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Fix sign extension as suggested by @foogod

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Also removes a branch from l8ui path, saves some cycles
This commit is contained in:
Angus Gratton 2015-09-14 18:30:11 +10:00
parent 44f2ba66e5
commit 390e007c75
1 changed files with 7 additions and 10 deletions
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17
core/exception_vectors.S
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@ -301,11 +301,7 @@ InnerLoadStoreExceptionHandler:
srl a3, a3 /* shift right correct distance */ srl a3, a3 /* shift right correct distance */
and a4, a3, a5 /* mask off bits we need for an l8/l16 */ and a4, a3, a5 /* mask off bits we need for an l8/l16 */
bbci a5, 14, .Lafter_extend_sign /* 8-bit, no sign extension */ bbsi a5, 14, .Lmaybe_extend_sign
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: .Lafter_extend_sign:
/* a2 holds instruction, 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 */ extui a2, a2, 4, 4 /* a2 now destination register 0-15 */
@ -347,11 +343,12 @@ InnerLoadStoreExceptionHandler:
rsr.excsave2 a0 // restore a0 saved in exception vector rsr.excsave2 a0 // restore a0 saved in exception vector
j .Lafter_increment_PC j .Lafter_increment_PC
.Lextend_sign: /* apply 16-bit sign extension if necessary .Lmaybe_extend_sign: /* apply 16-bit sign extension if necessary
a3 holds raw value, a4 holds masked */ a3 holds raw value, a4 holds masked */
bbci a3, 15, .Lafter_extend_sign /* sign bit not set, do nothing */ bbsi a5, 15, .Lafter_extend_sign /* 16-bit unsigned, no sign extension */
movi a3, (1<<31) bbci a3, 15, .Lafter_extend_sign /* sign bit not set, no sign extension */
or a4, a3, a4 /* set sign bit */ movi a3, 0xFFFF0000
or a4, a3, a4 /* set 32-bit sign bits */
j .Lafter_extend_sign j .Lafter_extend_sign
.Lwrite_value_direct_reg: .Lwrite_value_direct_reg: