4
0
3
9
3
8
3
7
3
6
3
5
3
4
3
3
3
2
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9876543210
Format x24 - 24 bit(s) 0
RFWU 000000000011010100000000

Assembler Syntax

RFWU

Description

(please consult the Xtensa ® Instruction Set Architecture Reference Manual for any cross references and additional information)

RFWU returns from an exception that went to one of the three window underflow vectors. It sets PS.EXCM back to 0, sets the WindowStart bit of the registers that were reloaded, restores WindowBase from PS.OWB, and then jumps to the address in EPC[1]. PS.UM is left unchanged.

RFWU is a privileged instruction.

Operation

if CRING != 0 then
	Exception (PrivilegedCause)
else
	PS.EXCM ← 0
	nextPC ← EPC[1]
	WindowStartWindowBase ← 1
	WindowBase ← PS.OWB
endif

Exceptions

EveryInst Group (see EveryInst Group:)GenExcep(PrivilegedCause) if Exception Option

Implementation Pipeline

In Out
EPC1 Estage, WindowBase Estage, WindowStart Estage, PSOWB Estage PSEXCM Estage, WindowBase Estage, WindowStart Estage