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Simplify softfloat interface
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Currently the softfloat interface relies on two global registers defined in Sail to return values, one of which is a mirror of `fflags`. Unfortunately this doesn't work if the model is compiled with `-static` or wrapped in an anonymous namespace (I am doing the latter in a similar way to [@arichardson's method here](https://github.com/CTSRD-CHERI/cheri-compressed-cap/blob/89d21384c0183e5c422e23e1e5b37e127ad14e96/test/sail_wrapper_common.c#L50)).

This commit changes the design so that there is only a one-way dependency - the softfloat implementation does not depend on the model. This is done by returning the result of the floating point operation as a normal function return value, and then the model retrieves the new flags by simply calling another platform function (`extern_float_flags()`).

This is a bit cleaner, works with `-static` and also removes the need for `write_fflags()` and `update_softfloat_fflags()`.

Tested with `run_fp_tests.sh` - all 82 tests pass.
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@Timmmm
Timmmm committed Aug 4, 2023
1 parent 58cac61 commit 1093071
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403 changes: 136 additions & 267 deletions c_emulator/riscv_softfloat.c
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160 changes: 81 additions & 79 deletions c_emulator/riscv_softfloat.h
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Original file line number Diff line number Diff line change
@@ -1,85 +1,87 @@
#pragma once

unit softfloat_f16add(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f16sub(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f16mul(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f16div(mach_bits rm, mach_bits v1, mach_bits v2);

unit softfloat_f32add(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f32sub(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f32mul(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f32div(mach_bits rm, mach_bits v1, mach_bits v2);

unit softfloat_f64add(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f64sub(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f64mul(mach_bits rm, mach_bits v1, mach_bits v2);
unit softfloat_f64div(mach_bits rm, mach_bits v1, mach_bits v2);

unit softfloat_f16muladd(mach_bits rm, mach_bits v1, mach_bits v2,
mach_bits softfloat_float_flags(unit);

mach_bits softfloat_f16add(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f16sub(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f16mul(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f16div(mach_bits rm, mach_bits v1, mach_bits v2);

mach_bits softfloat_f32add(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f32sub(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f32mul(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f32div(mach_bits rm, mach_bits v1, mach_bits v2);

mach_bits softfloat_f64add(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f64sub(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f64mul(mach_bits rm, mach_bits v1, mach_bits v2);
mach_bits softfloat_f64div(mach_bits rm, mach_bits v1, mach_bits v2);

mach_bits softfloat_f16muladd(mach_bits rm, mach_bits v1, mach_bits v2,
mach_bits v3);
unit softfloat_f32muladd(mach_bits rm, mach_bits v1, mach_bits v2,
mach_bits softfloat_f32muladd(mach_bits rm, mach_bits v1, mach_bits v2,
mach_bits v3);
unit softfloat_f64muladd(mach_bits rm, mach_bits v1, mach_bits v2,
mach_bits softfloat_f64muladd(mach_bits rm, mach_bits v1, mach_bits v2,
mach_bits v3);

unit softfloat_f16sqrt(mach_bits rm, mach_bits v);
unit softfloat_f32sqrt(mach_bits rm, mach_bits v);
unit softfloat_f64sqrt(mach_bits rm, mach_bits v);

unit softfloat_f16toi32(mach_bits rm, mach_bits v);
unit softfloat_f16toui32(mach_bits rm, mach_bits v);
unit softfloat_f16toi64(mach_bits rm, mach_bits v);
unit softfloat_f16toui64(mach_bits rm, mach_bits v);

unit softfloat_f32toi32(mach_bits rm, mach_bits v);
unit softfloat_f32toui32(mach_bits rm, mach_bits v);
unit softfloat_f32toi64(mach_bits rm, mach_bits v);
unit softfloat_f32toui64(mach_bits rm, mach_bits v);

unit softfloat_f64toi32(mach_bits rm, mach_bits v);
unit softfloat_f64toui32(mach_bits rm, mach_bits v);
unit softfloat_f64toi64(mach_bits rm, mach_bits v);
unit softfloat_f64toui64(mach_bits rm, mach_bits v);

unit softfloat_i32tof16(mach_bits rm, mach_bits v);
unit softfloat_ui32tof16(mach_bits rm, mach_bits v);
unit softfloat_i64tof16(mach_bits rm, mach_bits v);
unit softfloat_ui64tof16(mach_bits rm, mach_bits v);

unit softfloat_i32tof32(mach_bits rm, mach_bits v);
unit softfloat_ui32tof32(mach_bits rm, mach_bits v);
unit softfloat_i64tof32(mach_bits rm, mach_bits v);
unit softfloat_ui64tof32(mach_bits rm, mach_bits v);

unit softfloat_i32tof64(mach_bits rm, mach_bits v);
unit softfloat_ui32tof64(mach_bits rm, mach_bits v);
unit softfloat_i64tof64(mach_bits rm, mach_bits v);
unit softfloat_ui64tof64(mach_bits rm, mach_bits v);

unit softfloat_f16tof32(mach_bits rm, mach_bits v);
unit softfloat_f16tof64(mach_bits rm, mach_bits v);
unit softfloat_f32tof64(mach_bits rm, mach_bits v);

unit softfloat_f32tof16(mach_bits rm, mach_bits v);
unit softfloat_f64tof16(mach_bits rm, mach_bits v);
unit softfloat_f64tof32(mach_bits rm, mach_bits v);

unit softfloat_f16lt(mach_bits v1, mach_bits v2);
unit softfloat_f16lt_quiet(mach_bits v1, mach_bits v2);
unit softfloat_f16le(mach_bits v1, mach_bits v2);
unit softfloat_f16le_quiet(mach_bits v1, mach_bits v2);
unit softfloat_f16eq(mach_bits v1, mach_bits v2);
unit softfloat_f32lt(mach_bits v1, mach_bits v2);
unit softfloat_f32lt_quiet(mach_bits v1, mach_bits v2);
unit softfloat_f32le(mach_bits v1, mach_bits v2);
unit softfloat_f32le_quiet(mach_bits v1, mach_bits v2);
unit softfloat_f32eq(mach_bits v1, mach_bits v2);
unit softfloat_f64lt(mach_bits v1, mach_bits v2);
unit softfloat_f64lt_quiet(mach_bits v1, mach_bits v2);
unit softfloat_f64le(mach_bits v1, mach_bits v2);
unit softfloat_f64le_quiet(mach_bits v1, mach_bits v2);
unit softfloat_f64eq(mach_bits v1, mach_bits v2);

unit softfloat_f16roundToInt(mach_bits rm, mach_bits v, bool exact);
unit softfloat_f32roundToInt(mach_bits rm, mach_bits v, bool exact);
unit softfloat_f64roundToInt(mach_bits rm, mach_bits v, bool exact);
mach_bits softfloat_f16sqrt(mach_bits rm, mach_bits v);
mach_bits softfloat_f32sqrt(mach_bits rm, mach_bits v);
mach_bits softfloat_f64sqrt(mach_bits rm, mach_bits v);

mach_bits softfloat_f16toi32(mach_bits rm, mach_bits v);
mach_bits softfloat_f16toui32(mach_bits rm, mach_bits v);
mach_bits softfloat_f16toi64(mach_bits rm, mach_bits v);
mach_bits softfloat_f16toui64(mach_bits rm, mach_bits v);

mach_bits softfloat_f32toi32(mach_bits rm, mach_bits v);
mach_bits softfloat_f32toui32(mach_bits rm, mach_bits v);
mach_bits softfloat_f32toi64(mach_bits rm, mach_bits v);
mach_bits softfloat_f32toui64(mach_bits rm, mach_bits v);

mach_bits softfloat_f64toi32(mach_bits rm, mach_bits v);
mach_bits softfloat_f64toui32(mach_bits rm, mach_bits v);
mach_bits softfloat_f64toi64(mach_bits rm, mach_bits v);
mach_bits softfloat_f64toui64(mach_bits rm, mach_bits v);

mach_bits softfloat_i32tof16(mach_bits rm, mach_bits v);
mach_bits softfloat_ui32tof16(mach_bits rm, mach_bits v);
mach_bits softfloat_i64tof16(mach_bits rm, mach_bits v);
mach_bits softfloat_ui64tof16(mach_bits rm, mach_bits v);

mach_bits softfloat_i32tof32(mach_bits rm, mach_bits v);
mach_bits softfloat_ui32tof32(mach_bits rm, mach_bits v);
mach_bits softfloat_i64tof32(mach_bits rm, mach_bits v);
mach_bits softfloat_ui64tof32(mach_bits rm, mach_bits v);

mach_bits softfloat_i32tof64(mach_bits rm, mach_bits v);
mach_bits softfloat_ui32tof64(mach_bits rm, mach_bits v);
mach_bits softfloat_i64tof64(mach_bits rm, mach_bits v);
mach_bits softfloat_ui64tof64(mach_bits rm, mach_bits v);

mach_bits softfloat_f16tof32(mach_bits rm, mach_bits v);
mach_bits softfloat_f16tof64(mach_bits rm, mach_bits v);
mach_bits softfloat_f32tof64(mach_bits rm, mach_bits v);

mach_bits softfloat_f32tof16(mach_bits rm, mach_bits v);
mach_bits softfloat_f64tof16(mach_bits rm, mach_bits v);
mach_bits softfloat_f64tof32(mach_bits rm, mach_bits v);

bool softfloat_f16lt(mach_bits v1, mach_bits v2);
bool softfloat_f16lt_quiet(mach_bits v1, mach_bits v2);
bool softfloat_f16le(mach_bits v1, mach_bits v2);
bool softfloat_f16le_quiet(mach_bits v1, mach_bits v2);
bool softfloat_f16eq(mach_bits v1, mach_bits v2);
bool softfloat_f32lt(mach_bits v1, mach_bits v2);
bool softfloat_f32lt_quiet(mach_bits v1, mach_bits v2);
bool softfloat_f32le(mach_bits v1, mach_bits v2);
bool softfloat_f32le_quiet(mach_bits v1, mach_bits v2);
bool softfloat_f32eq(mach_bits v1, mach_bits v2);
bool softfloat_f64lt(mach_bits v1, mach_bits v2);
bool softfloat_f64lt_quiet(mach_bits v1, mach_bits v2);
bool softfloat_f64le(mach_bits v1, mach_bits v2);
bool softfloat_f64le_quiet(mach_bits v1, mach_bits v2);
bool softfloat_f64eq(mach_bits v1, mach_bits v2);

mach_bits softfloat_f16roundToInt(mach_bits rm, mach_bits v, bool exact);
mach_bits softfloat_f32roundToInt(mach_bits rm, mach_bits v, bool exact);
mach_bits softfloat_f64roundToInt(mach_bits rm, mach_bits v, bool exact);
12 changes: 1 addition & 11 deletions model/riscv_fdext_regs.sail
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Original file line number Diff line number Diff line change
Expand Up @@ -528,26 +528,16 @@ val ext_write_fcsr : (bits(3), bits(5)) -> unit effect {rreg, wreg, escape}
function ext_write_fcsr (frm, fflags) = {
fcsr->FRM() = frm; /* Note: frm can be an illegal value, 101, 110, 111 */
fcsr->FFLAGS() = fflags;
update_softfloat_fflags(fflags);
dirty_fd_context_if_present();
}

/* called for softfloat paths (softfloat flags are consistent) */
val write_fflags : (bits(5)) -> unit effect {rreg, wreg, escape}
function write_fflags(fflags) = {
if fcsr.FFLAGS() != fflags
then dirty_fd_context_if_present();
fcsr->FFLAGS() = fflags;
}

/* called for non-softfloat paths (softfloat flags need updating) */
/* OR flags into the fflags register. */
val accrue_fflags : (bits(5)) -> unit effect {rreg, wreg, escape}
function accrue_fflags(flags) = {
let f = fcsr.FFLAGS() | flags;
if fcsr.FFLAGS() != f
then {
fcsr->FFLAGS() = f;
update_softfloat_fflags(f);
dirty_fd_context_if_present();
}
}
32 changes: 16 additions & 16 deletions model/riscv_insts_dext.sail
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Original file line number Diff line number Diff line change
Expand Up @@ -349,7 +349,7 @@ function clause execute (F_MADD_TYPE_D(rs3, rs2, rs1, rm, rd, op)) = {
FNMSUB_D => riscv_f64MulAdd (rm_3b, negate_D (rs1_val_64b), rs2_val_64b, rs3_val_64b),
FNMADD_D => riscv_f64MulAdd (rm_3b, negate_D (rs1_val_64b), rs2_val_64b, negate_D (rs3_val_64b))
};
write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_64b;
RETIRE_SUCCESS
}
Expand Down Expand Up @@ -413,7 +413,7 @@ function clause execute (F_BIN_RM_TYPE_D(rs2, rs1, rm, rd, op)) = {
FMUL_D => riscv_f64Mul (rm_3b, rs1_val_64b, rs2_val_64b),
FDIV_D => riscv_f64Div (rm_3b, rs1_val_64b, rs2_val_64b)
};
write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_64b;
RETIRE_SUCCESS
}
Expand Down Expand Up @@ -501,7 +501,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FSQRT_D)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_D) = riscv_f64Sqrt (rm_3b, rs1_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_D;
RETIRE_SUCCESS
}
Expand All @@ -516,7 +516,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_W_D)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_W) = riscv_f64ToI32 (rm_3b, rs1_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
X(rd) = sign_extend (rd_val_W);
RETIRE_SUCCESS
}
Expand All @@ -531,7 +531,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_WU_D)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_WU) = riscv_f64ToUi32 (rm_3b, rs1_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
X(rd) = sign_extend (rd_val_WU);
RETIRE_SUCCESS
}
Expand All @@ -546,7 +546,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_D_W)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_D) = riscv_i32ToF64 (rm_3b, rs1_val_W);

write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_D;
RETIRE_SUCCESS
}
Expand All @@ -561,7 +561,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_D_WU)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_D) = riscv_ui32ToF64 (rm_3b, rs1_val_WU);

write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_D;
RETIRE_SUCCESS
}
Expand All @@ -576,7 +576,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_S_D)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_S) = riscv_f64ToF32 (rm_3b, rs1_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_S(rd) = rd_val_S;
RETIRE_SUCCESS
}
Expand All @@ -591,7 +591,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_D_S)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_D) = riscv_f32ToF64 (rm_3b, rs1_val_S);

write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_D;
RETIRE_SUCCESS
}
Expand All @@ -607,7 +607,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_L_D)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_L) = riscv_f64ToI64 (rm_3b, rs1_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
X(rd) = sign_extend(rd_val_L);
RETIRE_SUCCESS
}
Expand All @@ -623,7 +623,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_LU_D)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_LU) = riscv_f64ToUi64 (rm_3b, rs1_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
X(rd) = sign_extend(rd_val_LU);
RETIRE_SUCCESS
}
Expand All @@ -639,7 +639,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_D_L)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_D) = riscv_i64ToF64 (rm_3b, rs1_val_L);

write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_D;
RETIRE_SUCCESS
}
Expand All @@ -655,7 +655,7 @@ function clause execute (F_UN_RM_TYPE_D(rs1, rm, rd, FCVT_D_LU)) = {
let rm_3b = encdec_rounding_mode(rm');
let (fflags, rd_val_D) = riscv_ui64ToF64 (rm_3b, rs1_val_LU);

write_fflags(fflags);
accrue_fflags(fflags);
F_or_X_D(rd) = rd_val_D;
RETIRE_SUCCESS
}
Expand Down Expand Up @@ -862,7 +862,7 @@ function clause execute (F_BIN_TYPE_D(rs2, rs1, rd, FEQ_D)) = {
let (fflags, rd_val) : (bits_fflags, bool) =
riscv_f64Eq (rs1_val_D, rs2_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
X(rd) = zero_extend(bool_to_bits(rd_val));
RETIRE_SUCCESS
}
Expand All @@ -874,7 +874,7 @@ function clause execute (F_BIN_TYPE_D(rs2, rs1, rd, FLT_D)) = {
let (fflags, rd_val) : (bits_fflags, bool) =
riscv_f64Lt (rs1_val_D, rs2_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
X(rd) = zero_extend(bool_to_bits(rd_val));
RETIRE_SUCCESS
}
Expand All @@ -886,7 +886,7 @@ function clause execute (F_BIN_TYPE_D(rs2, rs1, rd, FLE_D)) = {
let (fflags, rd_val) : (bits_fflags, bool) =
riscv_f64Le (rs1_val_D, rs2_val_D);

write_fflags(fflags);
accrue_fflags(fflags);
X(rd) = zero_extend(bool_to_bits(rd_val));
RETIRE_SUCCESS
}
Expand Down
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