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* [PING] PR middle-end/95126: Expand small const structs as immediate constants
@ 2022-05-21 10:49 Roger Sayle
  2022-06-05 17:53 ` Andreas Schwab
  0 siblings, 1 reply; 11+ messages in thread
From: Roger Sayle @ 2022-05-21 10:49 UTC (permalink / raw)
  To: gcc-patches

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I'd like to ping my patch for PR middle-end/95126 from February:
https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590949.html
As a regression fix, this has missed GCC 12, but hopefully its suitable
for 13 now we're back in stage1.

The patch has been refreshed and retested against gcc 13 trunk on
x86_64-pc-linux-gnu with make bootstrap and make -k check, both
with and without --target_board=unix{-m32} with no new failures.
Ok for mainline?

2022-05-21  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	PR middle-end/95126
	* calls.cc (load_register_parameters): When loading a suitable
	immediate_const_ctor_p VAR_DECL into a single word_mode register,
	construct it directly in a pseudo rather than read it (by parts)
	from memory.
	* expr.cc (int_expr_size): Make tree argument a const_tree.
	(immediate_const_ctor_p): Helper predicate.  Return true for
	simple constructors that may be materialized in a register.
	(expand_expr_real_1) [VAR_DECL]: When expanding a constant
	VAR_DECL with a suitable immediate_const_ctor_p constructor
	use store_constructor to materialize it directly in a pseudo.
	* expr.h (immediate_const_ctor_p): Prototype here.
	* varasm.cc (initializer_constant_valid_for_bitfield_p): Change
	VALUE argument from tree to const_tree.
	* varasm.h (initializer_constant_valid_for_bitfield_p): Update
	prototype.

gcc/testsuite/ChangeLog
	PR middle-end/95126
	* gcc.target/i386/pr95126-m32-1.c: New test case.
	* gcc.target/i386/pr95126-m32-2.c: New test case.
	* gcc.target/i386/pr95126-m32-3.c: New test case.
	* gcc.target/i386/pr95126-m32-4.c: New test case.
	* gcc.target/i386/pr95126-m64-1.c: New test case.
	* gcc.target/i386/pr95126-m64-2.c: New test case.
	* gcc.target/i386/pr95126-m64-3.c: New test case.
	* gcc.target/i386/pr95126-m64-4.c: New test case.


Thanks in advance,
Roger
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diff --git a/gcc/calls.cc b/gcc/calls.cc
index bbaf69c..a4336c1 100644
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -2095,7 +2095,8 @@ load_register_parameters (struct arg_data *args, int num_actuals,
 	  poly_int64 size = 0;
 	  HOST_WIDE_INT const_size = 0;
 	  rtx_insn *before_arg = get_last_insn ();
-	  tree type = TREE_TYPE (args[i].tree_value);
+	  tree tree_value = args[i].tree_value;
+	  tree type = TREE_TYPE (tree_value);
 	  if (RECORD_OR_UNION_TYPE_P (type) && TYPE_TRANSPARENT_AGGR (type))
 	    type = TREE_TYPE (first_field (type));
 	  /* Set non-negative if we must move a word at a time, even if
@@ -2172,6 +2173,24 @@ load_register_parameters (struct arg_data *args, int num_actuals,
 	      emit_move_insn (gen_rtx_REG (word_mode, REGNO (reg) + j),
 			      args[i].aligned_regs[j]);
 
+	  /* If we need a single register and the source is a constant
+	     VAR_DECL with a simple constructor, expand that constructor
+	     via a pseudo rather than read from (possibly misaligned)
+	     memory.  PR middle-end/95126.  */
+	  else if (nregs == 1
+		   && partial == 0
+		   && !args[i].pass_on_stack
+		   && VAR_P (tree_value)
+		   && TREE_READONLY (tree_value)
+		   && !TREE_SIDE_EFFECTS (tree_value)
+		   && immediate_const_ctor_p (DECL_INITIAL (tree_value)))
+	    {
+	      rtx target = gen_reg_rtx (word_mode);
+	      rtx x = expand_expr (DECL_INITIAL (tree_value),
+				   target, word_mode, EXPAND_NORMAL);
+	      reg = gen_rtx_REG (word_mode, REGNO (reg));
+	      emit_move_insn (reg, x);
+	    }
 	  else if (partial == 0 || args[i].pass_on_stack)
 	    {
 	      /* SIZE and CONST_SIZE are 0 for partial arguments and
diff --git a/gcc/expr.cc b/gcc/expr.cc
index 1806091..26f5528 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -100,7 +100,7 @@ static void do_tablejump (rtx, machine_mode, rtx, rtx, rtx,
 			  profile_probability);
 static rtx const_vector_from_tree (tree);
 static tree tree_expr_size (const_tree);
-static HOST_WIDE_INT int_expr_size (tree);
+static HOST_WIDE_INT int_expr_size (const_tree);
 static void convert_mode_scalar (rtx, rtx, int);
 
 \f
@@ -4867,7 +4867,22 @@ emit_push_insn (rtx x, machine_mode mode, tree type, rtx size,
 		    return false;
 		}
 	    }
-	  emit_block_move (target, xinner, size, BLOCK_OP_CALL_PARM);
+
+	  /* If source is a constant VAR_DECL with a simple constructor,
+             store the constructor to the stack instead of moving it.  */
+	  const_tree decl;
+	  if (partial == 0
+	      && MEM_P (xinner)
+	      && SYMBOL_REF_P (XEXP (xinner, 0))
+	      && (decl = SYMBOL_REF_DECL (XEXP (xinner, 0))) != NULL_TREE
+	      && VAR_P (decl)
+	      && TREE_READONLY (decl)
+	      && !TREE_SIDE_EFFECTS (decl)
+	      && immediate_const_ctor_p (DECL_INITIAL (decl), 2))
+	    store_constructor (DECL_INITIAL (decl), target, 0,
+			       int_expr_size (DECL_INITIAL (decl)), false);
+	  else
+	    emit_block_move (target, xinner, size, BLOCK_OP_CALL_PARM);
 	}
     }
   else if (partial > 0)
@@ -6576,6 +6591,25 @@ categorize_ctor_elements (const_tree ctor, HOST_WIDE_INT *p_nz_elts,
 				     p_init_elts, p_complete);
 }
 
+/* Return true if constructor CTOR is simple enough to be materialized
+   in an integer mode register.  Limit the size to WORDS words, which
+   is 1 by default.  */
+
+bool
+immediate_const_ctor_p (const_tree ctor, unsigned int words)
+{
+  /* Allow function to be called with a VAR_DECL's DECL_INITIAL.  */
+  if (!ctor || TREE_CODE (ctor) != CONSTRUCTOR)
+    return false;
+
+  return TREE_CONSTANT (ctor)
+	 && !TREE_ADDRESSABLE (ctor)
+	 && CONSTRUCTOR_NELTS (ctor)
+	 && TREE_CODE (TREE_TYPE (ctor)) != ARRAY_TYPE
+	 && int_expr_size (ctor) <= words * UNITS_PER_WORD
+	 && initializer_constant_valid_for_bitfield_p (ctor);
+}
+
 /* TYPE is initialized by a constructor with NUM_ELTS elements, the last
    of which had type LAST_TYPE.  Each element was itself a complete
    initializer, in the sense that every meaningful byte was explicitly
@@ -10535,6 +10569,21 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
 	  if (temp)
 	    return temp;
 	}
+      /* Expand const VAR_DECLs with CONSTRUCTOR initializers that
+	 have scalar integer modes to a reg via store_constructor.  */
+      if (TREE_READONLY (exp)
+	  && !TREE_SIDE_EFFECTS (exp)
+	  && (modifier == EXPAND_NORMAL || modifier == EXPAND_STACK_PARM)
+	  && immediate_const_ctor_p (DECL_INITIAL (exp))
+	  && SCALAR_INT_MODE_P (TYPE_MODE (TREE_TYPE (exp)))
+	  && crtl->emit.regno_pointer_align_length
+	  && !target)
+	{
+	  target = gen_reg_rtx (TYPE_MODE (TREE_TYPE (exp)));
+	  store_constructor (DECL_INITIAL (exp), target, 0,
+			     int_expr_size (DECL_INITIAL (exp)), false);
+	  return target;
+	}
       /* ... fall through ...  */
 
     case PARM_DECL:
@@ -13129,7 +13178,7 @@ expr_size (tree exp)
    if the size can vary or is larger than an integer.  */
 
 static HOST_WIDE_INT
-int_expr_size (tree exp)
+int_expr_size (const_tree exp)
 {
   tree size;
 
diff --git a/gcc/expr.h b/gcc/expr.h
index 7e5cf49..d777c28 100644
--- a/gcc/expr.h
+++ b/gcc/expr.h
@@ -338,6 +338,7 @@ extern unsigned HOST_WIDE_INT highest_pow2_factor (const_tree);
 extern bool categorize_ctor_elements (const_tree, HOST_WIDE_INT *,
 				      HOST_WIDE_INT *, HOST_WIDE_INT *,
 				      bool *);
+extern bool immediate_const_ctor_p (const_tree, unsigned int words = 1);
 
 extern void expand_operands (tree, tree, rtx, rtx*, rtx*,
 			     enum expand_modifier);
diff --git a/gcc/varasm.cc b/gcc/varasm.cc
index 6454f1c..826a9ca 100644
--- a/gcc/varasm.cc
+++ b/gcc/varasm.cc
@@ -5069,7 +5069,7 @@ initializer_constant_valid_p (tree value, tree endtype, bool reverse)
    an element of a "constant" initializer.  */
 
 bool
-initializer_constant_valid_for_bitfield_p (tree value)
+initializer_constant_valid_for_bitfield_p (const_tree value)
 {
   /* For bitfields we support integer constants or possibly nested aggregates
      of such.  */
@@ -5078,7 +5078,7 @@ initializer_constant_valid_for_bitfield_p (tree value)
     case CONSTRUCTOR:
       {
 	unsigned HOST_WIDE_INT idx;
-	tree elt;
+	const_tree elt;
 
 	FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (value), idx, elt)
 	  if (!initializer_constant_valid_for_bitfield_p (elt))
diff --git a/gcc/varasm.h b/gcc/varasm.h
index 8ba8374..acbd9fa 100644
--- a/gcc/varasm.h
+++ b/gcc/varasm.h
@@ -65,7 +65,7 @@ extern tree initializer_constant_valid_p (tree, tree, bool = false);
 /* Return true if VALUE is a valid constant-valued expression
    for use in initializing a static bit-field; one that can be
    an element of a "constant" initializer.  */
-extern bool initializer_constant_valid_for_bitfield_p (tree);
+extern bool initializer_constant_valid_for_bitfield_p (const_tree);
 
 /* Whether a constructor CTOR is a valid static constant initializer if all
    its elements are.  This used to be internal to initializer_constant_valid_p
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m32-1.c b/gcc/testsuite/gcc.target/i386/pr95126-m32-1.c
new file mode 100644
index 0000000..1d6acd6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m32-1.c
@@ -0,0 +1,16 @@
+/* { dg-do compile { target { ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a,b; signed char c; };
+
+void call_func(void)
+{
+    extern int func(struct small X);
+    static struct small const s = { 1,2,0 };
+    func(s);
+}
+
+/* { dg-final { scan-assembler "movl\[ \\t]*\\\$" } } */
+/* { dg-final { scan-assembler "movb\[ \\t]*\\\$0, " } } */
+/* { dg-final { scan-assembler-not "movzwl" } } */
+
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m32-2.c b/gcc/testsuite/gcc.target/i386/pr95126-m32-2.c
new file mode 100644
index 0000000..b46be9d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m32-2.c
@@ -0,0 +1,16 @@
+/* { dg-do compile { target { ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a,b; signed char c; };
+static const struct small s = { 1,2,0 };
+extern int func(struct small X);
+
+void call_func(void)
+{
+  func(s);
+}
+
+/* { dg-final { scan-assembler "movl\[ \\t]*\\\$" } } */
+/* { dg-final { scan-assembler "movb\[ \\t]*\\\$0, " } } */
+/* { dg-final { scan-assembler-not "movzwl" } } */
+
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m32-3.c b/gcc/testsuite/gcc.target/i386/pr95126-m32-3.c
new file mode 100644
index 0000000..cc2fe94
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m32-3.c
@@ -0,0 +1,15 @@
+/* { dg-do compile { target { ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a; };
+
+void call_func(void)
+{
+    extern int func(struct small X);
+    static struct small const s = { 2 };
+    func(s);
+}
+
+/* { dg-final { scan-assembler "pushl\[ \\t]*\\\$2" } } */
+/* { dg-final { scan-assembler-not "movzwl" } } */
+
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m32-4.c b/gcc/testsuite/gcc.target/i386/pr95126-m32-4.c
new file mode 100644
index 0000000..e829335
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m32-4.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target { ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a,b; };
+
+void call_func(void)
+{
+    extern int func(struct small X);
+    static struct small const s = { 1,2 };
+    func(s);
+}
+
+/* { dg-final { scan-assembler "pushl\[ \\t]*\\\$131073" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m64-1.c b/gcc/testsuite/gcc.target/i386/pr95126-m64-1.c
new file mode 100644
index 0000000..d5c6dded
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m64-1.c
@@ -0,0 +1,17 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a,b; signed char c; };
+
+void call_func(void)
+{
+    extern int func(struct small X);
+    static struct small const s = { 1,2,0 };
+    func(s);
+}
+
+/* { dg-final { scan-assembler "movl\[ \\t]*\\\$131073, " } } */
+/* { dg-final { scan-assembler-not "movzwl" } } */
+/* { dg-final { scan-assembler-not "salq" } } */
+/* { dg-final { scan-assembler-not "orq" } } */
+
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m64-2.c b/gcc/testsuite/gcc.target/i386/pr95126-m64-2.c
new file mode 100644
index 0000000..0230ffc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m64-2.c
@@ -0,0 +1,17 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a,b; signed char c; };
+static const struct small s = { 1,2,0 };
+extern int func(struct small X);
+
+void call_func(void)
+{
+  func(s);
+}
+
+/* { dg-final { scan-assembler "movl\[ \\t]*\\\$131073, " } } */
+/* { dg-final { scan-assembler-not "movzwl" } } */
+/* { dg-final { scan-assembler-not "salq" } } */
+/* { dg-final { scan-assembler-not "orq" } } */
+
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m64-3.c b/gcc/testsuite/gcc.target/i386/pr95126-m64-3.c
new file mode 100644
index 0000000..25afe3a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m64-3.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a; };
+
+void call_func(void)
+{
+    extern int func(struct small X);
+    static struct small const s = { 2 };
+    func(s);
+}
+
+/* { dg-final { scan-assembler "movl\[ \\t]*\\\$2, " } } */
+/* { dg-final { scan-assembler-not "movzwl" } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr95126-m64-4.c b/gcc/testsuite/gcc.target/i386/pr95126-m64-4.c
new file mode 100644
index 0000000..71c7908
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr95126-m64-4.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2" } */
+
+struct small{ short a,b; };
+
+void call_func(void)
+{
+    extern int func(struct small X);
+    static struct small const s = { 1,2 };
+    func(s);
+}
+
+/* { dg-final { scan-assembler "movl\[ \\t]*\\\$131073, " } } */

^ permalink raw reply	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2022-06-06 15:52 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-05-21 10:49 [PING] PR middle-end/95126: Expand small const structs as immediate constants Roger Sayle
2022-06-05 17:53 ` Andreas Schwab
2022-06-05 20:31   ` Rainer Orth
2022-06-06  8:43     ` Roger Sayle
2022-06-06 11:16       ` Andreas Schwab
2022-06-06 11:23         ` Roger Sayle
2022-06-06 11:44           ` Andreas Schwab
2022-06-06 12:01         ` Rainer Orth
2022-06-06 12:00       ` Rainer Orth
2022-06-06 12:29         ` Roger Sayle
2022-06-06 15:52           ` Rainer Orth

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