lower-bitint: Avoid sign-extending cast to unsigned types feeding div/mod/float [PR113614]

The following testcase is miscompiled, because some narrower value
is sign-extended to wider unsigned _BitInt used as division operand.
handle_operand_addr for that case returns the narrower value and
precision -prec_of_narrower_value.  That works fine for multiplication
(at least, normal multiplication, but we don't merge casts with
.MUL_OVERFLOW or the ubsan multiplication right now), because the
result is the same whether we treat the arguments as signed or unsigned.
But is completely wrong for division/modulo or conversions to
floating-point, if we pass negative prec for an input operand of a libgcc
handler, those treat it like a negative number, not an unsigned one
sign-extended from something smaller (and it doesn't know to what precision
it has been extended).

So, the following patch fixes it by making sure we don't merge such
sign-extensions to unsigned _BitInt type with division, modulo or
conversions to floating point.

2024-01-27  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113614
	* gimple-lower-bitint.cc (gimple_lower_bitint): Don't merge
	widening casts from signed to unsigned types with TRUNC_DIV_EXPR,
	TRUNC_MOD_EXPR or FLOAT_EXPR uses.

	* gcc.dg/torture/bitint-54.c: New test.

0 files changed, 0 insertions, 0 deletions