Fix for PR c/57563

Hello Everyone,
	Attached, please find a patch that will fix the bug reported in PR 57563. There are a couple issues that went wrong. First, in the test case, we have a double multiplied to a double. When -std=c99 flag is used, they get converted to long double. The way to fix this is to add a type cast to the array notation to the same type as identity variable and thus they will all be double. 
	The second issue, was that a sec_reduce_mutating function takes in the address of a "mutating variable" (i.e. the variable that will hold the result), the array notation and a function pointer. For example, for the following code:

int a[10], x = 0;
void function_name (int *p, int r);
__sec_reduce_mutating (&x,  a[0:10], function_name);


__sec_reduce_mutating should be converted to:

for (ii =0; ii < 10; ii++)
	function_name (&x, a[ii]);

	In the test case I was not representing this correctly (as shown in the conversion above), but just computing the value that the function should do, thus making the test flaky. I made this fix in the test case. The other advantage of this change is that, in future I can change the what the function does (maybe with #defines and have multiple checks for different function body) and I don't have to change a lot of things.

I tried the patch on x86 and x86_64 and it works fine. I am assuming -m32 on x86_64 should have the same behavior as x86. So, is this OK for trunk?

Here are the Changelog entries:

gcc/c/ChangeLog
2013-06-08  Balaji V. Iyer  <balaji.v.iyer@intel.com>

        * c-array-notation.c (fix_builtin_array_notation_fn): Added a cast
        for all the usage of function parameter to match the identity var.

gcc/testsuite/ChangeLog
2013-06-08  Balaji V. Iyer  <balaji.v.iyer@intel.com>

        PR c/57563
        * c-c++-common/cilk-plus/AN/builtin_fn_mutating.c (main): Fixed a bug
        in how we check __sec_reduce_mutating function's result.

Thanks,

Balaji V. Iyer.

On Sun, 9 Jun 2013, Iyer, Balaji V wrote:

> 	Attached, please find a patch that will fix the bug reported in PR 
> 57563. There are a couple issues that went wrong. First, in the test 
> case, we have a double multiplied to a double. When -std=c99 flag is 
> used, they get converted to long double. The way to fix this is to add a 
> type cast to the array notation to the same type as identity variable 
> and thus they will all be double.

You don't say what the actual error was, and neither does the original PR.  
But if it was an ICE from an EXCESS_PRECISION_EXPR getting to the 
gimplifier, that suggests that c_fully_fold isn't getting called somewhere 
it should be - and probably calling c_fully_fold is the correct fix rather 
than inserting a cast.  If you can get such ICEs for 
EXCESS_PRECISION_EXPR, it's quite possible you might get them for 
C_MAYBE_CONST_EXPR as well (e.g. try using 0 / 0, or compound literals of 
variably modified type, in various places in the affected expressions), 
which should be fixed by using c_fully_fold but not by inserting a cast.

> -----Original Message-----
> From: Joseph Myers [mailto:joseph@codesourcery.com]
> Sent: Monday, June 10, 2013 10:40 AM
> To: Iyer, Balaji V
> Cc: gcc-patches@gcc.gnu.org; Jakub Jelinek; mpolacek@gcc.gnu.org
> Subject: Re: [PATCH] Fix for PR c/57563
> 
> On Sun, 9 Jun 2013, Iyer, Balaji V wrote:
> 
> > 	Attached, please find a patch that will fix the bug reported in PR
> > 57563. There are a couple issues that went wrong. First, in the test
> > case, we have a double multiplied to a double. When -std=c99 flag is
> > used, they get converted to long double. The way to fix this is to add
> > a type cast to the array notation to the same type as identity
> > variable and thus they will all be double.
> 
> You don't say what the actual error was, and neither does the original PR.
> But if it was an ICE from an EXCESS_PRECISION_EXPR getting to the gimplifier,
> that suggests that c_fully_fold isn't getting called somewhere it should be - and
> probably calling c_fully_fold is the correct fix rather than inserting a cast.  If you
> can get such ICEs for EXCESS_PRECISION_EXPR, it's quite possible you might get
> them for C_MAYBE_CONST_EXPR as well (e.g. try using 0 / 0, or compound
> literals of variably modified type, in various places in the affected expressions),
> which should be fixed by using c_fully_fold but not by inserting a cast.

It was not. It was actually a type mismatch between double and long double caught in verify_gimple_in_seq function.  So, is it OK for trunk?

Thanks,

Balaji V. Iyer.

> 
> --
> Joseph S. Myers
> joseph@codesourcery.com

On Mon, 10 Jun 2013, Iyer, Balaji V wrote:

> > You don't say what the actual error was, and neither does the original PR.
> > But if it was an ICE from an EXCESS_PRECISION_EXPR getting to the gimplifier,
> > that suggests that c_fully_fold isn't getting called somewhere it should be - and
> > probably calling c_fully_fold is the correct fix rather than inserting a cast.  If you
> > can get such ICEs for EXCESS_PRECISION_EXPR, it's quite possible you might get
> > them for C_MAYBE_CONST_EXPR as well (e.g. try using 0 / 0, or compound
> > literals of variably modified type, in various places in the affected expressions),
> > which should be fixed by using c_fully_fold but not by inserting a cast.
> 
> It was not. It was actually a type mismatch between double and long 
> double caught in verify_gimple_in_seq function.  So, is it OK for trunk?

A cast still doesn't make sense conceptually.  Could you give a more 
detailed analysis of what the trees look like at this point where you are 
inserting this cast, and how you get to a mismatch?

EXCESS_PRECISION_EXPR can be thought of as a conversion operator.  It 
should only appear at the top level of an expression.  At the point where 
excess precision should be removed - the value converted to its semantic 
type - either the expression with excess precision should be folded using 
c_fully_fold (if this is the expression of an expression statement, or 
otherwise will go inside a tree that c_fully_fold does not recurse 
inside), or the operand of the EXCESS_PRECISION_EXPR should be converted 
to the semantic type with the "convert" function.  In neither case is 
generating a cast appropriate; that's for when the user actually wrote a 
cast in their source code.