genattrab.c generate switch

genattrab.c generate switch

[Jesper Broge Jørgensen]

Hello

genattrab.c can generate if statements that have very deep bracket 
nesting causing clang to produce errors (when target=arm-none-eabi) as 
explained at https://gcc.gnu.org/ml/gcc/2014-05/msg00032.html
At the above link it was suggested that genattrab.c generated a switch 
statement instead. I have made a patch that does just that.



gcc/ChangeLog:

2016-01-13  Jesper Broge Jørgensen  <jesperbroge@gmail.com>

     * genattrtab.c (check_attr_set_switch): implemented the function
     (write_attr_set): Check if expression can be written as a switch


diff --git a/gcc/genattrtab.c b/gcc/genattrtab.c
index 2caf8f6..b6de642 100644
--- a/gcc/genattrtab.c
+++ b/gcc/genattrtab.c
@@ -275,6 +275,8 @@ static bool attr_alt_subset_of_compl_p (rtx, rtx);
  static void clear_struct_flag      (rtx);
  static void write_attr_valueq       (FILE *, struct attr_desc *, const 
char *);
  static struct attr_value *find_most_used  (struct attr_desc *);
+static int check_attr_set_switch (FILE *outf, rtx exp,
+                    unsigned int attrs_cached, int write_cases, int 
indent);
  static void write_attr_set       (FILE *, struct attr_desc *, int, rtx,
                      const char *, const char *, rtx,
                      int, int, unsigned int);
@@ -4113,6 +4115,102 @@ eliminate_known_true (rtx known_true, rtx exp, 
int insn_code, int insn_index)
    return exp;
  }

+/* Check if exp contains a series of IOR conditions on the same attr_name.
+   If it does it can be turned into a switch statement and returns true.
+   If write_cases is true it will write the cases of the switch to 
outf.  */
+
+static int
+check_attr_set_switch (FILE *outf, rtx exp, unsigned int attrs_cached,
+                        int write_cases, int indent)
+{
+  if (GET_CODE (exp) != IOR)
+    return 0;
+  if (GET_CODE (XEXP (exp, 0)) != EQ_ATTR)
+    return 0;
+
+  rtx next = exp;
+  int ior_depth = 0;
+  int is_first = 1;
+
+  const char *attr_name_cmp = XSTR (XEXP (exp, 0), 0);
+
+  while (1)
+  {
+    rtx op1 = XEXP (next, 0);
+    rtx op2 = XEXP (next, 1);
+
+    if (GET_CODE (op1) != EQ_ATTR)
+      return 0;
+
+    const char *attr_name = XSTR (op1, 0);
+    const char *cmp_val = XSTR (op1, 1);
+
+    /* pointer compare is enough.  */
+    if (attr_name_cmp != attr_name)
+      return 0;
+
+    if (write_cases)
+    {
+      struct attr_desc *attr = find_attr (&attr_name, 0);
+      gcc_assert (attr);
+      if (is_first)
+      {
+        fprintf (outf, "(");
+        is_first = 0;
+        int i;
+        for (i = 0; i < cached_attr_count; i++)
+          if (attr->name == cached_attrs[i])
+            break;
+
+        if (i < cached_attr_count && (attrs_cached & (1U << i)) != 0)
+          fprintf (outf, "cached_%s", attr->name);
+        else if (i < cached_attr_count && (attrs_to_cache & (1U << i)) 
!= 0)
+          fprintf (outf, "(cached_%s = get_attr_%s (insn))", attr->name,
+                            attr->name);
+        else
+          fprintf (outf, "get_attr_%s (insn)", attr->name);
+        fprintf (outf, ")\n");
+        write_indent (outf, indent);
+        fprintf (outf, "{\n");
+      }
+      write_indent (outf, indent);
+      fprintf (outf, "case ");
+      write_attr_valueq (outf, attr, cmp_val);
+      fprintf (outf, ":\n");
+    }
+
+    const int code = GET_CODE (op2);
+    if (code != IOR)
+    {
+      if (code == EQ_ATTR)
+      {
+        const char *attr_name = XSTR (op2, 0);
+        const char *cmp_val = XSTR (op2, 1);
+
+        if (attr_name == alternative_name)
+          return 0;
+
+        struct attr_desc *attr = find_attr (&attr_name, 0);
+        gcc_assert (attr);
+
+        if (attr->is_const)
+          return 0;
+        else if (write_cases)
+        {
+          write_indent (outf, indent);
+          fprintf (outf, "case ");
+          write_attr_valueq (outf, attr, cmp_val);
+          fprintf (outf, ":\n");
+        }
+      }
+      break;
+    }
+    next = op2;
+    ior_depth++;
+  }
+  return ior_depth > 2;
+}
+
  /* Write out a series of tests and assignment statements to perform 
tests and
     sets of an attribute value.  We are passed an indentation amount 
and prefix
     and suffix strings to write around each attribute value (e.g., "return"
@@ -4123,6 +4221,7 @@ write_attr_set (FILE *outf, struct attr_desc 
*attr, int indent, rtx value,
          const char *prefix, const char *suffix, rtx known_true,
          int insn_code, int insn_index, unsigned int attrs_cached)
  {
+  int n_switches = 0;
    if (GET_CODE (value) == COND)
      {
        /* Assume the default value will be the default of the COND 
unless we
@@ -4132,6 +4231,7 @@ write_attr_set (FILE *outf, struct attr_desc 
*attr, int indent, rtx value,
        rtx newexp;
        int first_if = 1;
        int i;
+      int is_switch = 0;

        if (cached_attr_count)
      {
@@ -4176,40 +4276,68 @@ write_attr_set (FILE *outf, struct attr_desc 
*attr, int indent, rtx value,
        if (inner_true == false_rtx)
          continue;

+      is_switch = check_attr_set_switch (outf, testexp, attrs_cached, 0,
+          indent);
+
        attrs_cached_inside = attrs_cached;
        attrs_cached_after = attrs_cached;
        write_indent (outf, indent);
-      fprintf (outf, "%sif ", first_if ? "" : "else ");
-      first_if = 0;
-      write_test_expr (outf, testexp, attrs_cached,
-               (FLG_AFTER | FLG_INSIDE | FLG_OUTSIDE_AND));
-      attrs_cached = attrs_cached_after;
-      fprintf (outf, "\n");
-      write_indent (outf, indent + 2);
-      fprintf (outf, "{\n");
+      if (is_switch)
+        {
+          fprintf (outf, "switch ");
+          n_switches++;
+          first_if = 1;
+          check_attr_set_switch (outf, testexp, attrs_cached, 1, indent);
+          indent += 4;
+        }
+      else
+        {
+            fprintf (outf, "%sif ", first_if ? "" : "else ");
+            first_if = 0;
+            write_test_expr (outf, testexp, attrs_cached,
+                (FLG_AFTER | FLG_INSIDE | FLG_OUTSIDE_AND));
+                attrs_cached = attrs_cached_after;
+            fprintf (outf, "\n");
+        }
+        if (! is_switch)
+        {
+          write_indent (outf, indent + 2);
+          fprintf (outf, "{\n");
+        }
+

        write_attr_set (outf, attr, indent + 4,
                XVECEXP (value, 0, i + 1), prefix, suffix,
                inner_true, insn_code, insn_index,
                attrs_cached_inside);
        write_indent (outf, indent + 2);
-      fprintf (outf, "}\n");
+      if (is_switch)
+      {
+        fprintf (outf, "break;\n");
+        write_indent (outf, indent);
+        fprintf (outf, "default:\n");
+        indent += 4;
+      }
+      else
+        fprintf (outf, "}\n");
        our_known_true = newexp;
      }

-      if (! first_if)
+      if (! first_if && ! is_switch)
      {
        write_indent (outf, indent);
        fprintf (outf, "else\n");
        write_indent (outf, indent + 2);
        fprintf (outf, "{\n");
      }
+    else if (is_switch)
+        write_indent (outf, indent);

-      write_attr_set (outf, attr, first_if ? indent : indent + 4, 
default_val,
+      write_attr_set (outf, attr, (first_if || is_switch) ? indent : 
indent + 4, default_val,
                prefix, suffix, our_known_true, insn_code, insn_index,
                attrs_cached);

-      if (! first_if)
+      if (! first_if && ! is_switch)
      {
        write_indent (outf, indent + 2);
        fprintf (outf, "}\n");
@@ -4222,6 +4350,12 @@ write_attr_set (FILE *outf, struct attr_desc 
*attr, int indent, rtx value,
        write_attr_value (outf, attr, value);
        fprintf (outf, "%s\n", suffix);
      }
+    while (n_switches--)
+      {
+        indent -= 2;
+        write_indent (outf, indent);
+        fprintf (outf, "}\n");
+      }
  }

  /* Write a series of case statements for every instruction in list IE.

Re: genattrab.c generate switch

[Bernd Schmidt]

On 01/13/2016 01:53 AM, Jesper Broge Jørgensen wrote:
> genattrab.c can generate if statements that have very deep bracket
> nesting causing clang to produce errors (when target=arm-none-eabi) as
> explained at https://gcc.gnu.org/ml/gcc/2014-05/msg00032.html
> At the above link it was suggested that genattrab.c generated a switch
> statement instead. I have made a patch that does just that.

Some preliminaries first - I don't see your name in existing ChangeLogs; 
am I correct in assuming you've not gone through the copyright 
assignment process?

Secondly, we're currently in a development phase where we only accept 
bug fixes for gcc-6. You should resubmit/ping the patch once stage1 
opens again.

> 2016-01-13  Jesper Broge Jørgensen  <jesperbroge@gmail.com>
>
>      * genattrtab.c (check_attr_set_switch): implemented the function
>      (write_attr_set): Check if expression can be written as a switch

Please review our coding and documentation standards. ChangeLog entries 
should be complete sentences (or sometimes brief short-hands: the first 
one should just be "New function.")

> +static int check_attr_set_switch (FILE *outf, rtx exp,
> +                    unsigned int attrs_cached, int write_cases, int
> indent);

No reason to declare it if it is defined before its use.
> +  while (1)
> +  {

This and everything else here looks like it isn't following our 
indentation rules.


Bernd

Re: genattrab.c generate switch

[Jakub Jelinek]

On Mon, Jan 18, 2016 at 03:15:08PM +0100, Bernd Schmidt wrote:
> Secondly, we're currently in a development phase where we only accept bug
> fixes for gcc-6. You should resubmit/ping the patch once stage1 opens again.

I think this is a bug fix, it is a workaround for a broken compiler that
some people use as system compiler to bootstrap gcc.

	Jakub

Re: genattrab.c generate switch

[Jesper Broge Jørgensen]

On 18/01/16 15:15, Bernd Schmidt wrote:
> On 01/13/2016 01:53 AM, Jesper Broge Jørgensen wrote:
>> genattrab.c can generate if statements that have very deep bracket
>> nesting causing clang to produce errors (when target=arm-none-eabi) as
>> explained at https://gcc.gnu.org/ml/gcc/2014-05/msg00032.html
>> At the above link it was suggested that genattrab.c generated a switch
>> statement instead. I have made a patch that does just that.
>
> Some preliminaries first - I don't see your name in existing 
> ChangeLogs; am I correct in assuming you've not gone through the 
> copyright assignment process?
>
> Secondly, we're currently in a development phase where we only accept 
> bug fixes for gcc-6. You should resubmit/ping the patch once stage1 
> opens again.
>
>> 2016-01-13  Jesper Broge Jørgensen <jesperbroge@gmail.com>
>>
>>      * genattrtab.c (check_attr_set_switch): implemented the function
>>      (write_attr_set): Check if expression can be written as a switch
>
> Please review our coding and documentation standards. ChangeLog 
> entries should be complete sentences (or sometimes brief short-hands: 
> the first one should just be "New function.")
>
>> +static int check_attr_set_switch (FILE *outf, rtx exp,
>> +                    unsigned int attrs_cached, int write_cases, int
>> indent);
>
> No reason to declare it if it is defined before its use.
>> +  while (1)
>> +  {
>
> This and everything else here looks like it isn't following our 
> indentation rules.
>
>
> Bernd
No i have not gone through copyright assignment.
This is my first time trying to contribute to a GNU project so i have 
tried following the "Contributing to GCC" at 
https://gcc.gnu.org/contribute.html
There i followed the advice to run the patch through 
contrib/check_GNU_style.sh and it came out clean. Maybe 
contrib/check_GNU_style.sh does not check for indention rules and/or my 
editor is set up wrongly so it looked to me like i was following the 
coding standard.

I did not know you only accepted bug fixes though one could argue that 
this fixes a (style)bug in generated code.

Re: genattrab.c generate switch

[Manuel López-Ibáñez]

On 18/01/16 14:39, Jesper Broge Jørgensen wrote:
> No i have not gone through copyright assignment.
> This is my first time trying to contribute to a GNU project so i have tried
> following the "Contributing to GCC"@
> https://gcc.gnu.org/contribute.html
> There i followed the advice to run the patch through contrib/check_GNU_style.sh
> and it came out clean. Maybe contrib/check_GNU_style.sh does not check for
> indention rules and/or my editor is set up wrongly so it looked to me like i
> was following the coding standard.

Hi Jesper,

Unfortunately, https://gcc.gnu.org/contribute.html is quite hard to follow and 
outdated. I would suggest to start here: 
https://gcc.gnu.org/wiki/GettingStarted#Basics:_Contributing_to_GCC_in_10_easy_steps

 From there, you'll get to https://gcc.gnu.org/wiki/FormattingCodeForGCC

If you know how to improve those pages, for example extending them to other 
editors, I can give you write access.

Cheers,

Manuel.

Re: genattrab.c generate switch

[Jesper Broge Jørgensen]

On 18/01/16 18:39, Manuel López-Ibáñez wrote:
> On 18/01/16 14:39, Jesper Broge Jørgensen wrote:
>> No i have not gone through copyright assignment.
>> This is my first time trying to contribute to a GNU project so i have 
>> tried
>> following the "Contributing to GCC"@
>> https://gcc.gnu.org/contribute.html
>> There i followed the advice to run the patch through 
>> contrib/check_GNU_style.sh
>> and it came out clean. Maybe contrib/check_GNU_style.sh does not 
>> check for
>> indention rules and/or my editor is set up wrongly so it looked to me 
>> like i
>> was following the coding standard.
>
> Hi Jesper,
>
> Unfortunately, https://gcc.gnu.org/contribute.html is quite hard to 
> follow and outdated. I would suggest to start here: 
> https://gcc.gnu.org/wiki/GettingStarted#Basics:_Contributing_to_GCC_in_10_easy_steps
>
> From there, you'll get to https://gcc.gnu.org/wiki/FormattingCodeForGCC
>
> If you know how to improve those pages, for example extending them to 
> other editors, I can give you write access.
>
> Cheers,
>
> Manuel.
>
Hi

I found a formatting tool called uncrustify that comes with a gnu style 
config 
https://github.com/bengardner/uncrustify/blob/master/etc/gnu-indent.cfg 
that needed a few tweaks to format code that looked what is already in 
gcc/genattrtab.c

The tweaks was:

indent_with_tabs = 2 // instead of 0
sp_func_def_paren     = add // instead of remove
sp_func_proto_paren  = add // instead of remove
sp_func_call_paren     = add // instead of remove

So now the code should be correctly formatted.
Do i send in a new patch or just respond to the old one with the new 
changes?

I have also followed instructions at 
https://gcc.gnu.org/ml/gcc/2003-06/txt00010.txt to get copyright 
assignment though i have not yet received a reply.

Re: genattrab.c generate switch

[Bernd Schmidt]

On 01/18/2016 11:44 PM, Jesper Broge Jørgensen wrote:
> I found a formatting tool called uncrustify that comes with a gnu style
> config
> https://github.com/bengardner/uncrustify/blob/master/etc/gnu-indent.cfg
> that needed a few tweaks to format code that looked what is already in
> gcc/genattrtab.c
>
> The tweaks was:
>
> indent_with_tabs = 2 // instead of 0
> sp_func_def_paren     = add // instead of remove
> sp_func_proto_paren  = add // instead of remove
> sp_func_call_paren     = add // instead of remove
>
> So now the code should be correctly formatted.

Best to get that right when editing, though. emacs defaults to GNU style 
and other editors can also be tweaked.

> Do i send in a new patch or just respond to the old one with the new
> changes?

Usually best to send updated patches (as text/plain attachment to avoid 
word-wrapping and other whitespace damage).

> I have also followed instructions at
> https://gcc.gnu.org/ml/gcc/2003-06/txt00010.txt to get copyright
> assignment though i have not yet received a reply.

Ok, we'll have to wait for that.


Bernd

Re: genattrab.c generate switch

[Jesper Broge Jørgensen]

[-- Attachment #1: Type: text/plain, Size: 1387 bytes --]



On 19/01/16 13:18, Bernd Schmidt wrote:
> On 01/18/2016 11:44 PM, Jesper Broge Jørgensen wrote:
>> I found a formatting tool called uncrustify that comes with a gnu style
>> config
>> https://github.com/bengardner/uncrustify/blob/master/etc/gnu-indent.cfg
>> that needed a few tweaks to format code that looked what is already in
>> gcc/genattrtab.c
>>
>> The tweaks was:
>>
>> indent_with_tabs = 2 // instead of 0
>> sp_func_def_paren     = add // instead of remove
>> sp_func_proto_paren  = add // instead of remove
>> sp_func_call_paren     = add // instead of remove
>>
>> So now the code should be correctly formatted.
>
> Best to get that right when editing, though. emacs defaults to GNU 
> style and other editors can also be tweaked.
>
>> Do i send in a new patch or just respond to the old one with the new
>> changes?
>
> Usually best to send updated patches (as text/plain attachment to 
> avoid word-wrapping and other whitespace damage).
>
>> I have also followed instructions at
>> https://gcc.gnu.org/ml/gcc/2003-06/txt00010.txt to get copyright
>> assignment though i have not yet received a reply.
>
> Ok, we'll have to wait for that.
>
>
> Bernd
>
I have finally received the copyright assignment it is currently on its 
way over the atlantic via snail mail.
In the meantime i have attached the the refomatted patch here hoping it 
could be reviewed while we wait.

[-- Attachment #2: gcc_patch_reformatted.patch --]
[-- Type: text/plain, Size: 6503 bytes --]

gcc/ChangeLog:

2016-01-19  Jesper Broge Jørgensen  <jesperbroge@gmail.com>

	* genattrtab.c (check_attr_set_switch): New function
	(write_attr_set): Write a switch instead of if condition if possible


diff --git a/gcc/genattrtab.c b/gcc/genattrtab.c
index 2caf8f6..8e7f9e6 100644
--- a/gcc/genattrtab.c
+++ b/gcc/genattrtab.c
@@ -4113,6 +4113,103 @@ eliminate_known_true (rtx known_true, rtx exp, int insn_code, int insn_index)
   return exp;
 }
 
+/* Check if exp contains a series of IOR conditions on the same attr_name.
+   If it does it can be turned into a switch statement and returns true.
+   If write_cases is true it will write the cases of the switch to outf.  */
+
+static int
+check_attr_set_switch (FILE *outf, rtx exp, unsigned int attrs_cached,
+		       int write_cases, int indent)
+{
+  if (GET_CODE (exp) != IOR)
+    return 0;
+  if (GET_CODE (XEXP (exp, 0)) != EQ_ATTR)
+    return 0;
+
+  rtx next = exp;
+  int ior_depth = 0;
+  int is_first = 1;
+
+  const char *attr_name_cmp = XSTR (XEXP (exp, 0), 0);
+
+  while (1)
+    {
+      rtx op1 = XEXP (next, 0);
+      rtx op2 = XEXP (next, 1);
+
+      if (GET_CODE (op1) != EQ_ATTR)
+	return 0;
+
+      const char *attr_name = XSTR (op1, 0);
+      const char *cmp_val = XSTR (op1, 1);
+
+      /* pointer compare is enough.  */
+      if (attr_name_cmp != attr_name)
+	return 0;
+
+      if (write_cases)
+	{
+	  struct attr_desc *attr = find_attr (&attr_name, 0);
+	  gcc_assert (attr);
+	  if (is_first)
+	    {
+	      fprintf (outf, "(");
+	      is_first = 0;
+	      int i;
+	      for (i = 0; i < cached_attr_count; i++)
+		if (attr->name == cached_attrs[i])
+		  break;
+
+	      if (i < cached_attr_count && (attrs_cached & (1U << i)) != 0)
+		fprintf (outf, "cached_%s", attr->name);
+	      else if (i < cached_attr_count &&
+		       (attrs_to_cache & (1U << i)) != 0)
+		fprintf (outf, "(cached_%s = get_attr_%s (insn))", attr->name,
+			 attr->name);
+	      else
+		fprintf (outf, "get_attr_%s (insn)", attr->name);
+	      fprintf (outf, ")\n");
+	      write_indent (outf, indent);
+	      fprintf (outf, "{\n");
+	    }
+	  write_indent (outf, indent);
+	  fprintf (outf, "case ");
+	  write_attr_valueq (outf, attr, cmp_val);
+	  fprintf (outf, ":\n");
+	}
+
+      const int code = GET_CODE (op2);
+      if (code != IOR)
+	{
+	  if (code == EQ_ATTR)
+	    {
+	      const char *attr_name = XSTR (op2, 0);
+	      const char *cmp_val = XSTR (op2, 1);
+
+	      if (attr_name == alternative_name)
+		return 0;
+
+	      struct attr_desc *attr = find_attr (&attr_name, 0);
+	      gcc_assert (attr);
+
+	      if (attr->is_const)
+		return 0;
+	      else if (write_cases)
+		{
+		  write_indent (outf, indent);
+		  fprintf (outf, "case ");
+		  write_attr_valueq (outf, attr, cmp_val);
+		  fprintf (outf, ":\n");
+		}
+	    }
+	  break;
+	}
+      next = op2;
+      ior_depth++;
+    }
+  return ior_depth > 2;
+}
+
 /* Write out a series of tests and assignment statements to perform tests and
    sets of an attribute value.  We are passed an indentation amount and prefix
    and suffix strings to write around each attribute value (e.g., "return"
@@ -4123,6 +4220,7 @@ write_attr_set (FILE *outf, struct attr_desc *attr, int indent, rtx value,
 		const char *prefix, const char *suffix, rtx known_true,
 		int insn_code, int insn_index, unsigned int attrs_cached)
 {
+  int n_switches = 0;
   if (GET_CODE (value) == COND)
     {
       /* Assume the default value will be the default of the COND unless we
@@ -4132,6 +4230,7 @@ write_attr_set (FILE *outf, struct attr_desc *attr, int indent, rtx value,
       rtx newexp;
       int first_if = 1;
       int i;
+      int is_switch = 0;
 
       if (cached_attr_count)
 	{
@@ -4176,40 +4275,68 @@ write_attr_set (FILE *outf, struct attr_desc *attr, int indent, rtx value,
 	  if (inner_true == false_rtx)
 	    continue;
 
+	  is_switch = check_attr_set_switch (outf, testexp, attrs_cached, 0,
+					     indent);
+
 	  attrs_cached_inside = attrs_cached;
 	  attrs_cached_after = attrs_cached;
 	  write_indent (outf, indent);
-	  fprintf (outf, "%sif ", first_if ? "" : "else ");
-	  first_if = 0;
-	  write_test_expr (outf, testexp, attrs_cached,
-			   (FLG_AFTER | FLG_INSIDE | FLG_OUTSIDE_AND));
-	  attrs_cached = attrs_cached_after;
-	  fprintf (outf, "\n");
-	  write_indent (outf, indent + 2);
-	  fprintf (outf, "{\n");
+	  if (is_switch)
+	    {
+	      fprintf (outf, "switch ");
+	      n_switches++;
+	      first_if = 1;
+	      check_attr_set_switch (outf, testexp, attrs_cached, 1, indent);
+	      indent += 4;
+	    }
+	  else
+	    {
+	      fprintf (outf, "%sif ", first_if ? "" : "else ");
+	      first_if = 0;
+	      write_test_expr (outf, testexp, attrs_cached,
+			       (FLG_AFTER | FLG_INSIDE | FLG_OUTSIDE_AND));
+	      attrs_cached = attrs_cached_after;
+	      fprintf (outf, "\n");
+	    }
+	  if (!is_switch)
+	    {
+	      write_indent (outf, indent + 2);
+	      fprintf (outf, "{\n");
+	    }
+
 
 	  write_attr_set (outf, attr, indent + 4,
 			  XVECEXP (value, 0, i + 1), prefix, suffix,
 			  inner_true, insn_code, insn_index,
 			  attrs_cached_inside);
 	  write_indent (outf, indent + 2);
-	  fprintf (outf, "}\n");
+	  if (is_switch)
+	    {
+	      fprintf (outf, "break;\n");
+	      write_indent (outf, indent);
+	      fprintf (outf, "default:\n");
+	      indent += 4;
+	    }
+	  else
+	    fprintf (outf, "}\n");
 	  our_known_true = newexp;
 	}
 
-      if (! first_if)
+      if (! first_if && ! is_switch)
 	{
 	  write_indent (outf, indent);
 	  fprintf (outf, "else\n");
 	  write_indent (outf, indent + 2);
 	  fprintf (outf, "{\n");
 	}
+      else if (is_switch)
+	write_indent (outf, indent);
 
-      write_attr_set (outf, attr, first_if ? indent : indent + 4, default_val,
+      write_attr_set (outf, attr, (first_if || is_switch) ? indent : indent + 4, default_val,
 		      prefix, suffix, our_known_true, insn_code, insn_index,
 		      attrs_cached);
 
-      if (! first_if)
+      if (! first_if && ! is_switch)
 	{
 	  write_indent (outf, indent + 2);
 	  fprintf (outf, "}\n");
@@ -4222,6 +4349,12 @@ write_attr_set (FILE *outf, struct attr_desc *attr, int indent, rtx value,
       write_attr_value (outf, attr, value);
       fprintf (outf, "%s\n", suffix);
     }
+  while (n_switches--)
+    {
+      indent -= 2;
+      write_indent (outf, indent);
+      fprintf (outf, "}\n");
+    }
 }
 
 /* Write a series of case statements for every instruction in list IE.

Re: genattrab.c generate switch

[Patrick Palka]

On Tue, Jan 12, 2016 at 7:53 PM, Jesper Broge Jørgensen
<jesperbroge@gmail.com> wrote:
> Hello
>
> genattrab.c can generate if statements that have very deep bracket nesting
> causing clang to produce errors (when target=arm-none-eabi) as explained at
> https://gcc.gnu.org/ml/gcc/2014-05/msg00032.html
> At the above link it was suggested that genattrab.c generated a switch
> statement instead. I have made a patch that does just that.=

Have you considered first implementing the other suggestion in that
thread -- to avoid emitting the redundant parentheses in a consecutive
chain ||s and &&s? That kind of fix would be simpler and would fix the
compilation issue all the same, right?

Re: genattrab.c generate switch

[Jesper Broge Jørgensen]

On 01/02/16 20:19, Patrick Palka wrote:
> On Tue, Jan 12, 2016 at 7:53 PM, Jesper Broge Jørgensen
> <jesperbroge@gmail.com> wrote:
>> Hello
>>
>> genattrab.c can generate if statements that have very deep bracket nesting
>> causing clang to produce errors (when target=arm-none-eabi) as explained at
>> https://gcc.gnu.org/ml/gcc/2014-05/msg00032.html
>> At the above link it was suggested that genattrab.c generated a switch
>> statement instead. I have made a patch that does just that.=
> Have you considered first implementing the other suggestion in that
> thread -- to avoid emitting the redundant parentheses in a consecutive
> chain ||s and &&s? That kind of fix would be simpler and would fix the
> compilation issue all the same, right?
I think it makes more sense to have the special case logic as close to 
where you know that you have to handle it eg. in write_attr_set() 
instead of in the more general purpos write_test_expr() (which is the 
where the parentheses is inserted). Also creating a different flow 
control structure (writing a switch instead of an if statement) makes it 
clear that we are handling an edge case. Also most of the logic needed 
is in the new function check_attr_set_switch() that is used to check if 
the expression is indeed a chain of || operators which would have to be 
done either way, so not much simplification would be gained.
write_test_expr() also makes the promise (in form of an inline comment) 
that parentheses are inserted to avoid worrying about operator 
precedence, having a special case that does not insert parentheses would 
break that promise.
Lastly i would also guess that a switch statement could be better 
optimized by the compiler but one would have to inspect the assembly 
output which i have not done so that is guess-work.