xtensa: Defer storing integer constants into litpool until reload

Storing integer constants into litpool in the early stage of compilation
hinders some integer optimizations.  In fact, such integer constants are
not subject to the constant folding process.

For example:

    extern unsigned short value;
    extern void foo(void);
    void test(void) {
      if (value == 30001)
        foo();
    }

	.literal_position
	.literal .LC0, value
	.literal .LC1, 30001
    test:
	l32r	a3, .LC0
	l32r	a2, .LC1
	l16ui	a3, a3, 0
	extui	a2, a2, 0, 16  // runtime zero-extension despite constant
	bne	a3, a2, .L1
	j.l	foo, a9
    .L1:
	ret.n

This patch defers the placement of integer constants into litpool until
the start of reload:

	.literal_position
	.literal .LC0, value
	.literal .LC1, 30001
    test:
	l32r	a3, .LC0
	l32r	a2, .LC1
	l16ui	a3, a3, 0
	bne	a3, a2, .L1
	j.l	foo, a9
    .L1:
	ret.n

gcc/ChangeLog:

	* config/xtensa/constraints.md (Y):
	Change to include integer constants until reload begins.
	* config/xtensa/predicates.md (move_operand): Ditto.
	* config/xtensa/xtensa.cc (xtensa_emit_move_sequence):
	Change to allow storing integer constants into litpool only after
	reload begins.

diff --git a/gcc/config/xtensa/constraints.md b/gcc/config/xtensa/constraints.md
index e7ac8dbfebf8a82b875fd7d497a8d6619a583832..0b7dcd1440e716d59fb1ca2231c10717e84964e9 100644 (file)
--- a/gcc/config/xtensa/constraints.md
+++ b/gcc/config/xtensa/constraints.md
@@ -113,8 +113,10 @@
 
 (define_constraint "Y"
  "A constant that can be used in relaxed MOVI instructions."
- (and (match_code "const_int,const_double,const,symbol_ref,label_ref")
-      (match_test "TARGET_AUTO_LITPOOLS")))
+ (ior (and (match_code "const_int,const_double,const,symbol_ref,label_ref")
+          (match_test "TARGET_AUTO_LITPOOLS"))
+      (and (match_code "const_int")
+          (match_test "can_create_pseudo_p ()"))))
 
 ;; Memory constraints.  Do not use define_memory_constraint here.  Doing so
 ;; causes reload to force some constants into the constant pool, but since

diff --git a/gcc/config/xtensa/predicates.md b/gcc/config/xtensa/predicates.md
index edd13ae41b96ab3d57abfdfe6bdbbda276250ad2..0590c0f81a99c616eaf19bbe28aa9ca47ebe158f 100644 (file)
--- a/gcc/config/xtensa/predicates.md
+++ b/gcc/config/xtensa/predicates.md
@@ -147,8 +147,9 @@
               (match_test "!constantpool_mem_p (op)
                            || GET_MODE_SIZE (mode) % UNITS_PER_WORD == 0")))
      (ior (and (match_code "const_int")
-              (match_test "GET_MODE_CLASS (mode) == MODE_INT
-                           && xtensa_simm12b (INTVAL (op))"))
+              (match_test "(GET_MODE_CLASS (mode) == MODE_INT
+                            && xtensa_simm12b (INTVAL (op)))
+                           || can_create_pseudo_p ()"))
          (and (match_code "const_int,const_double,const,symbol_ref,label_ref")
               (match_test "(TARGET_CONST16 || TARGET_AUTO_LITPOOLS)
                            && CONSTANT_P (op)

diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index d6f08b11648ca79008d815afd89f193585516558..c5d00acdf2cb2e3905a7f14bffc5c0fc2ae4d179 100644 (file)
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -1182,7 +1182,8 @@ xtensa_emit_move_sequence (rtx *operands, machine_mode mode)
          return 1;
        }
 
-      if (! TARGET_AUTO_LITPOOLS && ! TARGET_CONST16)
+      if (! TARGET_AUTO_LITPOOLS && ! TARGET_CONST16
+         && ! (CONST_INT_P (src) && can_create_pseudo_p ()))
        {
          src = force_const_mem (SImode, src);
          operands[1] = src;