RISC-V: Use encoded nelts when calling repeating_sequence_p

repeating_sequence_p operates directly on the encoded pattern and does
not derive elements using the .elt() accessor. Passing in the length of
the unencoded vector can cause an out-of-bounds read of the encoded
pattern.

gcc/ChangeLog:

	* config/riscv/riscv-v.cc (rvv_builder::can_duplicate_repeating_sequence_p):
	Use encoded_nelts when calling repeating_sequence_p.
	(rvv_builder::is_repeating_sequence): Ditto.
	(rvv_builder::repeating_sequence_use_merge_profitable_p): Ditto.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>

1 files changed, 3 insertions, 7 deletions

diff --git a/gcc/config/riscv/riscv-v.cc b/gcc/config/riscv/riscv-v.cc
index 0db5c75..c896036 100644
--- a/gcc/config/riscv/riscv-v.cc
+++ b/gcc/config/riscv/riscv-v.cc
@@ -502,9 +502,7 @@ rvv_builder::can_duplicate_repeating_sequence_p ()
       || GET_MODE_SIZE (m_new_inner_mode) > UNITS_PER_WORD
       || !get_vector_mode (m_new_inner_mode, new_size).exists (&m_new_mode))
     return false;
-  if (full_nelts ().is_constant ())
-    return repeating_sequence_p (0, full_nelts ().to_constant (), npatterns ());
-  return nelts_per_pattern () == 1;
+  return repeating_sequence_p (0, encoded_nelts (), npatterns ());
 }
 
 /* Return true if the vector is a simple sequence with one pattern and all
@@ -514,9 +512,7 @@ rvv_builder::is_repeating_sequence ()
 {
   if (npatterns () > 1)
     return false;
-  if (full_nelts ().is_constant ())
-    return repeating_sequence_p (0, full_nelts ().to_constant (), 1);
-  return nelts_per_pattern () == 1;
+  return repeating_sequence_p (0, encoded_nelts (), 1);
 }
 
 /* Return true if it is a repeating sequence that using
@@ -564,7 +560,7 @@ rvv_builder::repeating_sequence_use_merge_profitable_p ()
 
   unsigned int nelts = full_nelts ().to_constant ();
 
-  if (!repeating_sequence_p (0, nelts, npatterns ()))
+  if (!repeating_sequence_p (0, encoded_nelts (), npatterns ()))
     return false;
 
   unsigned int merge_cost = 1;