[PATCH][committed][14 backport]AArch64: force operand to fresh register to avoid subreg issues [PR118892]

[Tamar Christina]

Hi All,

When the input is already a subreg and we try to make a paradoxical
subreg out of it for copysign this can fail if it violates the subreg
relationship.

Use force_lowpart_subreg instead of lowpart_subreg to then force the
results to a register instead of ICEing.

Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.

Committed to GCC-14

Thanks,
Tamar

gcc/ChangeLog:

        PR target/118892
        * config/aarch64/aarch64.md (copysign<GPF:mode>3): Use
        force_lowpart_subreg instead of lowpart_subreg.

gcc/testsuite/ChangeLog:

        PR target/118892
        * gcc.target/aarch64/copysign-pr118892.c: New test.

---
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 
95577b325cef9f6fd3f997c671935e28ef378e1a..6a481059bf086e923c1433d128b9b6a1182c615b
 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -7210,7 +7210,7 @@ (define_expand "copysign<GPF:mode>3"
 
       emit_insn (gen_iorv2<v_int_equiv>3 (
        lowpart_subreg (V2<V_INT_EQUIV>mode, operands[0], <MODE>mode),
-       lowpart_subreg (V2<V_INT_EQUIV>mode, operands[1], <MODE>mode),
+       force_lowpart_subreg (V2<V_INT_EQUIV>mode, operands[1], <MODE>mode),
        v_bitmask));
       DONE;
     }
diff --git a/gcc/testsuite/gcc.target/aarch64/copysign-pr118892.c 
b/gcc/testsuite/gcc.target/aarch64/copysign-pr118892.c
new file mode 100644
index 
0000000000000000000000000000000000000000..adfa30dc3e2db895af4f2057bdd1011fdb7d4537
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/copysign-pr118892.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast" } */
+
+double l();
+double f()
+{
+  double t6[2] = {l(), l()};
+  double t7[2];
+  __builtin_memcpy(&t7, &t6, sizeof(t6));
+  return -__builtin_fabs(t7[1]);
+}


-- 

diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 95577b325cef9f6fd3f997c671935e28ef378e1a..6a481059bf086e923c1433d128b9b6a1182c615b 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -7210,7 +7210,7 @@ (define_expand "copysign<GPF:mode>3"
 
       emit_insn (gen_iorv2<v_int_equiv>3 (
 	lowpart_subreg (V2<V_INT_EQUIV>mode, operands[0], <MODE>mode),
-	lowpart_subreg (V2<V_INT_EQUIV>mode, operands[1], <MODE>mode),
+	force_lowpart_subreg (V2<V_INT_EQUIV>mode, operands[1], <MODE>mode),
 	v_bitmask));
       DONE;
     }
diff --git a/gcc/testsuite/gcc.target/aarch64/copysign-pr118892.c b/gcc/testsuite/gcc.target/aarch64/copysign-pr118892.c
new file mode 100644
index 0000000000000000000000000000000000000000..adfa30dc3e2db895af4f2057bdd1011fdb7d4537
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/copysign-pr118892.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-Ofast" } */
+
+double l();
+double f()
+{
+  double t6[2] = {l(), l()};
+  double t7[2];
+  __builtin_memcpy(&t7, &t6, sizeof(t6));
+  return -__builtin_fabs(t7[1]);
+}