[gcc(refs/vendors/riscv/heads/gcc-14-with-riscv-opts)] [committed][PR rtl-optimization/116544] Fix test for promoted subregs

[Jeff Law via Gcc-cvs]

https://gcc.gnu.org/g:f35d49f0eb8ffc614cf233ad05b2fe86791c6719

commit f35d49f0eb8ffc614cf233ad05b2fe86791c6719
Author: Jeff Law <j...@ventanamicro.com>
Date:   Sun Sep 1 22:16:04 2024 -0600

    [committed][PR rtl-optimization/116544] Fix test for promoted subregs
    
    This is a small bug in the ext-dce code's handling of promoted subregs.
    
    Essentially when we see a promoted subreg we need to make additional bit 
groups
    live as various parts of the RTL path know that an extension of a suitably
    promoted subreg can be trivially eliminated.
    
    When I added support for dealing with this quirk I failed to account for the
    larger modes properly and it ignored the case when the size of the inner 
object
    was > 32 bits.  Opps.
    
    This does _not_ fix the outstanding x86 issue.  That's caused by something
    completely different and more concerning ;(
    
    Bootstrapped and regression tested on x86.  Obviously fixes the testcase on
    riscv as well.
    
    Pushing to the trunk.
    
            PR rtl-optimization/116544
    gcc/
            * ext-dce.cc (ext_dce_process_uses): Fix thinko in promoted subreg
            handling.
    
    gcc/testsuite/
            * gcc.dg/torture/pr116544.c: New test.
    
    (cherry picked from commit 0562976d62e095f3a00c799288dee4e5b20114e2)

Diff:
---
 gcc/ext-dce.cc                          |  2 +-
 gcc/testsuite/gcc.dg/torture/pr116544.c | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/gcc/ext-dce.cc b/gcc/ext-dce.cc
index fbe9719a8d5..dcd55cf1183 100644
--- a/gcc/ext-dce.cc
+++ b/gcc/ext-dce.cc
@@ -846,7 +846,7 @@ ext_dce_process_uses (rtx_insn *insn, rtx obj,
            bitmap_set_bit (livenow, rn + 1);
          if (size > 16)
            bitmap_set_bit (livenow, rn + 2);
-         if (size == 32)
+         if (size >= 32)
            bitmap_set_bit (livenow, rn + 3);
          iter.skip_subrtxes ();
        }
diff --git a/gcc/testsuite/gcc.dg/torture/pr116544.c 
b/gcc/testsuite/gcc.dg/torture/pr116544.c
new file mode 100644
index 00000000000..15f52fecb3b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr116544.c
@@ -0,0 +1,22 @@
+/* { dg-options "-fno-strict-aliasing -fwrapv" }
+/* { dg-do run { target longlong64 } } */
+
+extern void abort (void);
+long long a;
+signed char b[60];
+signed char c;
+long long d[60];
+int e[30];
+long long *f = d;
+static void g(long long *j, long k) { *j = k; }
+int main() {
+  d[5] = 0x100000000;
+  for (int h = 2; h < 7; h += 3)
+    for (int i = 0; i < (c || b[h]) + 10; i += 11)
+      e[2] = f[h];
+  g(&a, e[2]);
+  if (a != 0)
+    abort ();
+  return 0;
+}
+