[gcc r14-3819] LoongArch: Slightly simplify loongarch_block_move_straight

[Xi Ruoyao <xry111@gcc.gnu.org>]

https://gcc.gnu.org/g:c0bb7a6f39e58717d34c9459586c0b1d5db16d89

commit r14-3819-gc0bb7a6f39e58717d34c9459586c0b1d5db16d89
Author: Xi Ruoyao <xry111@xry111.site>
Date:   Fri Sep 8 00:29:57 2023 +0800

    LoongArch: Slightly simplify loongarch_block_move_straight
    
    gcc/ChangeLog:
    
            * config/loongarch/loongarch.cc (loongarch_block_move_straight):
            Check precondition (delta must be a power of 2) and use
            popcount_hwi instead of a homebrew loop.

Diff:
---
 gcc/config/loongarch/loongarch.cc | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index 509ef2b97f1c..845fad5a8e8b 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -5225,9 +5225,8 @@ loongarch_block_move_straight (rtx dest, rtx src, HOST_WIDE_INT length,
      emit two ld.d/st.d pairs, one ld.w/st.w pair, and one ld.b/st.b
      pair.  For each load/store pair we use a dedicated register to keep
      the pipeline as populated as possible.  */
-  HOST_WIDE_INT num_reg = length / delta;
-  for (delta_cur = delta / 2; delta_cur != 0; delta_cur /= 2)
-    num_reg += !!(length & delta_cur);
+  gcc_assert (pow2p_hwi (delta));
+  HOST_WIDE_INT num_reg = length / delta + popcount_hwi (length % delta);
 
   /* Allocate a buffer for the temporary registers.  */
   regs = XALLOCAVEC (rtx, num_reg);