From: Deng Jianbo <dengjianbo@loongson.cn>
Date: Tue, 31 Dec 2024 11:33:23 +0000 (+0800)
Subject: LoongArch: Optimize initializing fp resgister to zero
X-Git-Tag: basepoints/gcc-16~2936
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=61400b669688848dc764d946a4d16fb51a27e286;p=thirdparty%2Fgcc.git

LoongArch: Optimize initializing fp resgister to zero

In LoongArch, currently uses instruction movgr2fr.{d|w} to move zero
from fixed-point register to floating-pointer regsiter for initializing
fp register to zero. When LSX or LASX is enabled, we can use instruction
vxor.v which has lower latency than instruction movgr2fr.{d|w} to set fp
register to zero directly.

gcc/ChangeLog:

	* config/loongarch/loongarch.cc (loongarch_output_move):
	Optimize instructions for initializing fp regsiter to zero.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/mov-zero-1.c: New test.
	* gcc.target/loongarch/mov-zero-2.c: New test.
---

diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index 89237c377e77..d506354c48a0 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -4772,6 +4772,8 @@ loongarch_output_move (rtx dest, rtx src)
 		      gcc_unreachable ();
 		    }
 		}
+	      if (ISA_HAS_LSX && src == CONST0_RTX (GET_MODE (src)))
+		return "vxor.v\t%w0,%w0,%w0";
 
 	      return dbl_p ? "movgr2fr.d\t%0,%z1" : "movgr2fr.w\t%0,%z1";
 	    }
diff --git a/gcc/testsuite/gcc.target/loongarch/mov-zero-1.c b/gcc/testsuite/gcc.target/loongarch/mov-zero-1.c
new file mode 100644
index 000000000000..4744f2f2fdb9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/mov-zero-1.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mlsx" } */
+/* { dg-final { scan-assembler-times "vxor\\.v" 2 } } */
+
+double
+get_double_zero ()
+{
+  return 0;
+}
+
+float
+get_float_zero ()
+{
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/loongarch/mov-zero-2.c b/gcc/testsuite/gcc.target/loongarch/mov-zero-2.c
new file mode 100644
index 000000000000..6cb48052d0b4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/mov-zero-2.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mno-lsx" } */
+/* { dg-final { scan-assembler-times "movgr2fr" 2 } } */
+
+double
+get_double_zero ()
+{
+  return 0;
+}
+
+float
+get_float_zero ()
+{
+  return 0;
+}