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

Message ID 20221211154519.2681701-1-ibuclaw@gdcproject.org
State New
Headers show
Series [committed] d: Expand bsr intrinsic as `clz(arg) ^ (argsize - 1)' | expand

Commit Message

Iain Buclaw Dec. 11, 2022, 3:45 p.m. UTC 
Hi,

This patch tweaks the code expansion of the D intrinsic bsr() function.

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.

Bootstrapped and regression tested on x86_64-linux-gnu/-m32.

Committed to mainline.

Regards,
Iain.

---
gcc/d/ChangeLog:

	* intrinsics.cc (expand_intrinsic_bsf): Fix comment.
	(expand_intrinsic_bsr): Use BIT_XOR_EXPR instead of MINUS_EXPR.
---
 gcc/d/intrinsics.cc | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)
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Patch

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