[Patch, GCC]Backporting r269039 to gcc8

[Delia Burduv]

Hi,

I am trying to backport r269039 to gcc8 wich solved this bug report: 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86487 . I have tested it on 
arm-none-linux-gnueabi,aarch64-none-linux-gnu and x86_64-pc-linux-gnu 
and there was no regression. The patch applied cleanly. I don't have 
commit rights, so if it is ok can someone please commit it for me?

Thanks,
Delia

gcc/ChangeLog:
2019-09-13  Delia Burduv  <delia.bur...@arm.com>

         Backport from trunk
         2019-02-20  Andre Vieira <andre.simoesdiasvie...@arm.com>

         PR target/86487
         * lra-constraints.c(uses_hard_regs_p): Fix handling of
         paradoxical SUBREGS.

gcc/testsuite/ChangeLog:
2019-09-13  Delia Burduv  <delia.bur...@arm.com>

         Backport from trunk
         2019-02-20  Andre Vieira <andre.simoesdiasvie...@arm.com>

         PR target/86487
         * gcc.target/arm/pr86487.c: New.


diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
index 484e9fa148c32208cd3af39e3aaa944069933ac0..1dea8c959d8f0e7e2d39f0ccf1b97aa1f64b024f 100644
--- a/gcc/lra-constraints.c
+++ b/gcc/lra-constraints.c
@@ -1774,14 +1774,24 @@ uses_hard_regs_p (rtx x, HARD_REG_SET set)
     return false;
   code = GET_CODE (x);
   mode = GET_MODE (x);
+
   if (code == SUBREG)
     {
+      /* For all SUBREGs we want to check whether the full multi-register
+	 overlaps the set.  For normal SUBREGs this means 'get_hard_regno' of
+	 the inner register, for paradoxical SUBREGs this means the
+	 'get_hard_regno' of the full SUBREG and for complete SUBREGs either is
+	 fine.  Use the wider mode for all cases.  */
+      rtx subreg = SUBREG_REG (x);
       mode = wider_subreg_mode (x);
-      x = SUBREG_REG (x);
-      code = GET_CODE (x);
+      if (mode == GET_MODE (subreg))
+	{
+	  x = subreg;
+	  code = GET_CODE (x);
+	}
     }
 
-  if (REG_P (x))
+  if (REG_P (x) || SUBREG_P (x))
     {
       x_hard_regno = get_hard_regno (x, true);
       return (x_hard_regno >= 0
diff --git a/gcc/testsuite/gcc.target/arm/pr86487.c b/gcc/testsuite/gcc.target/arm/pr86487.c
new file mode 100644
index 0000000000000000000000000000000000000000..1c1db7852d91a82a1d2b6eaa4f3d4c6dbef107f5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/pr86487.c
@@ -0,0 +1,10 @@
+/* { dg-skip-if "" { *-*-* } { "-march=armv[0-6]*" "-mthumb" } { "" } } */
+/* { dg-require-effective-target arm_neon_hw } */
+/* { dg-options "-O1 -mbig-endian" } */
+/* { dg-add-options arm_neon } */
+int a, b, c, d;
+long long fn1(long long p2) { return p2 == 0 ? -1 : -1 % p2; }
+void fn2(long long p1, short p2, long p3) {
+  b = fn1((d || 6) & a);
+  c = b | p3;
+}