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ffi: fix float passing in libffi for riscv64 #63976

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ffi: fix float passing in libffi for riscv64 #63976

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58 changes: 46 additions & 12 deletions deps/libffi/src/riscv/ffi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,10 +35,15 @@

#if __riscv_float_abi_double
#define ABI_FLEN 64
#define ABI_FLOAT double
typedef union {
uint64_t i;
double d;
} float_reg;
#elif __riscv_float_abi_single
#define ABI_FLEN 32
#define ABI_FLOAT float
typedef union {
float f;
} float_reg;
#endif

#define NARGREG 8
Expand All @@ -48,7 +53,7 @@
typedef struct call_context
{
#if ABI_FLEN
ABI_FLOAT fa[8];
float_reg fa[8];
#endif
size_t a[8];
/* used by the assembly code to in-place construct its own stack frame */
Expand Down Expand Up @@ -127,6 +132,30 @@ static float_struct_info struct_passed_as_elements(call_builder *cb, ffi_type *t

return ret;
}

#if ABI_FLEN >= 64
/* Float values in wider RISC-V FP registers are NaN-boxed */
static void marshal_float(call_builder *cb, void *data) {
union {
uint32_t i;
float f;
} value;

value.f = *(float *)data;
cb->aregs->fa[cb->used_float++].i =
UINT64_C(0xffffffff00000000) | value.i;
}

static void unmarshal_float(call_builder *cb, void *data) {
union {
uint32_t i;
float f;
} value;

value.i = (uint32_t)cb->aregs->fa[cb->used_float++].i;
*(float *)data = value.f;
}
#endif
#endif

/* allocates a single register, float register, or XLEN-sized stack slot to a datum */
Expand All @@ -146,17 +175,18 @@ static void marshal_atom(call_builder *cb, int type, void *data) {
#endif
case FFI_TYPE_POINTER: value = *(size_t *)data; break;

/* float values may be recoded in an implementation-defined way
by hardware conforming to 2.1 or earlier, so use asm to
reinterpret floats as doubles */
#if ABI_FLEN >= 32
#if ABI_FLEN >= 64
case FFI_TYPE_FLOAT:
marshal_float(cb, data);
return;
#elif ABI_FLEN >= 32
case FFI_TYPE_FLOAT:
asm("" : "=f"(cb->aregs->fa[cb->used_float++]) : "0"(*(float *)data));
asm("" : "=f"(cb->aregs->fa[cb->used_float++].f) : "0"(*(float *)data));
return;
#endif
#if ABI_FLEN >= 64
case FFI_TYPE_DOUBLE:
asm("" : "=f"(cb->aregs->fa[cb->used_float++]) : "0"(*(double *)data));
asm("" : "=f"(cb->aregs->fa[cb->used_float++].d) : "0"(*(double *)data));
return;
#endif
default: FFI_ASSERT(0); break;
Expand All @@ -172,14 +202,18 @@ static void marshal_atom(call_builder *cb, int type, void *data) {
static void unmarshal_atom(call_builder *cb, int type, void *data) {
size_t value;
switch (type) {
#if ABI_FLEN >= 32
#if ABI_FLEN >= 64
case FFI_TYPE_FLOAT:
unmarshal_float(cb, data);
return;
#elif ABI_FLEN >= 32
case FFI_TYPE_FLOAT:
asm("" : "=f"(*(float *)data) : "0"(cb->aregs->fa[cb->used_float++]));
asm("" : "=f"(*(float *)data) : "0"(cb->aregs->fa[cb->used_float++].f));
return;
#endif
#if ABI_FLEN >= 64
case FFI_TYPE_DOUBLE:
asm("" : "=f"(*(double *)data) : "0"(cb->aregs->fa[cb->used_float++]));
asm("" : "=f"(*(double *)data) : "0"(cb->aregs->fa[cb->used_float++].d));
return;
#endif
}
Expand Down
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