[15/30,arm] Make -mfloat-abi=softfp work when there are no FPU instructions

Message ID 50a309e2716dc50e5527a34ad8429b88e41c7919.1497004220.git.Richard.Earnshaw@arm.com
State New
Headers show
Series
  • Reworking the -mcpu, -march and -mfpu options
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Commit Message

Richard Earnshaw (lists) June 9, 2017, 12:53 p.m.
Before this patch series it wasn't really possible to not have an FPU;
it was always there, even if the hardware didn't really support it.
Now that we have -mfpu=auto, the concept of not having an FPU becomes
real.  Consequently, when the -mfloat-abi switch is set to softfp
doing the Right Thing is much more important.  In this case we have a
soft-float ABI, but can use FP instructions if they are available.
To support this we have to separate out TARGET_HARD_FLOAT into two
use cases: one where the instructions exist and one when they don't.
We preserve the original meaning of TARGET_HARD_FLOAT (but add an extra
check) of meaning that we are generating HW FP instructions, and add a
new macro for the special case when use of FP instructions is permitted,
but might not be available at this time (the distinction is important
because they might be enabled by an attribute during the compilation).
TARGET_SOFT_FLOAT continues to be the exact inverse of TARGET_HARD_FLOAT,
but we now define it as such.

	* config/arm/arm.h (TARGET_HARD_FLOAT): Also check that we
	have some floating-point instructions.
	(TARGET_SOFT_FLOAT): Define as inverse of TARGET_HARD_FLOAT.
	(TARGET_MAYBE_HARD_FLOAT): New macro.
	* config/arm/arm-builtins.c (arm_init_builtins): Use
	TARGET_MAYBE_HARD_FLOAT.
	* config/arm/arm.c (arm_option_override): Use TARGET_HARD_FLOAT_ABI.
---
 gcc/config/arm/arm-builtins.c | 4 ++--
 gcc/config/arm/arm.c          | 3 +--
 gcc/config/arm/arm.h          | 9 +++++++--
 3 files changed, 10 insertions(+), 6 deletions(-)

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diff --git a/gcc/config/arm/arm-builtins.c b/gcc/config/arm/arm-builtins.c
index a0569ed..9755189 100644
--- a/gcc/config/arm/arm-builtins.c
+++ b/gcc/config/arm/arm-builtins.c
@@ -1876,7 +1876,7 @@  arm_init_builtins (void)
      arm_init_neon_builtins which uses it.  */
   arm_init_fp16_builtins ();
 
-  if (TARGET_HARD_FLOAT)
+  if (TARGET_MAYBE_HARD_FLOAT)
     {
       arm_init_neon_builtins ();
       arm_init_vfp_builtins ();
@@ -1885,7 +1885,7 @@  arm_init_builtins (void)
 
   arm_init_acle_builtins ();
 
-  if (TARGET_HARD_FLOAT)
+  if (TARGET_MAYBE_HARD_FLOAT)
     {
       tree ftype_set_fpscr
 	= build_function_type_list (void_type_node, unsigned_type_node, NULL);
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 7296ad3..97d2fbd 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -3467,8 +3467,7 @@  arm_option_override (void)
     {
       if (arm_abi == ARM_ABI_IWMMXT)
 	arm_pcs_default = ARM_PCS_AAPCS_IWMMXT;
-      else if (arm_float_abi == ARM_FLOAT_ABI_HARD
-	       && TARGET_HARD_FLOAT)
+      else if (TARGET_HARD_FLOAT_ABI)
 	{
 	  arm_pcs_default = ARM_PCS_AAPCS_VFP;
 	  if (!bitmap_bit_p (arm_active_target.isa, isa_bit_VFPv2))
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index dea3d0a..570bcd7 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -119,9 +119,14 @@  extern tree arm_fp16_type_node;
 #define TARGET_32BIT_P(flags)  (TARGET_ARM_P (flags) || TARGET_THUMB2_P (flags))
 
 /* Run-time Target Specification.  */
-#define TARGET_SOFT_FLOAT		(arm_float_abi == ARM_FLOAT_ABI_SOFT)
 /* Use hardware floating point instructions. */
-#define TARGET_HARD_FLOAT		(arm_float_abi != ARM_FLOAT_ABI_SOFT)
+#define TARGET_HARD_FLOAT	(arm_float_abi != ARM_FLOAT_ABI_SOFT	\
+				 && bitmap_bit_p (arm_active_target.isa, \
+						  isa_bit_VFPv2))
+#define TARGET_SOFT_FLOAT	(!TARGET_HARD_FLOAT)
+/* User has permitted use of FP instructions, if they exist for this
+   target.  */
+#define TARGET_MAYBE_HARD_FLOAT (arm_float_abi != ARM_FLOAT_ABI_SOFT)
 /* Use hardware floating point calling convention.  */
 #define TARGET_HARD_FLOAT_ABI		(arm_float_abi == ARM_FLOAT_ABI_HARD)
 #define TARGET_IWMMXT			(arm_arch_iwmmxt)