[RFC][IPA-VRP] Disable setting param of __builtin_constant_p to null

[kugan <kugan.vivekanandarajah@linaro.org>]

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Hi,



VRP assumes that it is run after inlining. Therefore, if there is a call 
to __builtin_constant_p with function parameter, it resolve it to false 
to avoid bogus warnings. Since we use this as an early vrp before 
inling, it leads to  wrong code. As a workaround I have disabled it for 
the time being. That is, this patch is not intended for committing but 
just to get the VRP tested.



Original patch which introduced this also talks about doing it earlier.





Thanks,

Kugan

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From 99f8e7884d582cfae2d7cb50ad59dab7ac6772fc Mon Sep 17 00:00:00 2001
From: Kugan Vivekanandarajah <kugan.vivekanandarajah@linaro.org>
Date: Sat, 25 Jun 2016 11:52:57 +1000
Subject: [PATCH 1/6] Hack-Prevent setting __builtin_constant_p of param to
 null before inlining in Early VRP

---
 gcc/tree-vrp.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index ecfab1f..23c12b5 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -3759,8 +3759,10 @@ extract_range_basic (value_range *vr, gimple *stmt)
 	      && SSA_NAME_IS_DEFAULT_DEF (arg)
 	      && TREE_CODE (SSA_NAME_VAR (arg)) == PARM_DECL)
 	    {
+#if 0
 	      set_value_range_to_null (vr, type);
 	      return;
+#endif
 	    }
 	  break;
 	  /* Both __builtin_ffs* and __builtin_popcount return
-- 
1.9.1