[Patch, GCC/ARM, gcc-5-branch] Fix PR68390 Incorrect code due to indirect tail call of varargs function with hard float ABI

[Christophe Lyon]

Hi,

It looks like we forgot to backport the fix for PR68390 to gcc-5-branch.
The patch applies cleanly, and fwiw we've had it in the linaro-5
branch for a while.

OK to apply to gcc-5-branch?

Thanks,

Christophe

2017-04-12  Christophe Lyon  <christophe.l...@linaro.org>

        Backport from mainline
        +2015-11-23  Kugan Vivekanandarajah  <kug...@linaro.org>

        gcc/
        PR target/68390
        * config/arm/arm.c (arm_function_ok_for_sibcall): Get function type
        for indirect function call.

        gcc/testsuite/
        PR target/68390
        * gcc.c-torture/execute/pr68390.c: New test.


Index: gcc/config/arm/arm.c
===================================================================
--- gcc/config/arm/arm.c        (revision 246880)
+++ gcc/config/arm/arm.c        (working copy)
@@ -6507,8 +6507,13 @@
         a VFP register but then need to transfer it to a core
         register.  */
       rtx a, b;
+      tree decl_or_type = decl;
 
-      a = arm_function_value (TREE_TYPE (exp), decl, false);
+      /* If it is an indirect function pointer, get the function type.  */
+      if (!decl)
+       decl_or_type = TREE_TYPE (TREE_TYPE (CALL_EXPR_FN (exp)));
+
+      a = arm_function_value (TREE_TYPE (exp), decl_or_type, false);
       b = arm_function_value (TREE_TYPE (DECL_RESULT (cfun->decl)),
                              cfun->decl, false);
       if (!rtx_equal_p (a, b))
Index: gcc/testsuite/gcc.c-torture/execute/pr68390.c
===================================================================
--- gcc/testsuite/gcc.c-torture/execute/pr68390.c       (nonexistent)
+++ gcc/testsuite/gcc.c-torture/execute/pr68390.c       (working copy)
@@ -0,0 +1,27 @@
+/* { dg-do run }  */
+/* { dg-options "-O2" } */
+
+__attribute__ ((noinline))
+double direct(int x, ...)
+{
+  return x*x;
+}
+
+__attribute__ ((noinline))
+double broken(double (*indirect)(int x, ...), int v)
+{
+  return indirect(v);
+}
+
+int main ()
+{
+  double d1, d2;
+  int i = 2;
+  d1 = broken (direct, i);
+  if (d1 != i*i)
+    {
+      __builtin_abort ();
+    }
+  return 0;
+}
+