This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH] Missing TRULY_NOOP_TRUNCATION + remove comparison modes on MIPS
Eric Christopher writes:
> Sure. I always like to see the rtl there...
OK, I can do that.
Roger,
Would this still be OK to check in?
Thanks to both of you for the reviews.
Adam
Index: /home/anemet/src/gcc-3/src/gcc/combine.c
===================================================================
--- /home/anemet/src/gcc-3/src/gcc/combine.c (revision 109679)
+++ /home/anemet/src/gcc-3/src/gcc/combine.c (working copy)
@@ -10350,14 +10350,27 @@ simplify_comparison (enum rtx_code code,
/* If this AND operation is really a ZERO_EXTEND from a narrower
mode, the constant fits within that mode, and this is either an
equality or unsigned comparison, try to do this comparison in
- the narrower mode. */
+ the narrower mode.
+
+ Note that in:
+
+ (ne:DI (and:DI (reg:DI 4) (const_int 0xffffffff)) (const_int 0))
+ -> (ne:DI (reg:SI 4) (const_int 0))
+
+ unless TRULY_NOOP_TRUNCATION allows it or the register is
+ known to hold a value of the required mode the
+ transformation is invalid. */
if ((equality_comparison_p || unsigned_comparison_p)
&& GET_CODE (XEXP (op0, 1)) == CONST_INT
&& (i = exact_log2 ((INTVAL (XEXP (op0, 1))
& GET_MODE_MASK (mode))
+ 1)) >= 0
&& const_op >> i == 0
- && (tmode = mode_for_size (i, MODE_INT, 1)) != BLKmode)
+ && (tmode = mode_for_size (i, MODE_INT, 1)) != BLKmode
+ && (TRULY_NOOP_TRUNCATION (GET_MODE_BITSIZE (tmode),
+ GET_MODE_BITSIZE (GET_MODE (op0)))
+ || (REG_P (XEXP (op0, 0))
+ && reg_truncated_to_mode (tmode, XEXP (op0, 0)))))
{
op0 = gen_lowpart (tmode, XEXP (op0, 0));
continue;