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tcg/optimize: fix known-zero bits for right shift ops 

32-bit versions of sar and shr ops should not propagate known-zero bits
from the unused 32 high bits. For sar it could even lead to wrong code
being generated.

Cc: qemu-stable@nongnu.org
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Aurelien Jarno 2013-09-03 08:27:38 +02:00 committed by Richard Henderson
parent 7a3a00979d
commit e46b225a31
1 changed files with 14 additions and 5 deletions
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19
tcg/optimize.c
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@ -726,16 +726,25 @@ static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
mask = temps[args[1]].mask & mask;
break;
CASE_OP_32_64(sar):
case INDEX_op_sar_i32:
if (temps[args[2]].state == TCG_TEMP_CONST) {
mask = ((tcg_target_long)temps[args[1]].mask
>> temps[args[2]].val);
mask = (int32_t)temps[args[1]].mask >> temps[args[2]].val;
}
break;
case INDEX_op_sar_i64:
if (temps[args[2]].state == TCG_TEMP_CONST) {
mask = (int64_t)temps[args[1]].mask >> temps[args[2]].val;
}
break;
CASE_OP_32_64(shr):
case INDEX_op_shr_i32:
if (temps[args[2]].state == TCG_TEMP_CONST) {
mask = temps[args[1]].mask >> temps[args[2]].val;
mask = (uint32_t)temps[args[1]].mask >> temps[args[2]].val;
}
break;
case INDEX_op_shr_i64:
if (temps[args[2]].state == TCG_TEMP_CONST) {
mask = (uint64_t)temps[args[1]].mask >> temps[args[2]].val;
}
break;