Check for matching CONST_VECTOR encodings [PR99929]

PR99929 is one of those “how did we get away with this for so long”
bugs: the equality routines weren't checking whether two variable-length
CONST_VECTORs had the same encoding.  This meant that:

   { 1, 0, 0, 0, 0, 0, ... }

would appear to be equal to:

   { 1, 0, 1, 0, 1, 0, ... }

since both are represented using the elements { 1, 0 }.

gcc/
	PR rtl-optimization/99929
	* rtl.h (same_vector_encodings_p): New function.
	* cse.c (exp_equiv_p): Check that CONST_VECTORs have the same encoding.
	* cselib.c (rtx_equal_for_cselib_1): Likewise.
	* jump.c (rtx_renumbered_equal_p): Likewise.
	* lra-constraints.c (operands_match_p): Likewise.
	* reload.c (operands_match_p): Likewise.
	* rtl.c (rtx_equal_p_cb, rtx_equal_p): Likewise.

gcc/testsuite/
	* gcc.target/aarch64/sve/pr99929_1.c: New file.
	* gcc.target/aarch64/sve/pr99929_2.c: Likewise.

1 files changed, 5 insertions, 0 deletions

diff --git a/gcc/cse.c b/gcc/cse.c
index 37c6959..df191d5 100644
--- a/gcc/cse.c
+++ b/gcc/cse.c
@@ -2637,6 +2637,11 @@ exp_equiv_p (const_rtx x, const_rtx y, int validate, bool for_gcse)
     CASE_CONST_UNIQUE:
       return x == y;
 
+    case CONST_VECTOR:
+      if (!same_vector_encodings_p (x, y))
+	return false;
+      break;
+
     case LABEL_REF:
       return label_ref_label (x) == label_ref_label (y);