[gcc(refs/vendors/redhat/heads/gcc-8-branch)] Check for matching CONST_VECTOR encodings [PR99929]

[gcc(refs/vendors/redhat/heads/gcc-8-branch)] Check for matching CONST_VECTOR encodings [PR99929]

[Jakub Jelinek]

https://gcc.gnu.org/g:cc89aab0e924f5f8f871b35180ff139955893516

commit cc89aab0e924f5f8f871b35180ff139955893516
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Mon Apr 26 09:36:48 2021 +0100

    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.
    
    (cherry picked from commit a87d3f964df31d4fbceb822c6d293e85c117d992)

Diff:
---
 gcc/cse.c             |  5 +++++
 gcc/cselib.c          |  5 +++++
 gcc/jump.c            |  5 +++++
 gcc/lra-constraints.c |  5 +++++
 gcc/reload.c          |  5 +++++
 gcc/rtl.c             | 10 ++++++++++
 gcc/rtl.h             | 17 +++++++++++++++++
 7 files changed, 52 insertions(+)

diff --git a/gcc/cse.c b/gcc/cse.c
index a73a771041a..2382b24d816 100644
--- a/gcc/cse.c
+++ b/gcc/cse.c
@@ -2627,6 +2627,11 @@ 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);
 
diff --git a/gcc/cselib.c b/gcc/cselib.c
index 5a978c1f4b8..de5d9d4e2ba 100644
--- a/gcc/cselib.c
+++ b/gcc/cselib.c
@@ -938,6 +938,11 @@ rtx_equal_for_cselib_1 (rtx x, rtx y, machine_mode memmode, int depth)
     case DEBUG_EXPR:
       return 0;
 
+    case CONST_VECTOR:
+      if (!same_vector_encodings_p (x, y))
+	return false;
+      break;
+
     case DEBUG_IMPLICIT_PTR:
       return DEBUG_IMPLICIT_PTR_DECL (x)
 	     == DEBUG_IMPLICIT_PTR_DECL (y);
diff --git a/gcc/jump.c b/gcc/jump.c
index f379048f636..112317cd7e1 100644
--- a/gcc/jump.c
+++ b/gcc/jump.c
@@ -1767,6 +1767,11 @@ rtx_renumbered_equal_p (const_rtx x, const_rtx y)
     CASE_CONST_UNIQUE:
       return 0;
 
+    case CONST_VECTOR:
+      if (!same_vector_encodings_p (x, y))
+	return false;
+      break;
+
     case LABEL_REF:
       /* We can't assume nonlocal labels have their following insns yet.  */
       if (LABEL_REF_NONLOCAL_P (x) || LABEL_REF_NONLOCAL_P (y))
diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
index 1e98df48132..80502441945 100644
--- a/gcc/lra-constraints.c
+++ b/gcc/lra-constraints.c
@@ -759,6 +759,11 @@ operands_match_p (rtx x, rtx y, int y_hard_regno)
     CASE_CONST_UNIQUE:
       return false;
 
+    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);
     case SYMBOL_REF:
diff --git a/gcc/reload.c b/gcc/reload.c
index 88299a8a905..0e4f72065a2 100644
--- a/gcc/reload.c
+++ b/gcc/reload.c
@@ -2291,6 +2291,11 @@ operands_match_p (rtx x, rtx y)
     CASE_CONST_UNIQUE:
       return 0;
 
+    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);
     case SYMBOL_REF:
diff --git a/gcc/rtl.c b/gcc/rtl.c
index dc03e1e5426..61cd4474586 100644
--- a/gcc/rtl.c
+++ b/gcc/rtl.c
@@ -460,6 +460,11 @@ rtx_equal_p_cb (const_rtx x, const_rtx y, rtx_equal_p_callback_function cb)
     CASE_CONST_UNIQUE:
       return 0;
 
+    case CONST_VECTOR:
+      if (!same_vector_encodings_p (x, y))
+	return false;
+      break;
+
     case DEBUG_IMPLICIT_PTR:
       return DEBUG_IMPLICIT_PTR_DECL (x)
 	     == DEBUG_IMPLICIT_PTR_DECL (y);
@@ -602,6 +607,11 @@ rtx_equal_p (const_rtx x, const_rtx y)
     CASE_CONST_UNIQUE:
       return 0;
 
+    case CONST_VECTOR:
+      if (!same_vector_encodings_p (x, y))
+	return false;
+      break;
+
     case DEBUG_IMPLICIT_PTR:
       return DEBUG_IMPLICIT_PTR_DECL (x)
 	     == DEBUG_IMPLICIT_PTR_DECL (y);
diff --git a/gcc/rtl.h b/gcc/rtl.h
index 31567126c83..fb2e088f7d1 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -3035,6 +3035,23 @@ vec_series_p (const_rtx x, rtx *base_out, rtx *step_out)
   return const_vec_series_p (x, base_out, step_out);
 }
 
+/* Return true if CONST_VECTORs X and Y, which are known to have the same mode,
+   also have the same encoding.  This means that they are equal whenever their
+   operands are equal.  */
+
+inline bool
+same_vector_encodings_p (const_rtx x, const_rtx y)
+{
+  /* Don't be fussy about the encoding of constant-length vectors,
+     since XVECEXP (X, 0) and XVECEXP (Y, 0) list all the elements anyway.  */
+  if (poly_uint64 (CONST_VECTOR_NUNITS (x)).is_constant ())
+    return true;
+
+  return (CONST_VECTOR_NPATTERNS (x) == CONST_VECTOR_NPATTERNS (y)
+	  && (CONST_VECTOR_NELTS_PER_PATTERN (x)
+	      == CONST_VECTOR_NELTS_PER_PATTERN (y)));
+}
+
 /* Return the unpromoted (outer) mode of SUBREG_PROMOTED_VAR_P subreg X.  */
 
 inline scalar_int_mode