[gcc r13-4601] d: Expand bsr intrinsic as `clz(arg) ^ (argsize - 1)'

[gcc r13-4601] d: Expand bsr intrinsic as `clz(arg) ^ (argsize - 1)'

[Iain Buclaw]

https://gcc.gnu.org/g:cc7f509d3c0b3ab63891cf7ca2def0fdfb3642c4

commit r13-4601-gcc7f509d3c0b3ab63891cf7ca2def0fdfb3642c4
Author: Iain Buclaw <ibuclaw@gdcproject.org>
Date:   Sat Dec 10 17:17:35 2022 +0100

    d: Expand bsr intrinsic as `clz(arg) ^ (argsize - 1)'
    
    As well as removing unnecessary casts, this results in less temporaries
    being generated during the initial gimple lowering pass.  Otherwise the
    code generated is identical to the former intrinsic expansion.
    
    gcc/d/ChangeLog:
    
            * intrinsics.cc (expand_intrinsic_bsf): Fix comment.
            (expand_intrinsic_bsr): Use BIT_XOR_EXPR instead of MINUS_EXPR.

Diff:
---
 gcc/d/intrinsics.cc | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/gcc/d/intrinsics.cc b/gcc/d/intrinsics.cc
index 6d9f74a6d7a..46380e512c4 100644
--- a/gcc/d/intrinsics.cc
+++ b/gcc/d/intrinsics.cc
@@ -525,7 +525,7 @@ call_builtin_fn (tree callexp, built_in_function code, int n, ...)
 static tree
 expand_intrinsic_bsf (tree callexp)
 {
-  /* The bsr() intrinsic gets turned into __builtin_ctz(arg).
+  /* The bsf() intrinsic gets turned into __builtin_ctz(arg).
      The return value is supposed to be undefined if arg is zero.  */
   tree arg = CALL_EXPR_ARG (callexp, 0);
   int argsize = TYPE_PRECISION (TREE_TYPE (arg));
@@ -554,11 +554,11 @@ expand_intrinsic_bsf (tree callexp)
 static tree
 expand_intrinsic_bsr (tree callexp)
 {
-  /* The bsr() intrinsic gets turned into (size - 1) - __builtin_clz(arg).
+  /* The bsr() intrinsic gets turned into __builtin_clz(arg) ^ (size - 1).
      The return value is supposed to be undefined if arg is zero.  */
   tree arg = CALL_EXPR_ARG (callexp, 0);
-  tree type = TREE_TYPE (arg);
-  int argsize = TYPE_PRECISION (type);
+  tree type = TREE_TYPE (callexp);
+  int argsize = TYPE_PRECISION (TREE_TYPE (arg));
 
   /* Which variant of __builtin_clz* should we call?  */
   built_in_function code = (argsize <= INT_TYPE_SIZE) ? BUILT_IN_CLZ
@@ -570,13 +570,8 @@ expand_intrinsic_bsr (tree callexp)
 
   tree result = call_builtin_fn (callexp, code, 1, arg);
 
-  /* Handle int -> long conversions.  */
-  if (TREE_TYPE (result) != type)
-    result = fold_convert (type, result);
-
-  result = fold_build2 (MINUS_EXPR, type,
-			build_integer_cst (argsize - 1, type), result);
-  return fold_convert (TREE_TYPE (callexp), result);
+  return fold_build2 (BIT_XOR_EXPR, type, result,
+		      build_integer_cst (argsize - 1, type));
 }
 
 /* Expand a front-end intrinsic call to INTRINSIC, which is either a call to