[RFC][PATCH] Fix broken handling of LABEL_REF in genrecog + genpreds.

[Dominik Vogt <vogt@linux.vnet.ibm.com>]

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The attached patch fixes the handling of LABEL_REF in genrecog and
genpreds.

The current code assumes that X can have only a mode than PRED (X,
MODE) if X is CONST_INT, CONST_DOUBLE or CONST_WIDE_INT, but
actually that can be also the case for a LABEL_REF with VOIDmode.
Due to this it is necessary to add "const_int" (or similar) to
match_code of some predicates handling label_ref but not
const_int.

Ciao

Dominik ^_^  ^_^

-- 

Dominik Vogt
IBM Germany

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gcc/ChangeLog

	* config/s390/predicates.md ("larl_operand"): Remove now superfluous
	const_int and const_double.
	* genrecog.c (safe_predicate_mode): Return false for VOIDmode
	LABEL_REFs even if the predicate does not handle const_int,
	const_double or const_wide_int.
	* genpreds.c (add_mode_tests): Treat LABEL_REF like CONST_INT.

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From a211b6e3e2a64bdf47507c0e6151f137bcd4641f Mon Sep 17 00:00:00 2001
From: Dominik Vogt <vogt@linux.vnet.ibm.com>
Date: Fri, 11 Dec 2015 17:14:25 +0100
Subject: [PATCH] Fix broken handling of LABEL_REF in genrecog + genpreds.

The old code assumed that X can have only a mode than PRED (X, MODE) if X is
CONST_INT, CONST_DOUBLE or CONST_WIDE_INT, but actually that can be also the
case for LABEL_REF.  Due to this bug it was necessary to add "const_int" (or
similar) to match_code of some predicates handling label_ref but not const_int.
---
 gcc/config/s390/predicates.md | 5 +----
 gcc/genpreds.c                | 1 +
 gcc/genrecog.c                | 3 ++-
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/gcc/config/s390/predicates.md b/gcc/config/s390/predicates.md
index 5c462c4..f7ab836 100644
--- a/gcc/config/s390/predicates.md
+++ b/gcc/config/s390/predicates.md
@@ -121,10 +121,7 @@
 ;;  Return true if OP a valid operand for the LARL instruction.
 
 (define_predicate "larl_operand"
-; Note: Although CONST_INT and CONST_DOUBLE are not handled in this predicate,
-; at least one of them needs to appear or otherwise safe_predicate_mode will
-; assume that a VOIDmode LABEL_REF is not accepted either (see genrecog.c).
-  (match_code "label_ref, symbol_ref, const, const_int, const_double")
+  (match_code "label_ref, symbol_ref, const")
 {
   /* Allow labels and local symbols.  */
   if (GET_CODE (op) == LABEL_REF)
diff --git a/gcc/genpreds.c b/gcc/genpreds.c
index eac2180..3791f6d 100644
--- a/gcc/genpreds.c
+++ b/gcc/genpreds.c
@@ -320,6 +320,7 @@ add_mode_tests (struct pred_data *p)
 	{
 	case CONST_INT:
 	case CONST_WIDE_INT:
+	case LABEL_REF:
 	  matches_const_scalar_int_p = true;
 	  break;
 
diff --git a/gcc/genrecog.c b/gcc/genrecog.c
index 599121f..81ea35b 100644
--- a/gcc/genrecog.c
+++ b/gcc/genrecog.c
@@ -3382,7 +3382,8 @@ safe_predicate_mode (const struct pred_data *pred, machine_mode mode)
   if (GET_MODE_CLASS (mode) == MODE_INT
       && (pred->codes[CONST_INT]
 	  || pred->codes[CONST_DOUBLE]
-	  || pred->codes[CONST_WIDE_INT]))
+	  || pred->codes[CONST_WIDE_INT]
+	  || pred->codes[LABEL_REF]))
     return false;
 
   return !pred->special && mode != VOIDmode;
-- 
2.3.0