This patch adds a new hook that gives the preferred alignment for a static rtx...

TARGET_STATIC_RTX_ALIGNMENT

This patch adds a new hook that gives the preferred alignment for
a static rtx, so that we don't need to query the front end in
force_const_mem.

2017-10-26  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* target.def (static_rtx_alignment): New hook.
	* targhooks.h (default_static_rtx_alignment): Declare.
	* targhooks.c (default_static_rtx_alignment): New function.
	* doc/tm.texi.in (TARGET_STATIC_RTX_ALIGNMENT): New hook.
	* doc/tm.texi: Regenerate.
	* varasm.c (force_const_mem): Use targetm.static_rtx_alignment
	instead of targetm.constant_alignment.  Remove call to
	set_mem_attributes.
	* config/cris/cris.c (TARGET_STATIC_RTX_ALIGNMENT): Redefine.
	(cris_preferred_mininum_alignment): New function, split out from...
	(cris_constant_alignment): ...here.
	(cris_static_rtx_alignment): New function.
	* config/i386/i386.c (ix86_static_rtx_alignment): New function,
	split out from...
	(ix86_constant_alignment): ...here.
	(TARGET_STATIC_RTX_ALIGNMENT): Redefine.
	* config/mmix/mmix.c (TARGET_STATIC_RTX_ALIGNMENT): Redefine.
	(mmix_static_rtx_alignment): New function.
	* config/spu/spu.c (spu_static_rtx_alignment): New function.
	(TARGET_STATIC_RTX_ALIGNMENT): Redefine.

From-SVN: r254102

11 files changed, 118 insertions, 15 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index ad54a57..3033a7f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,26 @@
+2017-10-26  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	* target.def (static_rtx_alignment): New hook.
+	* targhooks.h (default_static_rtx_alignment): Declare.
+	* targhooks.c (default_static_rtx_alignment): New function.
+	* doc/tm.texi.in (TARGET_STATIC_RTX_ALIGNMENT): New hook.
+	* doc/tm.texi: Regenerate.
+	* varasm.c (force_const_mem): Use targetm.static_rtx_alignment
+	instead of targetm.constant_alignment.  Remove call to
+	set_mem_attributes.
+	* config/cris/cris.c (TARGET_STATIC_RTX_ALIGNMENT): Redefine.
+	(cris_preferred_mininum_alignment): New function, split out from...
+	(cris_constant_alignment): ...here.
+	(cris_static_rtx_alignment): New function.
+	* config/i386/i386.c (ix86_static_rtx_alignment): New function,
+	split out from...
+	(ix86_constant_alignment): ...here.
+	(TARGET_STATIC_RTX_ALIGNMENT): Redefine.
+	* config/mmix/mmix.c (TARGET_STATIC_RTX_ALIGNMENT): Redefine.
+	(mmix_static_rtx_alignment): New function.
+	* config/spu/spu.c (spu_static_rtx_alignment): New function.
+	(TARGET_STATIC_RTX_ALIGNMENT): Redefine.
+
 2017-10-26  Tamar Christina  <tamar.christina@arm.com>
 
 	PR target/81800
diff --git a/gcc/config/cris/cris.c b/gcc/config/cris/cris.c
index fe80a27..8fa234f 100644
--- a/gcc/config/cris/cris.c
+++ b/gcc/config/cris/cris.c
@@ -165,6 +165,7 @@ static bool cris_function_value_regno_p (const unsigned int);
 static void cris_file_end (void);
 static unsigned int cris_hard_regno_nregs (unsigned int, machine_mode);
 static bool cris_hard_regno_mode_ok (unsigned int, machine_mode);
+static HOST_WIDE_INT cris_static_rtx_alignment (machine_mode);
 static HOST_WIDE_INT cris_constant_alignment (const_tree, HOST_WIDE_INT);
 
 /* This is the parsed result of the "-max-stack-stackframe=" option.  If
@@ -288,6 +289,8 @@ int cris_cpu_version = CRIS_DEFAULT_CPU_VERSION;
 #undef TARGET_HARD_REGNO_MODE_OK
 #define TARGET_HARD_REGNO_MODE_OK cris_hard_regno_mode_ok
 
+#undef TARGET_STATIC_RTX_ALIGNMENT
+#define TARGET_STATIC_RTX_ALIGNMENT cris_static_rtx_alignment
 #undef TARGET_CONSTANT_ALIGNMENT
 #define TARGET_CONSTANT_ALIGNMENT cris_constant_alignment
 
@@ -4329,6 +4332,26 @@ cris_hard_regno_mode_ok (unsigned int regno, machine_mode mode)
 	      || (regno != CRIS_MOF_REGNUM && regno != CRIS_ACR_REGNUM)));
 }
 
+/* Return the preferred minimum alignment for a static object.  */
+
+static HOST_WIDE_INT
+cris_preferred_mininum_alignment (void)
+{
+  if (!TARGET_CONST_ALIGN)
+    return 8;
+  if (TARGET_ALIGN_BY_32)
+    return 32;
+  return 16;
+}
+
+/* Implement TARGET_STATIC_RTX_ALIGNMENT.  */
+
+static HOST_WIDE_INT
+cris_static_rtx_alignment (machine_mode mode)
+{
+  return MAX (cris_preferred_mininum_alignment (), GET_MODE_ALIGNMENT (mode));
+}
+
 /* Implement TARGET_CONSTANT_ALIGNMENT.  Note that this hook has the
    effect of making gcc believe that ALL references to constant stuff
    (in code segment, like strings) have this alignment.  That is a rather
@@ -4339,11 +4362,7 @@ cris_hard_regno_mode_ok (unsigned int regno, machine_mode mode)
 static HOST_WIDE_INT
 cris_constant_alignment (const_tree, HOST_WIDE_INT basic_align)
 {
-  if (!TARGET_CONST_ALIGN)
-    return basic_align;
-  if (TARGET_ALIGN_BY_32)
-    return MAX (basic_align, 32);
-  return MAX (basic_align, 16);
+  return MAX (cris_preferred_mininum_alignment (), basic_align);
 }
 
 #if 0
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 56486e0..1facf12 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -28741,6 +28741,18 @@ ix86_sched_init_global (FILE *, int, int)
 }
 
 
+/* Implement TARGET_STATIC_RTX_ALIGNMENT.  */
+
+static HOST_WIDE_INT
+ix86_static_rtx_alignment (machine_mode mode)
+{
+  if (mode == DFmode)
+    return 64;
+  if (ALIGN_MODE_128 (mode))
+    return MAX (128, GET_MODE_ALIGNMENT (mode));
+  return GET_MODE_ALIGNMENT (mode);
+}
+
 /* Implement TARGET_CONSTANT_ALIGNMENT.  */
 
 static HOST_WIDE_INT
@@ -28749,10 +28761,9 @@ ix86_constant_alignment (const_tree exp, HOST_WIDE_INT align)
   if (TREE_CODE (exp) == REAL_CST || TREE_CODE (exp) == VECTOR_CST
       || TREE_CODE (exp) == INTEGER_CST)
     {
-      if (TYPE_MODE (TREE_TYPE (exp)) == DFmode && align < 64)
-	return 64;
-      else if (ALIGN_MODE_128 (TYPE_MODE (TREE_TYPE (exp))) && align < 128)
-	return 128;
+      machine_mode mode = TYPE_MODE (TREE_TYPE (exp));
+      HOST_WIDE_INT mode_align = ix86_static_rtx_alignment (mode);
+      return MAX (mode_align, align);
     }
   else if (!optimize_size && TREE_CODE (exp) == STRING_CST
 	   && TREE_STRING_LENGTH (exp) >= 31 && align < BITS_PER_WORD)
@@ -50295,6 +50306,8 @@ ix86_run_selftests (void)
 #undef TARGET_CAN_CHANGE_MODE_CLASS
 #define TARGET_CAN_CHANGE_MODE_CLASS ix86_can_change_mode_class
 
+#undef TARGET_STATIC_RTX_ALIGNMENT
+#define TARGET_STATIC_RTX_ALIGNMENT ix86_static_rtx_alignment
 #undef TARGET_CONSTANT_ALIGNMENT
 #define TARGET_CONSTANT_ALIGNMENT ix86_constant_alignment
 
diff --git a/gcc/config/mmix/mmix.c b/gcc/config/mmix/mmix.c
index e911594..4a73162 100644
--- a/gcc/config/mmix/mmix.c
+++ b/gcc/config/mmix/mmix.c
@@ -168,6 +168,7 @@ static void mmix_print_operand (FILE *, rtx, int);
 static void mmix_print_operand_address (FILE *, machine_mode, rtx);
 static bool mmix_print_operand_punct_valid_p (unsigned char);
 static void mmix_conditional_register_usage (void);
+static HOST_WIDE_INT mmix_static_rtx_alignment (machine_mode);
 static HOST_WIDE_INT mmix_constant_alignment (const_tree, HOST_WIDE_INT);
 static HOST_WIDE_INT mmix_starting_frame_offset (void);
 
@@ -284,6 +285,8 @@ static HOST_WIDE_INT mmix_starting_frame_offset (void);
 #undef TARGET_OPTION_OVERRIDE
 #define TARGET_OPTION_OVERRIDE mmix_option_override
 
+#undef TARGET_STATIC_RTX_ALIGNMENT
+#define TARGET_STATIC_RTX_ALIGNMENT mmix_static_rtx_alignment
 #undef TARGET_CONSTANT_ALIGNMENT
 #define TARGET_CONSTANT_ALIGNMENT mmix_constant_alignment
 
@@ -342,6 +345,14 @@ mmix_data_alignment (tree type ATTRIBUTE_UNUSED, int basic_align)
   return basic_align;
 }
 
+/* Implement TARGET_STATIC_RTX_ALIGNMENT.  */
+
+static HOST_WIDE_INT
+mmix_static_rtx_alignment (machine_mode mode)
+{
+  return MAX (GET_MODE_ALIGNMENT (mode), 32);
+}
+
 /* Implement tARGET_CONSTANT_ALIGNMENT.  */
 
 static HOST_WIDE_INT
diff --git a/gcc/config/spu/spu.c b/gcc/config/spu/spu.c
index eda7fca..bf21cca 100644
--- a/gcc/config/spu/spu.c
+++ b/gcc/config/spu/spu.c
@@ -7196,6 +7196,18 @@ spu_truly_noop_truncation (unsigned int outprec, unsigned int inprec)
   return inprec <= 32 && outprec <= inprec;
 }
 
+/* Implement TARGET_STATIC_RTX_ALIGNMENT.
+
+   Make all static objects 16-byte aligned.  This allows us to assume
+   they are also padded to 16 bytes, which means we can use a single
+   load or store instruction to access them.  */
+
+static HOST_WIDE_INT
+spu_static_rtx_alignment (machine_mode mode)
+{
+  return MAX (GET_MODE_ALIGNMENT (mode), 128);
+}
+
 /* Implement TARGET_CONSTANT_ALIGNMENT.
 
    Make all static objects 16-byte aligned.  This allows us to assume
@@ -7447,6 +7459,8 @@ static const struct attribute_spec spu_attribute_table[] =
 #undef TARGET_TRULY_NOOP_TRUNCATION
 #define TARGET_TRULY_NOOP_TRUNCATION spu_truly_noop_truncation
 
+#undef TARGET_STATIC_RTX_ALIGNMENT
+#define TARGET_STATIC_RTX_ALIGNMENT spu_static_rtx_alignment
 #undef TARGET_CONSTANT_ALIGNMENT
 #define TARGET_CONSTANT_ALIGNMENT spu_constant_alignment
 
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 8484c1d..c02f4d3 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -1078,6 +1078,13 @@ On 32-bit ELF the largest supported section alignment in bits is
 @samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts.
 @end defmac
 
+@deftypefn {Target Hook} HOST_WIDE_INT TARGET_STATIC_RTX_ALIGNMENT (machine_mode @var{mode})
+This hook returns the preferred alignment in bits for a
+statically-allocated rtx, such as a constant pool entry.  @var{mode}
+is the mode of the rtx.  The default implementation returns
+@samp{GET_MODE_ALIGNMENT (@var{mode})}.
+@end deftypefn
+
 @defmac DATA_ALIGNMENT (@var{type}, @var{basic-align})
 If defined, a C expression to compute the alignment for a variable in
 the static store.  @var{type} is the data type, and @var{basic-align} is
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 015f59e..37308e1 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -1026,6 +1026,8 @@ On 32-bit ELF the largest supported section alignment in bits is
 @samp{(0x80000000 * 8)}, but this is not representable on 32-bit hosts.
 @end defmac
 
+@hook TARGET_STATIC_RTX_ALIGNMENT
+
 @defmac DATA_ALIGNMENT (@var{type}, @var{basic-align})
 If defined, a C expression to compute the alignment for a variable in
 the static store.  @var{type} is the data type, and @var{basic-align} is
diff --git a/gcc/target.def b/gcc/target.def
index 435849c..6a1cd31 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -3336,6 +3336,15 @@ HOOK_VECTOR_END (addr_space)
 #define HOOK_PREFIX "TARGET_"
 
 DEFHOOK
+(static_rtx_alignment,
+ "This hook returns the preferred alignment in bits for a\n\
+statically-allocated rtx, such as a constant pool entry.  @var{mode}\n\
+is the mode of the rtx.  The default implementation returns\n\
+@samp{GET_MODE_ALIGNMENT (@var{mode})}.",
+ HOST_WIDE_INT, (machine_mode mode),
+ default_static_rtx_alignment)
+
+DEFHOOK
 (constant_alignment,
  "This hook returns the alignment in bits of a constant that is being\n\
 placed in memory.  @var{constant} is the constant and @var{basic_align}\n\
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 41cab38..92ecc90 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1173,6 +1173,14 @@ tree default_mangle_decl_assembler_name (tree decl ATTRIBUTE_UNUSED,
    return id;
 }
 
+/* The default implementation of TARGET_STATIC_RTX_ALIGNMENT.  */
+
+HOST_WIDE_INT
+default_static_rtx_alignment (machine_mode mode)
+{
+  return GET_MODE_ALIGNMENT (mode);
+}
+
 /* The default implementation of TARGET_CONSTANT_ALIGNMENT.  */
 
 HOST_WIDE_INT
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index 1510bb9..f60bca2 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -94,6 +94,7 @@ extern int default_builtin_vectorization_cost (enum vect_cost_for_stmt, tree, in
 
 extern tree default_builtin_reciprocal (tree);
 
+extern HOST_WIDE_INT default_static_rtx_alignment (machine_mode);
 extern HOST_WIDE_INT default_constant_alignment (const_tree, HOST_WIDE_INT);
 extern HOST_WIDE_INT constant_alignment_word_strings (const_tree,
 						      HOST_WIDE_INT);
diff --git a/gcc/varasm.c b/gcc/varasm.c
index d324ca03..a139151 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -3783,11 +3783,8 @@ force_const_mem (machine_mode mode, rtx x)
   *slot = desc;
 
   /* Align the location counter as required by EXP's data type.  */
-  align = GET_MODE_ALIGNMENT (mode == VOIDmode ? word_mode : mode);
-
-  tree type = lang_hooks.types.type_for_mode (mode, 0);
-  if (type != NULL_TREE)
-    align = targetm.constant_alignment (make_tree (type, x), align);
+  machine_mode align_mode = (mode == VOIDmode ? word_mode : mode);
+  align = targetm.static_rtx_alignment (align_mode);
 
   pool->offset += (align / BITS_PER_UNIT) - 1;
   pool->offset &= ~ ((align / BITS_PER_UNIT) - 1);
@@ -3829,7 +3826,6 @@ force_const_mem (machine_mode mode, rtx x)
 
   /* Construct the MEM.  */
   desc->mem = def = gen_const_mem (mode, symbol);
-  set_mem_attributes (def, lang_hooks.types.type_for_mode (mode, 0), 1);
   set_mem_align (def, align);
 
   /* If we're dropping a label to the constant pool, make sure we