[gcc r15-9002] ipa-sra: Don't change return type to void if there are musttail calls [PR119484]

[Jakub Jelinek via Gcc-cvs]

https://gcc.gnu.org/g:c95f5a0c0719ad5b23f605b4d8f8dd3689a0066b

commit r15-9002-gc95f5a0c0719ad5b23f605b4d8f8dd3689a0066b
Author: Jakub Jelinek <ja...@redhat.com>
Date:   Fri Mar 28 10:48:31 2025 +0100

    ipa-sra: Don't change return type to void if there are musttail calls 
[PR119484]
    
    The following testcase is rejected, because IPA-SRA decides to
    turn bar.constprop call into bar.constprop.isra which returns void.
    While there is no explicit lhs on the call, as it is a musttail call
    the tailc pass checks if IPA-VRP returns singleton from that function
    and the function returns the same value and in that case it still turns
    it into a tail call.  This can't work with IPA-SRA changing it into
    void returning function though.
    
    The following patch fixes this by forcing returning the original type
    if there are musttail calls.
    
    2025-03-28  Jakub Jelinek  <ja...@redhat.com>
    
            PR ipa/119484
            * ipa-sra.cc (isra_analyze_call): Don't set m_return_ignored if
            gimple_call_must_tail_p even if it doesn't have lhs.
    
            * c-c++-common/pr119484.c: New test.

Diff:
---
 gcc/ipa-sra.cc                        |  6 +++++-
 gcc/testsuite/c-c++-common/pr119484.c | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/gcc/ipa-sra.cc b/gcc/ipa-sra.cc
index 5d1703ed394f..1331ba49b507 100644
--- a/gcc/ipa-sra.cc
+++ b/gcc/ipa-sra.cc
@@ -2242,7 +2242,11 @@ isra_analyze_call (cgraph_edge *cs)
          BITMAP_FREE (analyzed);
        }
     }
-  else
+  /* Don't set m_return_ignored for musttail calls.  The tailc/musttail passes
+     compare the returned value against the IPA-VRP return value range if
+     it is a singleton, but if the call is changed to something which doesn't
+     return anything, it will always fail.  */
+  else if (!gimple_call_must_tail_p (call_stmt))
     csum->m_return_ignored = true;
 }
 
diff --git a/gcc/testsuite/c-c++-common/pr119484.c 
b/gcc/testsuite/c-c++-common/pr119484.c
new file mode 100644
index 000000000000..6ae7c9a7491f
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr119484.c
@@ -0,0 +1,21 @@
+/* PR ipa/119484 */
+/* { dg-do compile { target musttail } } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "bar\[.a-z0-9]* \\\(\[^\n\r]*\\\); 
\\\[tail call\\\] \\\[must tail call\\\]" 1 "optimized" } } */
+
+void foo (int);
+
+[[gnu::noinline]] static int
+bar (int x)
+{
+  foo (x);
+  return 0;
+}
+
+int
+baz (int x)
+{
+  if (x == 1)
+    [[gnu::musttail]] return bar (x);
+  return 0;
+}