https://gcc.gnu.org/g:3eeb4d88a51113e7099de67a53d0b7dd55e13c1c
commit 3eeb4d88a51113e7099de67a53d0b7dd55e13c1c
Author: Michael Meissner <meiss...@linux.ibm.com>
Date: Wed Aug 13 18:54:28 2025 -0400
Pass _Float16 arguments and return values in memory
2025-08-13 Michael Meissner <meiss...@linux.ibm.com>
gcc/
PR target/121525
* config/rs6000/rs6000-call.cc (rs6000_return_in_memory): Return
_Float16 values in memory unless -mno-ieee16-return-in-memory.
(rs6000_pass_by_reference): Pass _Float16 values by reference unless
-mno-ieee16-pass-by-reference.
* config/rs6000/rs6000.md (movhf): Make sure memory <- memory moves
are
not generated.
* config/rs6000/rs6000.opt (-mieee16-return-in-memory): New debug
option.
(-mieee16-pass-by-reference): Likewise.
Diff:
---
gcc/config/rs6000/rs6000-call.cc | 10 ++++++++++
gcc/config/rs6000/rs6000.md | 6 +++++-
gcc/config/rs6000/rs6000.opt | 8 ++++++++
3 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/gcc/config/rs6000/rs6000-call.cc b/gcc/config/rs6000/rs6000-call.cc
index 8fe5652442e3..d639519a4368 100644
--- a/gcc/config/rs6000/rs6000-call.cc
+++ b/gcc/config/rs6000/rs6000-call.cc
@@ -432,6 +432,11 @@ rs6000_discover_homogeneous_aggregate (machine_mode mode,
const_tree type,
bool
rs6000_return_in_memory (const_tree type, const_tree fntype ATTRIBUTE_UNUSED)
{
+ /* Because it is not covered by the ABI, return _Float16 (HFmode) in
+ memory. */
+ if (TYPE_MODE (type) == HFmode && TARGET_IEEE16_RETURN_IN_MEMORY)
+ return true;
+
/* We do not allow MMA types being used as return values. Only report
the invalid return value usage the first time we encounter it. */
if (cfun
@@ -1985,6 +1990,11 @@ rs6000_pass_by_reference (cumulative_args_t, const
function_arg_info &arg)
if (!arg.type)
return 0;
+ /* Because it is not covered by the ABI, pass _Float16 (HFmode) by
+ reference. */
+ if (arg.mode == HFmode && TARGET_IEEE16_PASS_BY_REFERENCE)
+ return true;
+
if (DEFAULT_ABI == ABI_V4 && TARGET_IEEEQUAD
&& FLOAT128_IEEE_P (TYPE_MODE (arg.type)))
{
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index b4af2eb4b9c0..a2f74245c42d 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -8149,7 +8149,11 @@
(define_expand "movhf"
[(set (match_operand:HF 0 "nonimmediate_operand")
(match_operand:HF 1 "any_operand"))]
- "TARGET_IEEE16")
+ "TARGET_IEEE16"
+{
+ if (MEM_P (operands[0]) && !REG_P (operands[1]))
+ operands[1] = force_reg (HFmode, operands[1]);
+})
;; On power10, we can load up HFmode constants with xxspltiw.
(define_insn "*movhf_xxspltiw"
diff --git a/gcc/config/rs6000/rs6000.opt b/gcc/config/rs6000/rs6000.opt
index 39ae7791c60a..8c6f08dc5c8f 100644
--- a/gcc/config/rs6000/rs6000.opt
+++ b/gcc/config/rs6000/rs6000.opt
@@ -642,6 +642,14 @@ mieee128-constant
Target Var(TARGET_IEEE128_CONSTANT) Init(1) Save
Generate (do not generate) code that uses the LXVKQ instruction.
+mieee16-return-in-memory
+Target Undocumented Var(TARGET_IEEE16_RETURN_IN_MEMORY) Init(1) Save
+Return _Float16 values in memory.
+
+mieee16-pass-by-reference
+Target Undocumented Var(TARGET_IEEE16_PASS_BY_REFERENCE) Init(1) Save
+Pass _Float16 by reference.
+
; Documented parameters
-param=rs6000-vect-unroll-limit=
