diff mbox

Incorrect code due to indirect tail call of varargs function with hard float ABI

Message ID 564A9327.8070607@linaro.org
State New
Headers show

Commit Message

Kugan Vivekanandarajah Nov. 17, 2015, 2:38 a.m. UTC 
On 17/11/15 12:00, Charles Baylis wrote:
> On 16 November 2015 at 22:24, Kugan <kugan.vivekanandarajah@linaro.org> wrote:

> 

>> Please note that we have a sibcall from "broken" to "indirect".

>>

>> "direct" is variadic function so it is conforming to AAPCS base standard.

>>

>> "broken" is a non-variadic function and will return the value in

>> floating point register for TARGET_HARD_FLOAT. Thus we should not be

>> doing sibcall here.

>>

>> Attached patch fixes this. Bootstrap and regression testing is ongoing.

>> Is this OK if no issues with the testing?

> 

> Hi Kugan,

> 

> It looks like this patch should work, but I think this is an overly

> conservative fix, as it prevents all sibcalls for hardfloat targets.

> It would be better if only variadic sibcalls were prevented on

> hardfloat. You can check for variadic calls by checking the

> function_type in the call expression (exp) using stdarg_p().

> 

> As an example to show how to test for variadic function calls, this is

> how to test it in gdb:

> 

> (gdb) b arm_function_ok_for_sibcall

> Breakpoint 1 at 0xdae59c: file

> /home/cbaylis/srcarea/gcc/gcc-git/gcc/config/arm/arm.c, line 6634.

> (gdb) r

> <snip>...

> Breakpoint 1, arm_function_ok_for_sibcall (decl=0x0, exp=0x7ffff6104ce8)

>     at /home/cbaylis/srcarea/gcc/gcc-git/gcc/config/arm/arm.c:6634

> 6634      if (cfun->machine->sibcall_blocked)

> (gdb) print debug_tree(exp)

>  <call_expr 0x7ffff6104ce8

>     type <real_type 0x7ffff62835e8 double sizes-gimplified DF

>         size <integer_cst 0x7ffff626cf18 constant 64>

>         unit size <integer_cst 0x7ffff626cf30 constant 8>

>         align 64 symtab 0 alias set -1 canonical type 0x7ffff62835e8

> precision 64

>         pointer_to_this <pointer_type 0x7ffff62837e0>>

>     side-effects addressable

>     fn <ssa_name 0x7ffff6275708

>         type <pointer_type 0x7ffff60e9540 type <function_type 0x7ffff60e9348>

> <snip>...

> (gdb) print stdarg_p((tree)0x7ffff60e9348)    <--- from function_type ^^^^^

> $2 = true

> 


How about:



Thanks,
Kugan
diff mbox

Patch

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index a379121..2376d66 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -6681,6 +6681,13 @@  arm_function_ok_for_sibcall (tree decl, tree exp)
         register.  */
       rtx a, b;

+      /* If it is an indirect function pointer, get the function type.  */
+      if (!decl
+         && POINTER_TYPE_P (TREE_TYPE (CALL_EXPR_FN (exp)))
+         && (TREE_CODE (TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp))))
+             == FUNCTION_TYPE))
+       decl = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp)));
+
       a = arm_function_value (TREE_TYPE (exp), decl, false);
       b = arm_function_value (TREE_TYPE (DECL_RESULT (cfun->decl)),
                              cfun->decl, false);