[gcc r15-6751] [PR118017][LRA]: Don't inherit reg of non-uniform reg class

[Vladimir Makarov via Gcc-cvs]

https://gcc.gnu.org/g:fab96de044f1f023f52d43af866205d17d8895fb

commit r15-6751-gfab96de044f1f023f52d43af866205d17d8895fb
Author: Vladimir N. Makarov <vmaka...@redhat.com>
Date:   Thu Jan 9 16:22:02 2025 -0500

    [PR118017][LRA]: Don't inherit reg of non-uniform reg class
    
    In the PR case LRA inherited value of register of class INT_SSE_REGS
    which resulted in LRA cycling when LRA tried to use different move
    alternatives with SSE/general regs and memory.  The patch rejects to
    inherit such (non-uniform) classes to prevent cycling.
    
    gcc/ChangeLog:
    
            PR target/118017
            * lra-constraints.cc (inherit_reload_reg): Check reg class on 
uniformity.
    
    gcc/testsuite/ChangeLog:
    
            PR target/118017
            * gcc.target/i386/pr118017.c: New.

Diff:
---
 gcc/lra-constraints.cc                   | 14 ++++++++++++++
 gcc/testsuite/gcc.target/i386/pr118017.c | 21 +++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index a0f05b290dde..8f32e98f1c47 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -5878,6 +5878,20 @@ inherit_reload_reg (bool def_p, int original_regno,
        }
       return false;
     }
+  if (ira_reg_class_min_nregs[rclass][GET_MODE (original_reg)]
+      != ira_reg_class_max_nregs[rclass][GET_MODE (original_reg)])
+    {
+      if (lra_dump_file != NULL)
+       {
+         fprintf (lra_dump_file,
+                  "    Rejecting inheritance for %d "
+                  "because of requiring non-uniform class %s\n",
+                  original_regno, reg_class_names[rclass]);
+         fprintf (lra_dump_file,
+                  "    >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>\n");
+       }
+      return false;
+    }
   new_reg = lra_create_new_reg (GET_MODE (original_reg), original_reg,
                                rclass, NULL, "inheritance");
   start_sequence ();
diff --git a/gcc/testsuite/gcc.target/i386/pr118017.c 
b/gcc/testsuite/gcc.target/i386/pr118017.c
new file mode 100644
index 000000000000..c82d71e8d293
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr118017.c
@@ -0,0 +1,21 @@
+/* PR target/118017 */
+/* { dg-do compile } */
+/* { dg-options "-Og -frounding-math -mno-80387 -mno-mmx -Wno-psabi" } */
+
+typedef __attribute__((__vector_size__ (64))) _Float128 F;
+typedef __attribute__((__vector_size__ (64))) _Decimal64 G;
+typedef __attribute__((__vector_size__ (64))) _Decimal128 H;
+
+void
+bar(_Float32, _BitInt(1025), _BitInt(1025), _Float128, __int128, __int128,  F,
+        int, int, G, _Float64, __int128, __int128, H, F);
+
+
+void
+foo ()
+{
+  bar ((__int128)68435455, 0, 0, 0, 0, 0, (F){}, 0, 0, 
(G){3689348814741910323},
+       0, 0, 0, (H){0, (_Decimal128) ((__int128) 860933398830926 << 64),
+       (_Decimal128) ((__int128) 966483857959145 << 64), 4},
+       (F){(__int128) 3689348814741910323 << 64 | 3});
+}