I have been adding rotate capability to AVR port and have come across what I
think is bug in
optabs.c: expand_binop()
This occurs during a rotate expansion. For example
target = op0 rotated by op1
In the particular situation (code extract below) it tries a reverse rotate
of (bits - op1). Where this expression is expanded as a simple integer,
a negation or subtraction depending on type of op1 and target.
The expansion of the subtraction is using the mode of the target - I believe
it should be using the mode of op1.
The mode of the rotation amount need not be the same as the target.
target:DI = Op0:DI rotate op1:HI
In my testcase it is not and I get asserts latter in simplfy_rtx.
The negation mode looks equally wrong.
Am I mistaken?
/* If we were trying to rotate, and that didn't work, try rotating
the other direction before falling back to shifts and bitwise-or. */
if (((binoptab == rotl_optab
&& optab_handler (rotr_optab, mode)->insn_code != CODE_FOR_nothing)
|| (binoptab == rotr_optab
&& optab_handler (rotl_optab, mode)->insn_code != CODE_FOR_nothing))
&& mclass == MODE_INT)
{
optab otheroptab = (binoptab == rotl_optab ? rotr_optab : rotl_optab);
rtx newop1;
unsigned int bits = GET_MODE_BITSIZE (mode);
if (CONST_INT_P (op1))
newop1 = GEN_INT (bits - INTVAL (op1));
else if (targetm.shift_truncation_mask (mode) == bits - 1)
newop1 = negate_rtx (mode, op1);
else
newop1 = expand_binop (mode, sub_optab,
GEN_INT (bits), op1,
NULL_RTX, unsignedp, OPTAB_DIRECT);