On 11/09/2016 09:22 PM, Laurent Vivier wrote:
Le 09/11/2016 à 20:39, Richard Henderson a écrit :
On 11/09/2016 07:47 PM, Richard Henderson wrote:
On 11/09/2016 06:30 PM, Laurent Vivier wrote:
+ /* create [src:X:..] */
+
+ tcg_gen_deposit_i32(t0, QREG_CC_X, src, 1, size);
+ tcg_gen_shli_i32(t0, t0, 31 - size);
+
+ /* rotate */
+
+ tcg_gen_rotl_i32(t0, t0, shift);
+
+ /* result is [src:..:src:X] */
+
+ tcg_gen_andi_i32(X, t0, 1);
+ tcg_gen_shri_i32(t0, t0, 1);
I don't see how this is supposed to work. If you form [src:x:...],
and rotate
by 0, then X gets garbage. Of course, you're actually forming
The result is ignored in the case of a rotate by 0 (see movcond in
rotate_reg()).
[0:src:x]. But
for a rol of 2, the lsb of src gets 0's instead of the msb of src.
for a rol of 2 on an 8bit value [12345678]:
tcg_gen_deposit_i32(t0, QREG_CC_X, src, 1, size);
tcg_gen_shli_i32(t0, t0, 31 - size);
t0 = [12345678x00000000000000000000000]
tcg_gen_rotl_i32(t0, t0, shift);
t0 = [345678x0000000000000000000000012]
tcg_gen_andi_i32(X, t0, 1);
X = 2
tcg_gen_shri_i32(t0, t0, 1);
t0 = [0345678x000000000000000000000001]
tcg_gen_shri_i32(t1, t0, 31 - size);
t1 = [000000000000000000000000345678x0]
tcg_gen_or_i32(dest, t0, t1);
dest = [0345678x0000000000000000345678x1]
-> we keep only 8 bits: [345678x1]
Where am I wrong?
You aren't. I simply misread this. But still we must only perform this rotate
modulo size+1.
r~
