Hello All:

When using FlexiBLAS with OpenBLAS we noticed corruption of
the parameters passed to OpenBLAS functions. FlexiBLAS
basically provides a BLAS interface where each function
is a stub that forwards the arguments to a real BLAS lib,
like OpenBLAS.

Fixes the corruption of caller frame checking number of
arguments is less than equal to GP_ARG_NUM_REG (8)
excluding hidden unused DECLS.

Bootstrapped and regtested on powerpc64-linux-gnu.

Thanks & Regards
Ajit


rs6000: Stackoverflow in optimized code on PPC (PR100799)

When using FlexiBLAS with OpenBLAS we noticed corruption of
the parameters passed to OpenBLAS functions. FlexiBLAS
basically provides a BLAS interface where each function
is a stub that forwards the arguments to a real BLAS lib,
like OpenBLAS.

Fixes the corruption of caller frame checking number of
arguments is less than equal to GP_ARG_NUM_REG (8)
excluding hidden unused DECLS.

2024-03-22  Ajit Kumar Agarwal  <aagar...@linux.ibm.com>

gcc/ChangeLog:

        PR rtk-optimization/100799
        * config/rs600/rs600-calls.cc (rs6000_function_arg): Don't
        generate parameter save area if number of arguments passed
        less than equal to GP_ARG_NUM_REG (8) excluding hidden
        paramter.
        * function.cc (assign_parms_initialize_all): Check for hidden
        parameter in fortran code and set the flag hidden_string_length
        and actual paramter passed excluding hidden unused DECLS.
        * function.h: Add new field hidden_string_length and
        actual_parm_length in function structure.
---
 gcc/config/rs6000/rs6000-call.cc | 11 ++++++++++-
 gcc/function.cc                  | 26 ++++++++++++++++++++++++++
 gcc/function.h                   | 10 ++++++++++
 3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/gcc/config/rs6000/rs6000-call.cc b/gcc/config/rs6000/rs6000-call.cc
index 1f8f93a2ee7..8e6e3de6804 100644
--- a/gcc/config/rs6000/rs6000-call.cc
+++ b/gcc/config/rs6000/rs6000-call.cc
@@ -1857,7 +1857,16 @@ rs6000_function_arg (cumulative_args_t cum_v, const 
function_arg_info &arg)
 
          return rs6000_finish_function_arg (mode, rvec, k);
        }
-      else if (align_words < GP_ARG_NUM_REG)
+     /* Workaround buggy C/C++ wrappers around Fortran routines with
+       character(len=constant) arguments if the hidden string length arguments
+       are passed on the stack; if the callers forget to pass those arguments,
+       attempting to tail call in such routines leads to stack corruption.
+       Avoid return stack space for parameters <= 8 excluding hidden string
+       length argument is passed (partially or fully) on the stack in the
+       caller and the callee needs to pass any arguments on the stack.  */
+      else if (align_words < GP_ARG_NUM_REG
+              || (cfun->hidden_string_length
+              && cfun->actual_parm_length <= GP_ARG_NUM_REG))
        {
          if (TARGET_32BIT && TARGET_POWERPC64)
            return rs6000_mixed_function_arg (mode, type, align_words);
diff --git a/gcc/function.cc b/gcc/function.cc
index 3cef6c17bce..1318564b466 100644
--- a/gcc/function.cc
+++ b/gcc/function.cc
@@ -2326,6 +2326,32 @@ assign_parms_initialize_all (struct assign_parm_data_all 
*all)
 #endif
   all->args_so_far = pack_cumulative_args (&all->args_so_far_v);
 
+  unsigned int num_args = 0;
+  unsigned int hidden_length = 0;
+
+  /* Workaround buggy C/C++ wrappers around Fortran routines with
+     character(len=constant) arguments if the hidden string length arguments
+     are passed on the stack; if the callers forget to pass those arguments,
+     attempting to tail call in such routines leads to stack corruption.
+     Avoid return stack space for parameters <= 8 excluding hidden string
+     length argument is passed (partially or fully) on the stack in the
+     caller and the callee needs to pass any arguments on the stack.  */
+  for (tree arg = DECL_ARGUMENTS (current_function_decl);
+       arg; arg = DECL_CHAIN (arg))
+    {
+      num_args++;
+      if (DECL_HIDDEN_STRING_LENGTH (arg))
+       {
+         tree parmdef = ssa_default_def (cfun, arg);
+         if (parmdef == NULL || has_zero_uses (parmdef))
+           {
+             cfun->hidden_string_length = 1;
+             hidden_length++;
+           }
+       }
+   }
+
+  cfun->actual_parm_length = num_args - hidden_length;
 #ifdef INCOMING_REG_PARM_STACK_SPACE
   all->reg_parm_stack_space
     = INCOMING_REG_PARM_STACK_SPACE (current_function_decl);
diff --git a/gcc/function.h b/gcc/function.h
index 19e15bd63b0..5984f0007c2 100644
--- a/gcc/function.h
+++ b/gcc/function.h
@@ -346,6 +346,11 @@ struct GTY(()) function {
   /* Last assigned dependence info clique.  */
   unsigned short last_clique;
 
+  /* Actual parameter length ignoring hidden paramter.
+     This is done to C++ wrapper calling fortran module
+     which has hidden parameter that are not used.  */
+  unsigned int actual_parm_length;
+
   /* Collected bit flags.  */
 
   /* Number of units of general registers that need saving in stdarg
@@ -442,6 +447,11 @@ struct GTY(()) function {
   /* Set for artificial function created for [[assume (cond)]].
      These should be GIMPLE optimized, but not expanded to RTL.  */
   unsigned int assume_function : 1;
+
+  /* Hidden parameters while calling C++ wrapper to fortran
+     module. Set if there is hidden parameter in fortran
+     module while called C++ wrapper.  */
+  unsigned int hidden_string_length : 1;
 };
 
 /* Add the decl D to the local_decls list of FUN.  */
-- 
2.39.3

Reply via email to