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Rather than using a loop to calculate the interrupt vector, use the ctlz instruction.

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This commit is contained in:
Ali Saidi 2004-06-06 19:33:50 -04:00
parent 120825c1e2
commit ea03f8e35d
1 changed files with 7 additions and 24 deletions
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31
system/alpha/palcode/platform_m5.s
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@ -839,39 +839,22 @@ sys_int_21:
bis r8,r9,r8 bis r8,r9,r8
ldqp r9,0x0020(r8) // read PIC1 ISR for interrupting dev ldqp r9,0x0020(r8) // read PIC1 ISR for interrupting dev
#if 0 // we have a 21164 so this won't work because of the ctlz, if we ever change that...
normal_int: normal_int:
ctlz r9,r10 // count the number of leading zeros //ctlz r9,r10 // count the number of leading zeros
// EV5 doesn't have ctlz, but we do, so lets use it
.byte 0x4a
.byte 0x06
.byte 0xe9
.byte 0x73
lda r11,63(r31) lda r11,63(r31)
subq r11,r10,r17 // subtract from subq r11,r10,r17 // subtract from
lda r9,0x10(r31) lda r9,0x10(r31)
mulq r17,r9,r17 // compute 0x900 + (0x10 * Highest DIRn-bit) mulq r17,r9,r17 // compute 0x900 + (0x10 * Highest DIRn-bit)
lda r9,0x900(r31)
addq r17,r9,r17
br r31, pal_post_interrupt
#endif
normal_int:
or r31,63,r17 // load 63 into the counter
or r31,1,r11
sll r11,63,r11 // load a 1 into the msb
find_msb:
and r9,r11,r10
bne r10, found_msb
srl r11,1,r11
subl r17,1,r17
br r31, find_msb
found_msb:
lda r9,0x10(r31)
mulq r17,r9,r17 // compute offset + (0x10 * Highest DIRn-bit)
addq r17,r13,r17 addq r17,r13,r17
br r31, pal_post_interrupt br r31, pal_post_interrupt
ALIGN_BRANCH ALIGN_BRANCH
pal_post_dev_interrupt: pal_post_dev_interrupt:
or r13, r31, r17 // move vector to a1 or r13, r31, r17 // move vector to a1