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#-------------------------------------------------------------
# Context Stack Frame - 140 bytes / 35 words
#-------------------------------------------------------------       
#   0: R0
#   4: R1 (SP)
#   8: R2
#  12: R3 (ARG0)
#  16: R4
#  20: R5
#  24: R6
#  28: R7
#  32: R8
#  36: R9 (LR)
#  40: R10
#  44: R11
#  48: R12
#  52: R13
#  56: R14
#  60: R15
#  64: R16
#  68: R17
#  72: R18
#  76: R19
#  80: R20
#  84: R21
#  88: R22
#  92: R23
#  96: R24
# 100: R25
# 104: R26
# 108: R27
# 112: R28
# 116: R29
# 120: R30
# 124: R31
# 128: X
# 132: EPC
# 136: ESR  
#-------------------------------------------------------------    

#-------------------------------------------------------------
# asm_save_context:
#-------------------------------------------------------------    
.macro asm_save_context
   
    l.nop
    l.nop
    
    # Adjust SP (frame size is 140 + allow for 128 uncommitted in-use stack)
    l.addi  r1, r1, -268
    
    # Save register file to stack 
    l.sw 124(r1), r31
    l.sw 120(r1), r30
    l.sw 116(r1), r29
    l.sw 112(r1), r28
    l.sw 108(r1), r27
    l.sw 104(r1), r26
    l.sw 100(r1), r25
    l.sw 96(r1),  r24
    l.sw 92(r1),  r23
    l.sw 88(r1),  r22
    l.sw 84(r1),  r21
    l.sw 80(r1),  r20
    l.sw 76(r1),  r19
    l.sw 72(r1),  r18
    l.sw 68(r1),  r17
    l.sw 64(r1),  r16
    l.sw 60(r1),  r15
    l.sw 56(r1),  r14
    l.sw 52(r1),  r13
    l.sw 48(r1),  r12
    l.sw 44(r1),  r11
    l.sw 40(r1),  r10
    l.sw 36(r1),  r9
    l.sw 32(r1),  r8
    l.sw 28(r1),  r7
    l.sw 24(r1),  r6
    l.sw 20(r1),  r5
    l.sw 16(r1),  r4
    l.sw 12(r1),  r3
    l.sw 8(r1),   r2    
    l.sw 0(r1),   r0

    # R10 = EPC
    l.mfspr r10, r0, 32
    l.sw 132(r1),  r10

    # R10 = ESR
    l.mfspr r10, r0, 64
    l.sw 136(r1),  r10

    # Stack pointer (R1)
    l.or   r10, r0,  r1
    l.addi r10, r10, +268
    l.sw 4(r1), r10

.endm

#-------------------------------------------------------------
# asm_load_context:
#-------------------------------------------------------------        
.macro asm_load_context

    # Restore EPC (PC of non-exception code)
    l.lwz r10, 132(r1)
    
    # EPC = R10
    l.mtspr r0,r10,32
    
    # Restore ESR (SR of non-exception code)
    l.lwz r10, 136(r1)
    
    # ESR = R10
    l.mtspr r0,r10,64
    
    # Restore register set
    # r1/r1 already set
    l.lwz r2,   8(r1)
    l.lwz r3,  12(r1)
    l.lwz r4,  16(r1)
    l.lwz r5,  20(r1)
    l.lwz r6,  24(r1)
    l.lwz r7,  28(r1)
    l.lwz r8,  32(r1)
    l.lwz r9,  36(r1)
    l.lwz r10, 40(r1)
    l.lwz r11, 44(r1)
    l.lwz r12, 48(r1)
    l.lwz r13, 52(r1)
    l.lwz r14, 56(r1)
    l.lwz r15, 60(r1)
    l.lwz r16, 64(r1)
    l.lwz r17, 68(r1)
    l.lwz r18, 72(r1)
    l.lwz r19, 76(r1)
    l.lwz r20, 80(r1)
    l.lwz r21, 84(r1)
    l.lwz r22, 88(r1)
    l.lwz r23, 92(r1)
    l.lwz r24, 96(r1)
    l.lwz r25,100(r1)
    l.lwz r26,104(r1)
    l.lwz r27,108(r1)
    l.lwz r28,112(r1)
    l.lwz r29,116(r1)
    l.lwz r30,120(r1)
    l.lwz r31,124(r1)
    
    # Adjust SP past register set
    l.addi  r1, r1, +268
    
    # Return from interrupt (to restore PC & SR)
    l.rfe
    l.nop

.endm