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Unaligned load: Shave a few more instructions off

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This commit is contained in:
Angus Gratton 2015-08-11 16:25:11 +10:00
parent 3b3f5ea771
commit e3b24df043
1 changed files with 11 additions and 13 deletions
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24
core/exception_vectors.S
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@ -268,7 +268,7 @@ PRINT_MULTI:
.global UserLoadStoreExceptionHandler
/* "Fix" LoadStoreException exceptions thatare l8/l16 from an Instruction region */
UserLoadStoreExceptionHandler:
addi sp, sp, -0x40
addi sp, sp, -0x18
s32i a2, sp, 0x08
s32i a3, sp, 0x0c
s32i a4, sp, 0x10
@ -284,7 +284,7 @@ UserLoadStoreExceptionHandler:
l32i a4, a2, 4
src a2, a4, a3 // a2 now instruction that failed
/* Check if a2 matches l8ui or l16ui */
/* Check if a2 matches l8ui, l16ui or l16si opcodes */
movi a3, 0x00F00F /* opcode mask */
and a3, a2, a3
beqi a3, 0x000002, .Lcan_fix_8bit /* l8ui opcode after masking */
@ -320,18 +320,17 @@ TODO: the exception dump will have some wrong values in it */
movi a4, ~3
and a3, a3, a4 /* a3 now word aligned read address */
/* Sanity check the top nibble of the faulting address is 4, otherwise
we can't help out here */
extui a4, a3, 28, 4
bnei a4, 0x4, .Lcant_fix
l32i a3, a3, 0 /* perform the actual read */
srl a3, a3 /* shift right correct distance */
and a4, a3, a5 /* mask off bits we need for an l8/l16 */
bbci a5, 15, .Lextend_sign
bbci a5, 14, .Lafter_extend_sign /* 8-bit, no sign extension */
bbsi a5, 15, .Lafter_extend_sign /* 16-bit unsigned, no sign extension */
bbci a3, 15, .Lafter_extend_sign /* sign bit not set, no sign extension */
movi a3, (1<<31)
or a4, a3, a4 /* set 32-bit sign bit */
.Lafter_extend_sign:
/* a4 holds the correctly read value */
/* a2 holds instruction, a4 holds the correctly read value */
extui a2, a2, 4, 4 /* a2 now destination register 0-15 */
/* test if a4 needs to be written directly to a register (ie not a working register) */
@ -339,9 +338,8 @@ TODO: the exception dump will have some wrong values in it */
/* test if a4 needs to be written to a0 */
beqz a2, .Lwrite_value_a0_reg
/* otherwise, a4 needs to be written to a saved working register 'slot' on the stack */
slli a2, a2, 2
add a5, sp, a2
/* otherwise, a4 can be written to a saved working register 'slot' on the stack */
addx4 a5, a2, sp
s32i a4, a5, 0
.Lafter_write_value:
@ -359,7 +357,7 @@ TODO: the exception dump will have some wrong values in it */
l32i a3, sp, 0x0c
l32i a4, sp, 0x10
l32i a5, sp, 0x14
addi sp, sp, 0x40
addi sp, sp, 0x18
rfe
.Lextend_sign: /* apply 16-bit sign extension if necessary