Use softfloat f80 for x87 fpu

This fixes several long-standing issues with x87 float emulation, in particular:

- 80 bit precision floats, fixing Haiku after its switch to musl libc (hrev53728)
- the precision bit in the x87 control word
- fucom and fucomi (unordered comparisons)
- aliasing of x87 and mmx registers
- rounding during conversion to integers

Operations that are not implemented in softfloat were implemented by
converting to f64 (sine, pow, ln, etc.) and thus operate with lower
precision.

Softfloat has been combined into a single file using a script [0] and checked into the repository.

[0] https://github.com/facebook/zstd/blob/57df21e2eb2e95053f63304f8f9b9bbf9ab7e3db/contrib/single_file_libs/combine.sh

Author: copy

Makefile

@@ -71,6 +71,7 @@ CARGO_FLAGS=\
 		-- \
 		-C linker=tools/rust-lld-wrapper \
 		-C link-args="--import-table --global-base=262144 $(STRIP_DEBUG_FLAG)" \
+		-C link-args="build/softfloat.o" \
 		--verbose
 
 CORE_FILES=const.js config.js io.js main.js lib.js ide.js pci.js floppy.js \
@@ -154,20 +155,26 @@ src/rust/gen/analyzer.rs: $(ANALYZER_DEPENDENCIES)
 src/rust/gen/analyzer0f.rs: $(ANALYZER_DEPENDENCIES)
 	./gen/generate_analyzer.js --output-dir build/ --table analyzer0f
 
-build/v86.wasm: $(RUST_FILES) Cargo.toml
+build/v86.wasm: $(RUST_FILES) build/softfloat.o Cargo.toml
 	mkdir -p build/
 	-ls -lh build/v86.wasm
 	cargo +nightly rustc --release $(CARGO_FLAGS)
 	mv build/wasm32-unknown-unknown/release/v86.wasm build/v86.wasm
 	ls -lh build/v86.wasm
 
-build/v86-debug.wasm: $(RUST_FILES) Cargo.toml
+build/v86-debug.wasm: $(RUST_FILES) build/softfloat.o Cargo.toml
 	mkdir -p build/
 	-ls -lh build/v86-debug.wasm
 	cargo +nightly rustc $(CARGO_FLAGS)
 	mv build/wasm32-unknown-unknown/debug/v86.wasm build/v86-debug.wasm
 	ls -lh build/v86-debug.wasm
 
+build/softfloat.o: lib/softfloat/softfloat.c
+	clang -c \
+	    --target=wasm32 -Os -flto -nostdlib -fvisibility=hidden -ffunction-sections -fdata-sections \
+	    -DSOFTFLOAT_FAST_INT64 -DINLINE_LEVEL=5 -DSOFTFLOAT_FAST_DIV32TO16 -DSOFTFLOAT_FAST_DIV64TO32 \
+	    -O2 -o build/softfloat.o lib/softfloat/softfloat.c
+
 clean:
 	-rm build/libv86.js
 	-rm build/libv86-debug.js
@@ -177,6 +184,7 @@ clean:
 	-rm $(INSTRUCTION_TABLES)
 	-rm build/*.map
 	-rm build/*.wast
+	-rm build/*.o
 	$(MAKE) -C $(NASM_TEST_DIR) clean
 
 run: