[4/7] Use correct promoted mode sign for result of GIMPLE_CALL

[Kugan]

For the following testcase (compiling with -O1; -O2 works fine), we have
a stmt with stm_code SSA_NAME (_7 = _ 6) and for which _6 is defined by
a GIMPLE_CALL. In this case, we are using wrong SUNREG promoted mode
resulting in wrong code. Simple SSA_NAME copes are generally optimized
but when they are not, we can end up using the wrong promoted mode.
Attached patch fixes when we have one copy. I think it might be better
to do this in a while loop but I don't think it can happen in practice.
Please let me know what you think.

  _6 = bar5 (-10);
  ...
  _7 = _6;
  _3 = (long unsigned int) _6;
  ...
  if (_3 != l5.0_4)


for
extern void abort (void);

__attribute__ ((noinline))
static unsigned short int foo5 (int x)
{
  return x;
}

__attribute__ ((noinline))
short int bar5 (int x)
{
  return foo5 (x + 6);
}

unsigned long l5 = (short int) -4;

int
main (void)
{
  if (bar5 (-10) != l5)
    abort ();
  return 0;
}

gcc/ChangeLog:

2015-09-07  Kugan Vivekanandarajah  <kug...@linaro.org>

        * expr.c (expand_expr_real_1): Set proper SUNREG_PROMOTED_MODE for
        SSA_NAME that was set by GIMPLE_CALL and assigned to another
        SSA_NAME of same type.

>From 64ac68bfda1d3e8487827512e6d163b384e8a1cf Mon Sep 17 00:00:00 2001
From: Kugan Vivekanandarajah <kugan.vivekanandara...@linaro.org>
Date: Wed, 2 Sep 2015 12:18:41 +1000
Subject: [PATCH 4/8] use correct promoted sign for result of GIMPLE_CALL

---
 gcc/expr.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/gcc/expr.c b/gcc/expr.c
index bcd87c0..6dac3cf 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9633,7 +9633,22 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
 					   gimple_call_fntype (g),
 					   2);
 	  else
-	    pmode = promote_ssa_mode (ssa_name, &unsignedp);
+	    {
+	      tree rhs;
+	      gimple stmt;
+	      if (code == SSA_NAME
+		  && is_gimple_assign (g)
+		  && (rhs = gimple_assign_rhs1 (g))
+		  && TREE_CODE (rhs) == SSA_NAME
+		  && (stmt = SSA_NAME_DEF_STMT (rhs))
+		  && gimple_code (stmt) == GIMPLE_CALL
+		  && !gimple_call_internal_p (stmt))
+		pmode = promote_function_mode (type, mode, &unsignedp,
+					       gimple_call_fntype (stmt),
+					       2);
+	      else
+		pmode = promote_ssa_mode (ssa_name, &unsignedp);
+	    }
 	  gcc_assert (GET_MODE (decl_rtl) == pmode);
 
 	  temp = gen_lowpart_SUBREG (mode, decl_rtl);
-- 
1.9.1