[gcc/devel/ranger] aarch64: Avoid creating an unused register

[Aldy Hernandez]

https://gcc.gnu.org/g:0df28e68fd126d9c3356a3d314be383a877b74a7

commit 0df28e68fd126d9c3356a3d314be383a877b74a7
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Thu Feb 20 15:04:19 2020 +0000

    aarch64: Avoid creating an unused register
    
    The rsqrt path of aarch64_emit_approx_sqrt created a pseudo
    register that it never used.
    
    2020-02-21  Richard Sandiford  <richard.sandiford@arm.com>
    
    gcc/
            * config/aarch64/aarch64.c (aarch64_emit_approx_sqrt): Don't create
            an unused xmsk register when handling approximate rsqrt.

Diff:
---
 gcc/ChangeLog                |  5 +++++
 gcc/config/aarch64/aarch64.c | 17 ++++++++++-------
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 16a23d00944..8241af4fbef 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2020-02-21  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* config/aarch64/aarch64.c (aarch64_emit_approx_sqrt): Don't create
+	an unused xmsk register when handling approximate rsqrt.
+
 2020-02-21  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* config/aarch64/aarch64.c (aarch64_emit_approx_sqrt): Fix inverted
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 6fb567ae4bf..0acaa06b91c 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -12774,14 +12774,17 @@ aarch64_emit_approx_sqrt (rtx dst, rtx src, bool recp)
   machine_mode mmsk = (VECTOR_MODE_P (mode)
 		       ? related_int_vector_mode (mode).require ()
 		       : int_mode_for_mode (mode).require ());
-  rtx xmsk = gen_reg_rtx (mmsk);
+  rtx xmsk = NULL_RTX;
   if (!recp)
-    /* When calculating the approximate square root, compare the
-       argument with 0.0 and create a mask.  */
-    emit_insn (gen_rtx_SET (xmsk,
-			    gen_rtx_NEG (mmsk,
-					 gen_rtx_EQ (mmsk, src,
-						     CONST0_RTX (mode)))));
+    {
+      /* When calculating the approximate square root, compare the
+	 argument with 0.0 and create a mask.  */
+      xmsk = gen_reg_rtx (mmsk);
+      emit_insn (gen_rtx_SET (xmsk,
+			      gen_rtx_NEG (mmsk,
+					   gen_rtx_EQ (mmsk, src,
+						       CONST0_RTX (mode)))));
+    }
 
   /* Estimate the approximate reciprocal square root.  */
   rtx xdst = gen_reg_rtx (mode);