[gcc r13-4706] ipa-sra: Consider the first parameter of methods safe to dereference

[Martin Jambor <jamborm@gcc.gnu.org>]

https://gcc.gnu.org/g:0e9495303db062cf118869b7526132b5821833e9

commit r13-4706-g0e9495303db062cf118869b7526132b5821833e9
Author: Martin Jambor <mjambor@suse.cz>
Date:   Wed Dec 14 19:01:11 2022 +0100

    ipa-sra: Consider the first parameter of methods safe to dereference
    
    Honza requested this after reviewing the patch that taught IPA-SRA
    that REFERENCE_TYPEs are always non-NULL that the pass also handles
    the first parameters of methods, this pointers, in the same way.  So
    this patch does that.
    
    gcc/ChangeLog:
    
    2022-12-14  Martin Jambor  <mjambor@suse.cz>
    
            * ipa-sra.cc (create_parameter_descriptors): Consider the first
            parameter of a method safe to dereference.
    
    gcc/testsuite/ChangeLog:
    
    2022-12-14  Martin Jambor  <mjambor@suse.cz>
    
            * g++.dg/ipa/ipa-sra-6.C: New test.

Diff:
---
 gcc/ipa-sra.cc                       |  7 +++-
 gcc/testsuite/g++.dg/ipa/ipa-sra-6.C | 62 ++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/gcc/ipa-sra.cc b/gcc/ipa-sra.cc
index bcabdedfc6c..6fe336eeb19 100644
--- a/gcc/ipa-sra.cc
+++ b/gcc/ipa-sra.cc
@@ -1206,7 +1206,12 @@ create_parameter_descriptors (cgraph_node *node,
       if (POINTER_TYPE_P (type))
 	{
 	  desc->by_ref = true;
-	  desc->safe_ref = (TREE_CODE (type) == REFERENCE_TYPE);
+	  if (TREE_CODE (type) == REFERENCE_TYPE
+	      || (num == 0
+		  && TREE_CODE (TREE_TYPE (node->decl)) == METHOD_TYPE))
+	    desc->safe_ref = true;
+	  else
+	    desc->safe_ref = false;
 	  type = TREE_TYPE (type);
 
 	  if (TREE_CODE (type) == FUNCTION_TYPE
diff --git a/gcc/testsuite/g++.dg/ipa/ipa-sra-6.C b/gcc/testsuite/g++.dg/ipa/ipa-sra-6.C
new file mode 100644
index 00000000000..d6b7822533f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ipa/ipa-sra-6.C
@@ -0,0 +1,62 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-ipa-sra"  } */
+
+namespace {
+
+class C
+{
+
+  int mi;
+
+public:
+  C (int i)
+    : mi(i)
+  {}
+
+  void foo (int c);
+};
+
+volatile int vi;
+
+
+void __attribute__((noinline))
+C::foo (int cond)
+{
+  int i;
+  if (cond)
+    i = mi;
+  else
+    i = 0;
+  vi = i;
+}
+
+static C c_instance(1);
+}
+
+void __attribute__((noinline))
+bar (C *p, int cond)
+{
+  p->foo (cond);
+}
+
+
+class C *gp;
+
+void something(void);
+
+void
+baz (int cond)
+{
+  C c(vi);
+  gp = &c;
+  something ();
+  bar (gp, cond);
+}
+
+void
+hoo(void)
+{
+  gp = &c_instance;
+}
+
+/* { dg-final { scan-ipa-dump "Will split parameter" "sra" } } */