Hi,
This patch adds the half-to-double conversions, both as library functions,
or when supported in hardware, using the appropriate instructions.
That means adding support for the __gnu_d2h_{ieee/alternative} library calls
added in patch 2/4, and providing a more aggressive truncdfhf2 where we can.
This also lets us remove the implementation of TARGET_CONVERT_TO_TYPE.
Bootstrapped on an ARMv8-A machine,and crosstested with no issues.
OK?
Thanks,
James
---
gcc/
2016-11-09 James Greenhalgh <james.greenha...@arm.com>
* config/arm/arm.c (arm_convert_to_type): Delete.
(TARGET_CONVERT_TO_TYPE): Delete.
(arm_init_libfuncs): Enable trunc_optab from DFmode to HFmode.
(arm_libcall_uses_aapcs_base): Add trunc_optab from DF- to HFmode.
* config/arm/arm.h (TARGET_FP16_TO_DOUBLE): New.
* config/arm/arm.md (truncdfhf2): Only convert through SFmode if we
are in fast math mode, and have no single step hardware instruction.
(extendhfdf2): Only expand through SFmode if we don't have a
single-step hardware instruction.
* config/arm/vfp.md (*truncdfhf2): New.
(extendhfdf2): Likewise.
gcc/testsuite/
2016-11-09 James Greenhalgh <james.greenha...@arm.com>
* gcc.target/arm/fp16-rounding-alt-1.c (ROUNDED): Change expected
result.
* gcc.target/arm/fp16-rounding-ieee-1.c (ROUNDED): Change expected
result.
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 239117f..b9097c5 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -245,7 +245,6 @@ static bool arm_output_addr_const_extra (FILE *, rtx);
static bool arm_allocate_stack_slots_for_args (void);
static bool arm_warn_func_return (tree);
static tree arm_promoted_type (const_tree t);
-static tree arm_convert_to_type (tree type, tree expr);
static bool arm_scalar_mode_supported_p (machine_mode);
static bool arm_frame_pointer_required (void);
static bool arm_can_eliminate (const int, const int);
@@ -654,9 +653,6 @@ static const struct attribute_spec arm_attribute_table[] =
#undef TARGET_PROMOTED_TYPE
#define TARGET_PROMOTED_TYPE arm_promoted_type
-#undef TARGET_CONVERT_TO_TYPE
-#define TARGET_CONVERT_TO_TYPE arm_convert_to_type
-
#undef TARGET_SCALAR_MODE_SUPPORTED_P
#define TARGET_SCALAR_MODE_SUPPORTED_P arm_scalar_mode_supported_p
@@ -2535,6 +2531,11 @@ arm_init_libfuncs (void)
? "__gnu_h2f_ieee"
: "__gnu_h2f_alternative"));
+ set_conv_libfunc (trunc_optab, HFmode, DFmode,
+ (arm_fp16_format == ARM_FP16_FORMAT_IEEE
+ ? "__gnu_d2h_ieee"
+ : "__gnu_d2h_alternative"));
+
/* Arithmetic. */
set_optab_libfunc (add_optab, HFmode, NULL);
set_optab_libfunc (sdiv_optab, HFmode, NULL);
@@ -5262,6 +5263,8 @@ arm_libcall_uses_aapcs_base (const_rtx libcall)
SFmode));
add_libcall (libcall_htab, convert_optab_libfunc (trunc_optab, SFmode,
DFmode));
+ add_libcall (libcall_htab,
+ convert_optab_libfunc (trunc_optab, HFmode, DFmode));
}
return libcall && libcall_htab->find (libcall) != NULL;
@@ -22517,23 +22520,6 @@ arm_promoted_type (const_tree t)
return NULL_TREE;
}
-/* Implement TARGET_CONVERT_TO_TYPE.
- Specifically, this hook implements the peculiarity of the ARM
- half-precision floating-point C semantics that requires conversions between
- __fp16 to or from double to do an intermediate conversion to float. */
-
-static tree
-arm_convert_to_type (tree type, tree expr)
-{
- tree fromtype = TREE_TYPE (expr);
- if (!SCALAR_FLOAT_TYPE_P (fromtype) || !SCALAR_FLOAT_TYPE_P (type))
- return NULL_TREE;
- if ((TYPE_PRECISION (fromtype) == 16 && TYPE_PRECISION (type) > 32)
- || (TYPE_PRECISION (type) == 16 && TYPE_PRECISION (fromtype) > 32))
- return convert (type, convert (float_type_node, expr));
- return NULL_TREE;
-}
-
/* Implement TARGET_SCALAR_MODE_SUPPORTED_P.
This simply adds HFmode as a supported mode; even though we don't
implement arithmetic on this type directly, it's supported by
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index c8d7462..e759720 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -179,6 +179,11 @@ extern void (*arm_lang_output_object_attributes_hook)(void);
#define TARGET_FP16 \
(ARM_FPU_FSET_HAS (TARGET_FPU_FEATURES, FPU_FL_FP16))
+/* FPU supports converting between HFmode and DFmode in a single hardware
+ step. */
+#define TARGET_FP16_TO_DOUBLE \
+ (TARGET_HARD_FLOAT && (TARGET_FP16 && TARGET_VFP5))
+
/* FPU supports fused-multiply-add operations. */
#define TARGET_FMA (TARGET_FPU_REV >= 4)
diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index 8393f65..4074773 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -5177,20 +5177,35 @@
""
)
-;; DFmode to HFmode conversions have to go through SFmode.
+;; DFmode to HFmode conversions on targets without a single-step hardware
+;; instruction for it would have to go through SFmode. This is dangerous
+;; as it introduces double rounding.
+;;
+;; Disable this pattern unless we are in an unsafe math mode, or we have
+;; a single-step instruction.
+
(define_expand "truncdfhf2"
- [(set (match_operand:HF 0 "general_operand" "")
+ [(set (match_operand:HF 0 "s_register_operand" "")
(float_truncate:HF
- (match_operand:DF 1 "general_operand" "")))]
- "TARGET_EITHER"
- "
- {
- rtx op1;
- op1 = convert_to_mode (SFmode, operands[1], 0);
- op1 = convert_to_mode (HFmode, op1, 0);
- emit_move_insn (operands[0], op1);
- DONE;
- }"
+ (match_operand:DF 1 "s_register_operand" "")))]
+ "(TARGET_EITHER && flag_unsafe_math_optimizations)
+ || (TARGET_32BIT && TARGET_FP16_TO_DOUBLE)"
+{
+ /* We don't have a direct instruction for this, so we must be in
+ an unsafe math mode, and going via SFmode. */
+
+ if (!(TARGET_32BIT && TARGET_FP16_TO_DOUBLE))
+ {
+ rtx op1;
+ gcc_assert (flag_unsafe_math_optimizations);
+ op1 = convert_to_mode (SFmode, operands[1], 0);
+ op1 = convert_to_mode (HFmode, op1, 0);
+ emit_move_insn (operands[0], op1);
+ DONE;
+ }
+ /* Otherwise, we will pick this up as a single instruction with
+ no intermediary rounding. */
+}
)
;; Zero and sign extension instructions.
@@ -5684,19 +5699,28 @@
""
)
-;; HFmode -> DFmode conversions have to go through SFmode.
+;; HFmode -> DFmode conversions where we don't have an instruction for it
+;; must go through SFmode.
+;;
+;; This is always safe for an extend.
+
(define_expand "extendhfdf2"
- [(set (match_operand:DF 0 "general_operand" "")
- (float_extend:DF (match_operand:HF 1 "general_operand" "")))]
+ [(set (match_operand:DF 0 "s_register_operand" "")
+ (float_extend:DF (match_operand:HF 1 "s_register_operand" "")))]
"TARGET_EITHER"
- "
- {
- rtx op1;
- op1 = convert_to_mode (SFmode, operands[1], 0);
- op1 = convert_to_mode (DFmode, op1, 0);
- emit_insn (gen_movdf (operands[0], op1));
- DONE;
- }"
+{
+ /* We don't have a direct instruction for this, so go via SFmode. */
+ if (!(TARGET_32BIT && TARGET_FP16_TO_DOUBLE))
+ {
+ rtx op1;
+ op1 = convert_to_mode (SFmode, operands[1], 0);
+ op1 = convert_to_mode (DFmode, op1, 0);
+ emit_insn (gen_movdf (operands[0], op1));
+ DONE;
+ }
+ /* Otherwise, we're done producing RTL and will pick up the correct
+ pattern to do this with one rounding-step in a single instruction. */
+}
)
;; Move insns (including loads and stores)
diff --git a/gcc/config/arm/vfp.md b/gcc/config/arm/vfp.md
index 2051f10..d417e92 100644
--- a/gcc/config/arm/vfp.md
+++ b/gcc/config/arm/vfp.md
@@ -1507,6 +1507,26 @@
(set_attr "type" "f_cvt")]
)
+(define_insn "*truncdfhf2"
+ [(set (match_operand:HF 0 "s_register_operand" "=t")
+ (float_truncate:HF (match_operand:DF 1 "s_register_operand" "w")))]
+ "TARGET_32BIT && TARGET_FP16_TO_DOUBLE"
+ "vcvtb%?.f16.f64\\t%0, %P1"
+ [(set_attr "predicable" "yes")
+ (set_attr "predicable_short_it" "no")
+ (set_attr "type" "f_cvt")]
+)
+
+(define_insn "*extendhfdf2"
+ [(set (match_operand:DF 0 "s_register_operand" "=w")
+ (float_extend:DF (match_operand:HF 1 "s_register_operand" "t")))]
+ "TARGET_32BIT && TARGET_FP16_TO_DOUBLE"
+ "vcvtb%?.f64.f16\\t%P0, %1"
+ [(set_attr "predicable" "yes")
+ (set_attr "predicable_short_it" "no")
+ (set_attr "type" "f_cvt")]
+)
+
(define_insn "truncsfhf2"
[(set (match_operand:HF 0 "s_register_operand" "=t")
(float_truncate:HF (match_operand:SF 1 "s_register_operand" "t")))]
diff --git a/gcc/testsuite/gcc.target/arm/fp16-rounding-alt-1.c b/gcc/testsuite/gcc.target/arm/fp16-rounding-alt-1.c
index 1c15b61..27bb40d 100644
--- a/gcc/testsuite/gcc.target/arm/fp16-rounding-alt-1.c
+++ b/gcc/testsuite/gcc.target/arm/fp16-rounding-alt-1.c
@@ -1,6 +1,6 @@
-/* Test intermediate rounding of double to float and then to __fp16, using
- an example of a number that would round differently if it went directly
- from double to __fp16. */
+/* Test that rounding double to __fp16 happens directly, using an example
+ of a number that would round differently if it went from double to
+ __fp16 via float. */
/* { dg-do run } */
/* { dg-require-effective-target arm_fp16_alternative_ok } */
@@ -11,8 +11,8 @@
/* The original double value. */
#define ORIG 0x1.0020008p0
-/* The expected (double)((__fp16)((float)ORIG)) value. */
-#define ROUNDED 0x1.0000000p0
+/* The expected (double)((__fp16)ORIG) value. */
+#define ROUNDED 0x1.0040000p0
typedef union u {
__fp16 f;
diff --git a/gcc/testsuite/gcc.target/arm/fp16-rounding-ieee-1.c b/gcc/testsuite/gcc.target/arm/fp16-rounding-ieee-1.c
index 866d4d8..194dc9d 100644
--- a/gcc/testsuite/gcc.target/arm/fp16-rounding-ieee-1.c
+++ b/gcc/testsuite/gcc.target/arm/fp16-rounding-ieee-1.c
@@ -1,6 +1,6 @@
-/* Test intermediate rounding of double to float and then to __fp16, using
- an example of a number that would round differently if it went directly
- from double to __fp16. */
+/* Test that rounding double to __fp16 happens directly, using an example
+ of a number that would round differently if it went from double to
+ __fp16 via float. */
/* { dg-do run } */
/* { dg-options "-mfp16-format=ieee" } */
@@ -10,8 +10,8 @@
/* The original double value. */
#define ORIG 0x1.0020008p0
-/* The expected (double)((__fp16)((float)ORIG)) value. */
-#define ROUNDED 0x1.0000000p0
+/* The expected (double)((__fp16)ORIG) value. */
+#define ROUNDED 0x1.0040000p0
typedef union u {
__fp16 f;
