[PATCH, GCC/ARM] Fix PR85261: ICE with FPSCR setter builtin

[Thomas Preudhomme]

Instruction pattern for setting the FPSCR expects the input value to be
in a register. However, __builtin_arm_set_fpscr expander does not ensure
that this is the case and as a result GCC ICEs when the builtin is
called with a constant literal.

This commit fixes the builtin to force the input value into a register.
It also remove the unneeded volatile in the existing fpscr test and
fixes the function prototype.

ChangeLog entries are as follows:

*** gcc/ChangeLog ***

2018-04-06  Thomas Preud'homme  <thomas.preudho...@arm.com>

        PR target/85261
        * config/arm/arm-builtins.c (arm_expand_builtin): Force input operand
        into register.

*** gcc/testsuite/ChangeLog ***

2018-04-06  Thomas Preud'homme  <thomas.preudho...@arm.com>

        PR target/85261
        * gcc.target/arm/fpscr.c: Add call to __builtin_arm_set_fpscr with
        literal value.  Expect 2 MCR instruction.  Fix function prototype.
        Remove volatile keyword.

Testing: Built an arm-none-eabi GCC cross-compiler and testsuite shows
no regression.

Is this ok for stage4?

Best regards,

Thomas

diff --git a/gcc/config/arm/arm-builtins.c b/gcc/config/arm/arm-builtins.c
index 8940d1f6311bccf86664ab2eaa938735eec595f6..e100d933a77c5de4a13cb961d1bff40f57f2ea80 100644
--- a/gcc/config/arm/arm-builtins.c
+++ b/gcc/config/arm/arm-builtins.c
@@ -2592,7 +2592,7 @@ arm_expand_builtin (tree exp,
 	  icode = CODE_FOR_set_fpscr;
 	  arg0 = CALL_EXPR_ARG (exp, 0);
 	  op0 = expand_normal (arg0);
-	  pat = GEN_FCN (icode) (op0);
+	  pat = GEN_FCN (icode) (force_reg (SImode, op0));
 	}
       emit_insn (pat);
       return target;
diff --git a/gcc/testsuite/gcc.target/arm/fpscr.c b/gcc/testsuite/gcc.target/arm/fpscr.c
index 7b4d71d72d8964f6da0d0604bf59aeb4a895df43..4c3eaf7fcf75ad8582071ecb110fd1e4976a3b24 100644
--- a/gcc/testsuite/gcc.target/arm/fpscr.c
+++ b/gcc/testsuite/gcc.target/arm/fpscr.c
@@ -6,11 +6,14 @@
 /* { dg-add-options arm_fp } */
 
 void
-test_fpscr ()
+test_fpscr (void)
 {
-  volatile unsigned int status = __builtin_arm_get_fpscr ();
+  unsigned status;
+
+  __builtin_arm_set_fpscr (0);
+  status = __builtin_arm_get_fpscr ();
   __builtin_arm_set_fpscr (status);
 }
 
 /* { dg-final { scan-assembler "mrc\tp10, 7, r\[0-9\]+, cr1, cr0, 0" } } */
-/* { dg-final { scan-assembler "mcr\tp10, 7, r\[0-9\]+, cr1, cr0, 0" } } */
+/* { dg-final { scan-assembler-times "mcr\tp10, 7, r\[0-9\]+, cr1, cr0, 0" 2 } } */