Re: [PATCH] Read global value/mask in IPA.

[Aldy Hernandez <aldyh@redhat.com>]

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On 7/17/23 15:14, Aldy Hernandez wrote:
> Instead of reading the known zero bits in IPA, read the value/mask
> pair which is available.
> 
> There is a slight change of behavior here.  I have removed the check
> for SSA_NAME, as the ranger can calculate the range and value/mask for
> INTEGER_CST.  This simplifies the code a bit, since there's no special
> casing when setting the jfunc bits.  The default range for VR is
> undefined, so I think it's safe just to check for undefined_p().

Final round of tests revealed a regression for which I've adjusted the 
testcase.

It turns out g++.dg/ipa/pure-const-3.C fails because IPA can now pick up 
value/mask from any pass that has an integrated ranger.  The test was 
previously disabling evrp and CCP, but now VRP[12], jump threading, and 
DOM can make value/mask adjustments visible to IPA so they must be 
disabled as well.

We've run into these scenarios multiple times in the past-- any 
improvements to the ranger pipeline causes everyone to get smarter, 
making changes visible earlier in the pipeline.

Aldy

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From e1dfd4d6b3d3bf09d55b6ea3ac732462c7030802 Mon Sep 17 00:00:00 2001
From: Aldy Hernandez <aldyh@redhat.com>
Date: Fri, 14 Jul 2023 12:38:16 +0200
Subject: [PATCH] Read global value/mask in IPA.

Instead of reading the known zero bits in IPA, read the value/mask
pair which is available.

There is a slight change of behavior here.  I have removed the check
for SSA_NAME, as the ranger can calculate the range and value/mask for
INTEGER_CST.  This simplifies the code a bit, since there's no special
casing when setting the jfunc bits.  The default range for VR is
undefined, so I think it's safe just to check for undefined_p().

gcc/ChangeLog:

	* ipa-prop.cc (ipa_compute_jump_functions_for_edge): Read global
	value/mask.

gcc/testsuite/ChangeLog:

	* g++.dg/ipa/pure-const-3.C: Adjust for smarter value/mask being
	read by ranger earlier than expected by test.
---
 gcc/ipa-prop.cc                         | 18 ++++++++----------
 gcc/testsuite/g++.dg/ipa/pure-const-3.C |  2 +-
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/gcc/ipa-prop.cc b/gcc/ipa-prop.cc
index 5d790ff1265..4f6ed7b89bd 100644
--- a/gcc/ipa-prop.cc
+++ b/gcc/ipa-prop.cc
@@ -2402,8 +2402,7 @@ ipa_compute_jump_functions_for_edge (struct ipa_func_body_info *fbi,
 	}
       else
 	{
-	  if (TREE_CODE (arg) == SSA_NAME
-	      && param_type
+	  if (param_type
 	      && Value_Range::supports_type_p (TREE_TYPE (arg))
 	      && Value_Range::supports_type_p (param_type)
 	      && irange::supports_p (TREE_TYPE (arg))
@@ -2422,15 +2421,14 @@ ipa_compute_jump_functions_for_edge (struct ipa_func_body_info *fbi,
 	    gcc_assert (!jfunc->m_vr);
 	}
 
-      if (INTEGRAL_TYPE_P (TREE_TYPE (arg))
-	  && (TREE_CODE (arg) == SSA_NAME || TREE_CODE (arg) == INTEGER_CST))
+      if (INTEGRAL_TYPE_P (TREE_TYPE (arg)) && !vr.undefined_p ())
 	{
-	  if (TREE_CODE (arg) == SSA_NAME)
-	    ipa_set_jfunc_bits (jfunc, 0,
-				widest_int::from (get_nonzero_bits (arg),
-						  TYPE_SIGN (TREE_TYPE (arg))));
-	  else
-	    ipa_set_jfunc_bits (jfunc, wi::to_widest (arg), 0);
+	  irange &r = as_a <irange> (vr);
+	  irange_bitmask bm = r.get_bitmask ();
+	  signop sign = TYPE_SIGN (TREE_TYPE (arg));
+	  ipa_set_jfunc_bits (jfunc,
+			      widest_int::from (bm.value (), sign),
+			      widest_int::from (bm.mask (), sign));
 	}
       else if (POINTER_TYPE_P (TREE_TYPE (arg)))
 	{
diff --git a/gcc/testsuite/g++.dg/ipa/pure-const-3.C b/gcc/testsuite/g++.dg/ipa/pure-const-3.C
index b4a4673e86e..e43cf09af27 100644
--- a/gcc/testsuite/g++.dg/ipa/pure-const-3.C
+++ b/gcc/testsuite/g++.dg/ipa/pure-const-3.C
@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-O2 -fno-ipa-vrp -fdump-tree-optimized -fno-tree-ccp -fdisable-tree-evrp"  } */
+/* { dg-options "-O2 -fno-ipa-vrp -fdump-tree-optimized -fno-tree-ccp -fdisable-tree-evrp -fdisable-tree-vrp1 -fdisable-tree-vrp2 -fno-thread-jumps -fno-tree-dominator-opts"  } */
 int *ptr;
 static int barvar;
 static int b(int a);
-- 
2.40.1