[mono][mini] Fix conversion from r4/r8 to native u (#85964)

* [mono][mini] Fix conversion from r4/r8 to native u

When converting from float point to unsigned integer, we always do a conversion to u8, then do a simple integer conversion with range checks. The problem is that the first conversion to u8 pushes a STACK_I8 and doing a further conversion to u8 is not actually a nop since it will throw if the result of the previous conversion is negative.

* Enable tests

* [mono][jit] Reuse conv ovf methods used by interpreter

These follow CoreCLR implementation and don't rely on undefined behavior from out of range conversions.

src/libraries/System.Runtime/tests/System/UIntPtrTests.GenericMath.cs

@@ -1876,7 +1876,6 @@ public static void CreateCheckedFromDecimalTest()
         }
 
         [Fact]
-        [SkipOnMono("https://github.com/dotnet/runtime/issues/69794")]
         public static void CreateCheckedFromDoubleTest()
         {
             Assert.Equal((nuint)0x0000_0000, NumberBaseHelper<nuint>.CreateChecked<double>(+0.0));
@@ -2006,7 +2005,6 @@ public static void CreateCheckedFromIntPtrTest()
         }
 
         [Fact]
-        [SkipOnMono("https://github.com/dotnet/runtime/issues/69794")]
         public static void CreateCheckedFromNFloatTest()
         {
             Assert.Equal((nuint)0x0000_0000, NumberBaseHelper<nuint>.CreateChecked<NFloat>(0.0f));
@@ -2052,7 +2050,6 @@ public static void CreateCheckedFromSByteTest()
         }
 
         [Fact]
-        [SkipOnMono("https://github.com/dotnet/runtime/issues/69794")]
         public static void CreateCheckedFromSingleTest()
         {
             Assert.Equal((nuint)0x0000_0000, NumberBaseHelper<nuint>.CreateChecked<float>(+0.0f));

src/mono/mono/mini/jit-icalls.c

@@ -990,9 +990,8 @@ mono_rconv_u4 (float v)
 gint64
 mono_fconv_ovf_i8 (double v)
 {
-	const gint64 res = (gint64)v;
-
-	if (mono_isnan (v) || mono_trunc (v) != res) {
+	gint64 res;
+	if (!mono_try_trunc_i64 (v, &res)) {
 		ERROR_DECL (error);
 		mono_error_set_overflow (error);
 		mono_error_set_pending_exception (error);
@@ -1005,33 +1004,12 @@ guint64
 mono_fconv_ovf_u8 (double v)
 {
 	guint64 res;
-
-/*
- * The soft-float implementation of some ARM devices have a buggy guin64 to double
- * conversion that it looses precision even when the integer if fully representable
- * as a double.
- *
- * This was found with 4294967295ull, converting to double and back looses one bit of precision.
- *
- * To work around this issue we test for value boundaries instead.
- */
-#if defined(__arm__) && defined(MONO_ARCH_SOFT_FLOAT_FALLBACK)
-	if (mono_isnan (v) || !(v >= -0.5 && v <= ULLONG_MAX+0.5)) {
+	if (!mono_try_trunc_u64 (v, &res)) {
 		ERROR_DECL (error);
 		mono_error_set_overflow (error);
 		mono_error_set_pending_exception (error);
 		return 0;
 	}
-	res = (guint64)v;
-#else
-	res = (guint64)v;
-	if (mono_isnan (v) || mono_trunc (v) != res) {
-		ERROR_DECL (error);
-		mono_error_set_overflow (error);
-		mono_error_set_pending_exception (error);
-		return 0;
-	}
-#endif
 	return res;
 }
 
@@ -1046,9 +1024,8 @@ mono_rconv_i8 (float v)
 gint64
 mono_rconv_ovf_i8 (float v)
 {
-	const gint64 res = (gint64)v;
-
-	if (mono_isnan (v) || mono_trunc (v) != res) {
+	gint64 res;
+	if (!mono_try_trunc_i64 (v, &res)) {
 		ERROR_DECL (error);
 		mono_error_set_overflow (error);
 		mono_error_set_pending_exception (error);
@@ -1061,9 +1038,7 @@ guint64
 mono_rconv_ovf_u8 (float v)
 {
 	guint64 res;
-
-	res = (guint64)v;
-	if (mono_isnan (v) || mono_trunc (v) != res) {
+	if (!mono_try_trunc_u64 (v, &res)) {
 		ERROR_DECL (error);
 		mono_error_set_overflow (error);
 		mono_error_set_pending_exception (error);

src/mono/mono/mini/method-to-ir.c

@@ -8943,7 +8943,10 @@ mono_method_to_ir (MonoCompile *cfg, MonoMethod *method, MonoBasicBlock *start_b
 			if (sp [-1]->type == STACK_R8 || sp [-1]->type == STACK_R4) {
 				/* floats are always signed, _UN has no effect */
 				ADD_UNOP (CEE_CONV_OVF_U8);
-				ADD_UNOP (il_op);
+				if (TARGET_SIZEOF_VOID_P == 8 && il_op == MONO_CEE_CONV_OVF_U)
+					sp [-1]->type = STACK_PTR; // no additional conversion needed
+				else
+					ADD_UNOP (il_op);
 			} else {
 				ADD_UNOP (il_op);
 			}