https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78660
YunQiang Su <syq at debian dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |syq at debian dot org
--- Comment #6 from YunQiang Su <syq at debian dot org> ---
With revert some change, with patch:
Index: gcc-7-7-20161217/src/gcc/combine.c
===================================================================
--- gcc-7-7-20161217.orig/src/gcc/combine.c
+++ gcc-7-7-20161217/src/gcc/combine.c
@@ -9972,13 +9972,13 @@ reg_nonzero_bits_for_combine (const_rtx
(DF_LR_IN (ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb),
REGNO (x)))))
{
- /* Note that, even if the precision of last_set_mode is lower than that
- of mode, record_value_for_reg invoked nonzero_bits on the register
- with nonzero_bits_mode (because last_set_mode is necessarily integral
- and HWI_COMPUTABLE_MODE_P in this case) so bits in nonzero_bits_mode
- are all valid, hence in mode too since nonzero_bits_mode is defined
- to the largest HWI_COMPUTABLE_MODE_P mode. */
- *nonzero &= rsp->last_set_nonzero_bits;
+ unsigned HOST_WIDE_INT mask = rsp->last_set_nonzero_bits;
+
+ if (GET_MODE_PRECISION (rsp->last_set_mode) < GET_MODE_PRECISION (mode))
+ /* We don't know anything about the upper bits. */
+ mask |= GET_MODE_MASK (mode) ^ GET_MODE_MASK (rsp->last_set_mode);
+
+ *nonzero &= mask;
return NULL;
}
