[gcc r16-2285] RISC-V: Fix vsetvl merge rule.

[Robin Dapp via Gcc-cvs]

https://gcc.gnu.org/g:9041f2bff8202d9b87d8c27f21e4ffa8d50b36a3

commit r16-2285-g9041f2bff8202d9b87d8c27f21e4ffa8d50b36a3
Author: Robin Dapp <rd...@ventanamicro.com>
Date:   Mon Jul 14 13:53:12 2025 +0200

    RISC-V: Fix vsetvl merge rule.
    
    In PR120297 we fuse
      vsetvl e8,mf2,...
      vsetvl e64,m1,...
    into
      vsetvl e64,m4,...
    
    Individually, that's ok but we also change the new vsetvl's demand to
    "SEW only" even though the first original one demanded SEW >= 8 and
    ratio = 16.
    
    As we forget the ratio after the merge we find that the vsetvl following
    the merged one has ratio = 64 demand and we fuse into
      vsetvl e64,m1,..
    which obviously doesn't have ratio = 16 any more.
    
    Regtested on rv64gcv_zvl512b.
    
            PR target/120297
    
    gcc/ChangeLog:
    
            * config/riscv/riscv-vsetvl.def: Do not forget ratio demand of
            previous vsetvl.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/riscv/rvv/pr120297.c: New test.

Diff:
---
 gcc/config/riscv/riscv-vsetvl.def             |  6 ++--
 gcc/testsuite/gcc.target/riscv/rvv/pr120297.c | 50 +++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/gcc/config/riscv/riscv-vsetvl.def 
b/gcc/config/riscv/riscv-vsetvl.def
index d7a5ada772d0..0f999d2276d4 100644
--- a/gcc/config/riscv/riscv-vsetvl.def
+++ b/gcc/config/riscv/riscv-vsetvl.def
@@ -79,7 +79,7 @@ DEF_SEW_LMUL_RULE (sew_only, sew_only, sew_only, sew_eq_p, 
sew_eq_p, nop)
 DEF_SEW_LMUL_RULE (sew_only, ge_sew, sew_only,
                   sew_ge_and_prev_sew_le_next_max_sew_p, sew_ge_p, nop)
 DEF_SEW_LMUL_RULE (
-  sew_only, ratio_and_ge_sew, sew_lmul,
+  sew_only, ratio_and_ge_sew, ratio_and_ge_sew,
   sew_ge_and_prev_sew_le_next_max_sew_and_next_ratio_valid_for_prev_sew_p,
   always_false, modify_lmul_with_next_ratio)
 
@@ -104,9 +104,9 @@ DEF_SEW_LMUL_RULE (ratio_and_ge_sew, sew_lmul, sew_lmul,
 DEF_SEW_LMUL_RULE (ratio_and_ge_sew, ratio_only, ratio_and_ge_sew, ratio_eq_p,
                   ratio_eq_p, use_max_sew_and_lmul_with_prev_ratio)
 DEF_SEW_LMUL_RULE (
-  ratio_and_ge_sew, sew_only, sew_only,
+  ratio_and_ge_sew, sew_only, ratio_and_ge_sew,
   sew_le_and_next_sew_le_prev_max_sew_and_prev_ratio_valid_for_next_sew_p,
-  always_false, use_next_sew_with_prev_ratio)
+  sew_eq_p, use_next_sew_with_prev_ratio)
 DEF_SEW_LMUL_RULE (ratio_and_ge_sew, ge_sew, ratio_and_ge_sew,
                   max_sew_overlap_and_prev_ratio_valid_for_next_sew_p,
                   sew_ge_p, use_max_sew_and_lmul_with_prev_ratio)
diff --git a/gcc/testsuite/gcc.target/riscv/rvv/pr120297.c 
b/gcc/testsuite/gcc.target/riscv/rvv/pr120297.c
new file mode 100644
index 000000000000..3d1845d0fe66
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/pr120297.c
@@ -0,0 +1,50 @@
+/* { dg-do run } */
+/* { dg-require-effective-target riscv_v_ok } */
+/* { dg-options "-march=rv64gcv -mabi=lp64d -O3 -fwhole-program" } */
+
+unsigned a;
+short c;
+char d;
+unsigned long e;
+_Bool f[10][10];
+unsigned g[10];
+long long ak;
+char i = 7;
+long long t[10];
+short x[10][10][10][10];
+short y[10][10][10][10];
+
+void
+h (char i, long long t[], short x[][10][10][10], short y[][10][10][10],
+   _Bool aa)
+{
+  for (int j = 2; j < 8; j += 2)
+    {
+      for (short k = 0; k < 10; k++)
+       {
+         for (int l = 3; l < 8; l += 2)
+           a = x[1][j][k][l];
+         c = x[c][1][1][c];
+       }
+      for (int k = 0; k < 10; k++)
+       {
+         f[2][k] |= (_Bool) t[c];
+         g[c] = t[c + 1];
+         d += y[j][1][k][k];
+         e = e > i ? e : i;
+       }
+    }
+}
+
+int
+main ()
+{
+  t[c] = 1;
+  h (i, t, x, y, a);
+  for (int j = 0; j < 10; ++j)
+    for (int k = 0; k < 10; ++k)
+      ak ^= f[j][k] + 238516665 + (ak >> 2);
+  ak ^= g[c] + 238516665 + (ak >> 2);
+  if (ak != 234635118ull)
+    __builtin_abort ();
+}