https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106746
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |richard.sandiford at arm dot
com,
| |roger at nextmovesoftware dot
com,
| |segher at kernel dot
crashing.org
--- Comment #6 from H.J. Lu <hjl.tools at gmail dot com> ---
Revert
diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index fa20665bb01..7d09bf7103d 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -1615,6 +1639,24 @@ simplify_context::simplify_unary_operation_1 (rtx_code
co
de, machine_mode mode,
}
}
+ /* We can canonicalize SIGN_EXTEND (op) as ZERO_EXTEND (op) when
+ we know the sign bit of OP must be clear. */
+ if (val_signbit_known_clear_p (GET_MODE (op),
+ nonzero_bits (op, GET_MODE (op))))
+ return simplify_gen_unary (ZERO_EXTEND, mode, op, GET_MODE (op));
+
+ /* (sign_extend:DI (subreg:SI (ctz:DI ...))) is (ctz:DI ...). */
+ if (GET_CODE (op) == SUBREG
+ && subreg_lowpart_p (op)
+ && GET_MODE (SUBREG_REG (op)) == mode
+ && is_a <scalar_int_mode> (mode, &int_mode)
+ && is_a <scalar_int_mode> (GET_MODE (op), &op_mode)
+ && GET_MODE_PRECISION (int_mode) <= HOST_BITS_PER_WIDE_INT
+ && GET_MODE_PRECISION (op_mode) < GET_MODE_PRECISION (int_mode)
+ && (nonzero_bits (SUBREG_REG (op), mode)
+ & ~(GET_MODE_MASK (op_mode) >> 1)) == 0)
+ return SUBREG_REG (op);
+
#if defined(POINTERS_EXTEND_UNSIGNED)
/* As we do not know which address space the pointer is referring to,
we can do this only if the target does not support different pointer
fixes the failure.
