In some cases, expand_expr_real_2 prefers to use the mode of the
caller-suggested target instead of the mode of the expression when
passing values to reduce_to_bit_field_precision. E.g.:
else if (target == 0)
op0 = convert_to_mode (mode, op0,
TYPE_UNSIGNED (TREE_TYPE
(treeop0)));
else
{
convert_move (target, op0,
TYPE_UNSIGNED (TREE_TYPE (treeop0)));
op0 = target;
}
where “op0” might not have “mode” for the “else” branch,
but does for all the others.
reduce_to_bit_field_precision discards the suggested target if it
has the wrong mode. This patch moves that to expand_expr_real_2
instead (conditional on reduce_bit_field).
Sorry for the breakage. This is what I'd done in the original
version of the patch, after checking all uses of REDUCE_BIT_FIELD.
I then forgot why it was necessary and tried to “simplify” the
patch for backports.
Tested on arm-linux-gnueabihf, where it restores bootstrap.
Other tests still ongoing. OK to install if it passes?
Richard
gcc/
PR middle-end/96151
* expr.c (expand_expr_real_2): When reducing bit fields,
clear the target if it has a different mode from the expression.
(reduce_to_bit_field_precision): Don't do that here. Instead
assert that the target already has the correct mode.
---
gcc/expr.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/gcc/expr.c b/gcc/expr.c
index 715edae819a..c7c3e9fd655 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -8664,7 +8664,9 @@ expand_expr_real_2 (sepops ops, rtx target, machine_mode
tmode,
reduce_bit_field = (INTEGRAL_TYPE_P (type)
&& !type_has_mode_precision_p (type));
- if (reduce_bit_field && modifier == EXPAND_STACK_PARM)
+ if (reduce_bit_field
+ && (modifier == EXPAND_STACK_PARM
+ || (target && GET_MODE (target) != mode)))
target = 0;
/* Use subtarget as the target for operand 0 of a binary operation. */
@@ -11527,9 +11529,8 @@ reduce_to_bit_field_precision (rtx exp, rtx target,
tree type)
{
scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
HOST_WIDE_INT prec = TYPE_PRECISION (type);
- gcc_assert (GET_MODE (exp) == VOIDmode || GET_MODE (exp) == mode);
- if (target && GET_MODE (target) != mode)
- target = 0;
+ gcc_assert ((GET_MODE (exp) == VOIDmode || GET_MODE (exp) == mode)
+ && (!target || GET_MODE (target) == mode));
/* For constant values, reduce using wide_int_to_tree. */
if (poly_int_rtx_p (exp))
