[PATCH] ipa-sra: Disable candidates with no known callers (PR 110276)

[Martin Jambor <mjambor@suse.cz>]

Hi,

In IPA-SRA we use can_be_local_p () predicate rather than just plain
local call graph flag in order to figure out whether the node is a
part of an external API that we cannot change.  Although there are
cases where this can allow more transformations, it also means we can
analyze functions which have no callers at all, which is pointless.

Moreover, it makes an assert of hint propagation trigger, which checks
that we have looked at callers before processing hints that come from
them.  This has been reported as PR 110276.

This patch simply adds a check that a node has at least one caller
into the early checks and makes the node a non-candidate for any
transformation if it does not.

Bootstrapped and tested on x86_64-linux, LTO bootstrap is still
underway.  OK if it passes too?

Thanks,

Martin


gcc/ChangeLog:

2023-06-16  Martin Jambor  <mjambor@suse.cz>

	PR ipa/110276
	* ipa-sra.cc (struct caller_issues): New field there_is_one.
	(check_for_caller_issues): Set it.
	(check_all_callers_for_issues): Check it.

gcc/testsuite/ChangeLog:

2023-06-16  Martin Jambor  <mjambor@suse.cz>

	PR ipa/110276
	* gcc.dg/ipa/pr110276.c: New test.
---
 gcc/ipa-sra.cc                      | 11 +++++++++++
 gcc/testsuite/gcc.dg/ipa/pr110276.c | 15 +++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/ipa/pr110276.c

diff --git a/gcc/ipa-sra.cc b/gcc/ipa-sra.cc
index 3fee8fb22ce..21d281a9756 100644
--- a/gcc/ipa-sra.cc
+++ b/gcc/ipa-sra.cc
@@ -3074,6 +3074,8 @@ struct caller_issues
   cgraph_node *candidate;
   /* There is a thunk among callers.  */
   bool thunk;
+  /* Set if there is at least one caller that is OK.  */
+  bool there_is_one;
   /* Call site with no available information.  */
   bool unknown_callsite;
   /* Call from outside the candidate's comdat group.  */
@@ -3116,6 +3118,8 @@ check_for_caller_issues (struct cgraph_node *node, void *data)
 
       if (csum->m_bit_aligned_arg)
 	issues->bit_aligned_aggregate_argument = true;
+
+      issues->there_is_one = true;
     }
   return false;
 }
@@ -3170,6 +3174,13 @@ check_all_callers_for_issues (cgraph_node *node)
       for (unsigned i = 0; i < param_count; i++)
 	(*ifs->m_parameters)[i].split_candidate = false;
     }
+  if (!issues.there_is_one)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "There is no call to %s that we can modify.  "
+		 "Disabling all modifications.\n", node->dump_name ());
+      return true;
+    }
   return false;
 }
 
diff --git a/gcc/testsuite/gcc.dg/ipa/pr110276.c b/gcc/testsuite/gcc.dg/ipa/pr110276.c
new file mode 100644
index 00000000000..5a1e2f3fb1c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ipa/pr110276.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+typedef long (*EFI_PCI_IO_PROTOCOL_CONFIG)();
+typedef struct {
+  EFI_PCI_IO_PROTOCOL_CONFIG Read;
+} EFI_PCI_IO_PROTOCOL_CONFIG_ACCESS;
+typedef struct {
+  EFI_PCI_IO_PROTOCOL_CONFIG_ACCESS Pci;
+} EFI_PCI_IO_PROTOCOL;
+int init_regs_0;
+static void __attribute__((constructor)) init(EFI_PCI_IO_PROTOCOL *pci_io) {
+  if (init_regs_0)
+    pci_io->Pci.Read();
+}
-- 
2.40.1