Add x86_tests

x86/x86_tests/README

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+This directory contains small unit tests used to develop an
+understanding of specific x86 instructions.
+
+It is not strictly needed for macaw-x86, but included when we need to
+revisit instruction semantics.

x86/x86_tests/ucomis/.gitignore

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+test_ucomis

x86/x86_tests/ucomis/Makefile

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+run : test_ucomis
+	./test_ucomis
+
+test_ucomis : test_ucomis.c
+	clang -o test_ucomis test_ucomis.c ucomis.s
+
+clean :
+	rm -rf test_ucomis
+
+.PHONY : run clean

x86/x86_tests/ucomis/test_ucomis.c

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+/*
+  This file contains some functionality tests to assess properties of the
+  ucomiss instruction.
+ */
+#include<stdbool.h>
+#include<stdint.h>
+#include<stdio.h>
+#include<stdlib.h>
+#include<stdarg.h>
+
+/* Perform a ucomis on the two inputs and return the flag register. */
+uint64_t do_ucomiss(float x, float y);
+
+uint64_t get_mxcsr();
+
+void set_mxcsr(uint64_t mxcsr);
+
+typedef union {
+    float f;
+    uint32_t i;
+} float_union;
+
+static
+float mk_float(uint32_t sign, uint8_t exp, uint32_t fraction) {
+    float_union s;
+    s.i = sign << 31 | exp << 23 | fraction;
+    return s.f;
+}
+
+// Return the exponent value of a float
+static
+uint8_t float_exp(float f) {
+    float_union s;
+    s.f = f;
+    return (s.i >> 23) & 0xff;
+}
+
+// Return the mantissa value of a float
+static
+uint8_t float_mantissa(float f) {
+    float_union s;
+    s.f = f;
+    return s.i & 0x7fffff;
+}
+
+static
+float mk_snan(uint32_t sign, uint32_t fraction) {
+    uint32_t mask = (1 << 22) - 1;
+    return mk_float(sign, 0xff, fraction & mask);
+}
+
+static
+float mk_qnan(uint32_t sign, uint32_t fraction) {
+    uint32_t mask = (1 << 22) - 1;
+    return mk_float(sign, 0xff, (1 << 22) | (fraction & mask));
+}
+
+// Return true if the floating point is a nan.
+static
+bool float_is_nan(float f) {
+    return (float_exp(f) == 0xff)
+	&& (float_mantissa(f) != 0);
+}
+
+uint32_t float_bits(float x) {
+    float_union s;
+    s.f = x;
+    return s.i;
+}
+
+bool get_cf(uint64_t flags) {
+    return (flags & 0x01) != 0;
+}
+
+bool get_pf(uint64_t flags) {
+    return (flags & 0x04) != 0;
+}
+
+bool get_zf(uint64_t flags) {
+    return (flags & 0x40) != 0;
+}
+
+void my_assert(bool b, const char* fmt, ...) {
+    if (!b) {
+	va_list args;
+	va_start(args, fmt);
+	vfprintf(stderr, fmt, args);
+	va_end(args);
+    }
+}
+
+int main(int argc, char** argv) {
+    set_mxcsr(0x1f01);
+
+    // test mk_float
+    if (mk_float(0, 127, 0) != 1.0) {
+	fprintf(stderr, "Unexpected float\n");
+	return -1;
+    }
+    if (mk_float(0, 128, 0) != 2.0) {
+	fprintf(stderr, "Unexpected float\n");
+	return -1;
+    }
+    if (mk_float(1, 128, 0) != -2.0) {
+	fprintf(stderr, "Unexpected float\n");
+	return -1;
+    }
+
+    float qnan = mk_qnan(0, 1);
+    if (float_bits(qnan) != 0x7fc00001) {
+	fprintf(stderr, "Unexpected float\n");
+	return -1;
+    }
+    if (!float_is_nan(qnan)) {
+	fprintf(stderr, "Unexpected float\n");
+	return -1;
+    }
+
+    // Test snan
+    float snan = mk_snan(0, 1);
+    if (float_bits(snan) != 0x7f800001) {
+	fprintf(stderr, "Unexpected float\n");
+	return -1;
+    }
+    if (!float_is_nan(snan)) {
+	fprintf(stderr, "Unexpected float\n");
+	return -1;
+    }
+
+    uint64_t r = do_ucomiss(0, 1);
+    my_assert( get_cf(r), "Unexpected cf ucomiss(0,1)");
+    my_assert(!get_pf(r), "Unexpected pf ucomiss(0,1)");
+    my_assert(!get_zf(r), "Unexpected zf ucomiss(0,1)");
+
+    r = do_ucomiss(1, 0);
+    my_assert(!get_cf(r), "Unexpected cf ucomiss(1,0)");
+    my_assert(!get_pf(r), "Unexpected pf ucomiss(1,0)");
+    my_assert(!get_zf(r), "Unexpected zf ucomiss(1,0)");
+
+    r = do_ucomiss(1, 1);
+    my_assert(!get_cf(r), "Unexpected cf ucomiss(1,1)");
+    my_assert(!get_pf(r), "Unexpected pf ucomiss(1,1)");
+    my_assert( get_zf(r), "Unexpected zf ucomiss(1,1)");
+
+    return 0;
+}

x86/x86_tests/ucomis/ucomis.s

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+.intel_syntax noprefix
+.section __TEXT,__text
+
+.global _do_ucomiss
+_do_ucomiss:
+	mov rax, 0
+	push rax
+	popfq
+	ucomiss xmm0, xmm1
+	pushfq
+	pop rax
+	ret
+
+.global _get_mxcsr
+_get_mxcsr:
+	push rax
+	stmxcsr [rsp]
+	pop rax
+	ret
+.global _set_mxcsr
+_set_mxcsr:
+	push rdi
+	ldmxcsr [rsp]
+	pop rdi
+	ret