===================================================================
@@ -1316,10 +1316,16 @@ forward_propagate_and_simplify (df_ref u
separately try plugging the definition in the note and simplifying.
And only install a REQ_EQUAL note when the destination is a REG
that isn't mentioned in USE_SET, as the note would be invalid
- otherwise. */
- set_reg_equal = (note == NULL_RTX && REG_P (SET_DEST (use_set))
- && ! reg_mentioned_p (SET_DEST (use_set),
- SET_SRC (use_set)));
+ otherwise. We also don't want to install a note if we are merely
+ propagating a pseudo since verifying that this pseudo isn't dead
+ is a pain; moreover such a note won't help anything. */
+ set_reg_equal = (note == NULL_RTX
+ && REG_P (SET_DEST (use_set))
+ && !REG_P (src)
+ && !(GET_CODE (src) == SUBREG
+ && REG_P (SUBREG_REG (src)))
+ && !reg_mentioned_p (SET_DEST (use_set),
+ SET_SRC (use_set)));
}
if (GET_MODE (*loc) == VOIDmode)
===================================================================
@@ -5311,33 +5311,33 @@ cse_insn (rtx insn)
}
/* If this is a single SET, we are setting a register, and we have an
- equivalent constant, we want to add a REG_NOTE. We don't want
- to write a REG_EQUAL note for a constant pseudo since verifying that
- that pseudo hasn't been eliminated is a pain. Such a note also
- won't help anything.
+ equivalent constant, we want to add a REG_EQUAL note if the constant
+ is different from the source. We don't want to do it for a constant
+ pseudo since verifying that this pseudo hasn't been eliminated is a
+ pain; moreover such a note won't help anything.
Avoid a REG_EQUAL note for (CONST (MINUS (LABEL_REF) (LABEL_REF)))
which can be created for a reference to a compile time computable
entry in a jump table. */
-
- if (n_sets == 1 && src_const && REG_P (dest)
+ if (n_sets == 1
+ && REG_P (dest)
+ && src_const
&& !REG_P (src_const)
- && ! (GET_CODE (src_const) == CONST
- && GET_CODE (XEXP (src_const, 0)) == MINUS
- && GET_CODE (XEXP (XEXP (src_const, 0), 0)) == LABEL_REF
- && GET_CODE (XEXP (XEXP (src_const, 0), 1)) == LABEL_REF))
+ && !(GET_CODE (src_const) == SUBREG
+ && REG_P (SUBREG_REG (src_const)))
+ && !(GET_CODE (src_const) == CONST
+ && GET_CODE (XEXP (src_const, 0)) == MINUS
+ && GET_CODE (XEXP (XEXP (src_const, 0), 0)) == LABEL_REF
+ && GET_CODE (XEXP (XEXP (src_const, 0), 1)) == LABEL_REF)
+ && !rtx_equal_p (src, src_const))
{
- /* We only want a REG_EQUAL note if src_const != src. */
- if (! rtx_equal_p (src, src_const))
- {
- /* Make sure that the rtx is not shared. */
- src_const = copy_rtx (src_const);
+ /* Make sure that the rtx is not shared. */
+ src_const = copy_rtx (src_const);
- /* Record the actual constant value in a REG_EQUAL note,
- making a new one if one does not already exist. */
- set_unique_reg_note (insn, REG_EQUAL, src_const);
- df_notes_rescan (insn);
- }
+ /* Record the actual constant value in a REG_EQUAL note,
+ making a new one if one does not already exist. */
+ set_unique_reg_note (insn, REG_EQUAL, src_const);
+ df_notes_rescan (insn);
}
/* Now deal with the destination. */
This is the miscompilation of the Ada front-end (ureal.adb) on x86-64/Linux with profiled bootstrap and another instance of the infamous webizer bug, whereby a REG_EQUAL note for a dead pseudo-register ends up creating an insn that wrongly zeroes another pseudo-register. The origin is fwprop1: from (insn 399 205 400 13 (set (reg:DI 282 [ ln ]) (subreg:DI (reg:TI 189) 0)) /home/eric/svn/gcc/gcc/ada/urealp.adb:622 87 {*movdi_internal_rex64} (nil)) (insn 400 399 208 13 (set (reg:DI 283 [ ln+8 ]) (subreg:DI (reg:TI 189) 8)) /home/eric/svn/gcc/gcc/ada/urealp.adb:622 87 {*movdi_internal_rex64} (expr_list:REG_DEAD (reg:TI 189) the pass tries to forward-propagate (subreg:DI (reg:TI 189) 0)) into a bunch of insns, which almost always fails and thus generates the much dreaded REG_EQUAL notes: In insn 208, replacing (subreg:SI (reg:DI 282 [ ln ]) 0) with (subreg:SI (reg:TI 189) 0) Changes to insn 208 not profitable Setting REG_EQUAL note In insn 210, replacing (lshiftrt:DI (reg:DI 282 [ ln ]) (const_int 32 [0x20])) with (lshiftrt:DI (subreg:DI (reg:TI 189) 0) (const_int 32 [0x20])) Changes to insn 210 not profitable Setting REG_EQUAL note In insn 252, replacing (lshiftrt:DI (reg:DI 283 [ ln+8 ]) (const_int 32 [0x20])) with (lshiftrt:DI (subreg:DI (reg:TI 189) 8) (const_int 32 [0x20])) Changes to insn 252 not profitable Setting REG_EQUAL note In insn 257, replacing (subreg:SI (reg:DI 282 [ ln ]) 0) with (subreg:SI (reg:TI 189) 0) Changes to insn 257 not profitable Setting REG_EQUAL note I think there is no point in creating a REG_EQUAL note when you're trying to propagate a pseudo (or a subreg of a pseudo here). As a matter of fact, that's what CSE explicitly does not: /* If this is a single SET, we are setting a register, and we have an equivalent constant, we want to add a REG_NOTE. We don't want to write a REG_EQUAL note for a constant pseudo since verifying that that pseudo hasn't been eliminated is a pain. Such a note also won't help anything. Avoid a REG_EQUAL note for (CONST (MINUS (LABEL_REF) (LABEL_REF))) which can be created for a reference to a compile time computable entry in a jump table. */ if (n_sets == 1 && src_const && REG_P (dest) && !REG_P (src_const) so we should not do it in fwprop either. Patch attached (which adds the SUBREG case to cse.c as well); it introduces no changes at -O2 for the testcases in gcc.c-torture/compile. Tested on x86-64/Linux. Thoughts? 2013-02-06 Eric Botcazou <ebotcazou@adacore.com> PR rtl-optimization/56178 * cse.c (cse_insn): Do not create a REG_EQUAL note if the source is a SUBREG of a register. Tidy up related block of code. * fwprop.c (orward_propagate_and_simplify): Do not create a REG_EQUAL note if the source is a register or a SUBREG of a register.