diff --git a/core/runtime/internal.odin b/core/runtime/internal.odin
index 5bb0f18de..13191e07c 100644
--- a/core/runtime/internal.odin
+++ b/core/runtime/internal.odin
@@ -672,3 +672,88 @@ gnu_f2h_ieee :: proc "c" (value: f32) -> u16 {
 extendhfsf2 :: proc "c" (value: u16) -> f32 {
 	return gnu_h2f_ieee(value);
 }
+
+
+
+@(link_name="__floattidf")
+floattidf :: proc(a: i128) -> f64 {
+	DBL_MANT_DIG :: 53;
+	if a == 0 {
+		return 0.0;
+	}
+	a := a;
+	N :: size_of(i128) * 8;
+	s := a >> (N-1);
+	a = (a ~ s) - s;
+	sd: = N - intrinsics.count_leading_zeros(a);  // number of significant digits
+	e := u32(sd - 1);        // exponent
+	if sd > DBL_MANT_DIG {
+		switch sd {
+		case DBL_MANT_DIG + 1:
+			a <<= 1;
+		case DBL_MANT_DIG + 2:
+			// okay
+		case:
+			a = i128(u128(a) >> u128(sd - (DBL_MANT_DIG+2))) |
+				i128(u128(a) & (~u128(0) >> u128(N + DBL_MANT_DIG+2 - sd)) != 0);
+		};
+
+		a |= i128((a & 4) != 0);
+		a += 1;
+		a >>= 2;
+
+		if a & (1 << DBL_MANT_DIG) != 0 {
+			a >>= 1;
+			e += 1;
+		}
+	} else {
+		a <<= u128(DBL_MANT_DIG - sd);
+	}
+	fb: [2]u32;
+	fb[1] = (u32(s) & 0x80000000) |           // sign
+	        ((e + 1023) << 20)    |           // exponent
+	        u32((u64(a) >> 32) & 0x000FFFFF); // mantissa-high
+	fb[1] = u32(a);                           // mantissa-low
+	return transmute(f64)fb;
+}
+
+
+@(link_name="__floattidf_unsigned")
+floattidf_unsigned :: proc(a: u128) -> f64 {
+	DBL_MANT_DIG :: 53;
+	if a == 0 {
+		return 0.0;
+	}
+	a := a;
+	N :: size_of(u128) * 8;
+	sd: = N - intrinsics.count_leading_zeros(a);  // number of significant digits
+	e := u32(sd - 1);        // exponent
+	if sd > DBL_MANT_DIG {
+		switch sd {
+		case DBL_MANT_DIG + 1:
+			a <<= 1;
+		case DBL_MANT_DIG + 2:
+			// okay
+		case:
+			a = u128(u128(a) >> u128(sd - (DBL_MANT_DIG+2))) |
+				u128(u128(a) & (~u128(0) >> u128(N + DBL_MANT_DIG+2 - sd)) != 0);
+		};
+
+		a |= u128((a & 4) != 0);
+		a += 1;
+		a >>= 2;
+
+		if a & (1 << DBL_MANT_DIG) != 0 {
+			a >>= 1;
+			e += 1;
+		}
+	} else {
+		a <<= u128(DBL_MANT_DIG - sd);
+	}
+	fb: [2]u32;
+	fb[1] = (0) |                             // sign
+	        ((e + 1023) << 20) |              // exponent
+	        u32((u64(a) >> 32) & 0x000FFFFF); // mantissa-high
+	fb[1] = u32(a);                           // mantissa-low
+	return transmute(f64)fb;
+}
diff --git a/core/runtime/internal_linux.odin b/core/runtime/internal_linux.odin
index 19b52a42a..ad46f55e8 100644
--- a/core/runtime/internal_linux.odin
+++ b/core/runtime/internal_linux.odin
@@ -87,45 +87,3 @@ fixdfti :: proc(a: u64) -> i128 {
 	}
 
 }
-
-@(link_name="__floattidf")
-floattidf :: proc(a: i128) -> f64 {
-	DBL_MANT_DIG :: 53;
-	if a == 0 {
-		return 0.0;
-	}
-	a := a;
-	N :: size_of(i128) * 8;
-	s := a >> (N-1);
-	a = (a ~ s) - s;
-	sd: = N - intrinsics.count_leading_zeros(a);  // number of significant digits
-	e := u32(sd - 1);        // exponent
-	if sd > DBL_MANT_DIG {
-		switch sd {
-		case DBL_MANT_DIG + 1:
-			a <<= 1;
-		case DBL_MANT_DIG + 2:
-			// okay
-		case:
-			a = i128(u128(a) >> u128(sd - (DBL_MANT_DIG+2))) |
-				i128(u128(a) & (~u128(0) >> u128(N + DBL_MANT_DIG+2 - sd)) != 0);
-		};
-
-		a |= i128((a & 4) != 0);
-		a += 1;
-		a >>= 2;
-
-		if a & (1 << DBL_MANT_DIG) != 0 {
-			a >>= 1;
-			e += 1;
-		}
-	} else {
-		a <<= u128(DBL_MANT_DIG - sd);
-	}
-	fb: [2]u32;
-	fb[1] = (u32(s) & 0x80000000) |           // sign
-	        ((e + 1023) << 20)    |           // exponent
-	        u32((u64(a) >> 32) & 0x000FFFFF); // mantissa-high
-	fb[1] = u32(a);                           // mantissa-low
-	return transmute(f64)fb;
-}
diff --git a/core/runtime/internal_windows.odin b/core/runtime/internal_windows.odin
index d7f00d155..2d3009eea 100644
--- a/core/runtime/internal_windows.odin
+++ b/core/runtime/internal_windows.odin
@@ -87,45 +87,3 @@ fixdfti :: proc(a: u64) -> i128 {
 	}
 
 }
-
-@(link_name="__floattidf")
-floattidf :: proc(a: i128) -> f64 {
-	DBL_MANT_DIG :: 53;
-	if a == 0 {
-		return 0.0;
-	}
-	a := a;
-	N :: size_of(i128) * 8;
-	s := a >> (N-1);
-	a = (a ~ s) - s;
-	sd: = N - intrinsics.count_leading_zeros(a);  // number of significant digits
-	e := u32(sd - 1);        // exponent
-	if sd > DBL_MANT_DIG {
-		switch sd {
-		case DBL_MANT_DIG + 1:
-			a <<= 1;
-		case DBL_MANT_DIG + 2:
-			// okay
-		case:
-			a = i128(u128(a) >> u128(sd - (DBL_MANT_DIG+2))) |
-				i128(u128(a) & (~u128(0) >> u128(N + DBL_MANT_DIG+2 - sd)) != 0);
-		};
-
-		a |= i128((a & 4) != 0);
-		a += 1;
-		a >>= 2;
-
-		if a & (1 << DBL_MANT_DIG) != 0 {
-			a >>= 1;
-			e += 1;
-		}
-	} else {
-		a <<= u128(DBL_MANT_DIG - sd);
-	}
-	fb: [2]u32;
-	fb[1] = (u32(s) & 0x80000000) |           // sign
-	        ((e + 1023) << 20)    |           // exponent
-	        u32((u64(a) >> 32) & 0x000FFFFF); // mantissa-high
-	fb[1] = u32(a);                           // mantissa-low
-	return transmute(f64)fb;
-}
diff --git a/src/checker.cpp b/src/checker.cpp
index 092d7bc31..2792bdece 100644
--- a/src/checker.cpp
+++ b/src/checker.cpp
@@ -1751,6 +1751,7 @@ void generate_minimum_dependency_set(Checker *c, Entity *start) {
 		str_lit("divti3"),
 		str_lit("fixdfti"),
 		str_lit("floattidf"),
+		str_lit("floattidf_unsigned"),
 		str_lit("truncsfhf2"),
 		str_lit("truncdfhf2"),
 		str_lit("gnu_h2f_ieee"),
diff --git a/src/llvm_backend.cpp b/src/llvm_backend.cpp
index 505d45b93..a4e6ddbe5 100644
--- a/src/llvm_backend.cpp
+++ b/src/llvm_backend.cpp
@@ -7821,6 +7821,17 @@ lbValue lb_emit_conv(lbProcedure *p, lbValue value, Type *t) {
 			return lb_emit_conv(p, res, t);
 		}
 
+		if (is_type_integer_128bit(src)) {
+			auto args = array_make<lbValue>(temporary_allocator(), 1);
+			args[0] = value;
+			char const *call = "floattidf";
+			if (is_type_unsigned(src)) {
+				call = "floattidf_unsigned";
+			}
+			lbValue res_f64 = lb_emit_runtime_call(p, call, args);
+			return lb_emit_conv(p, res_f64, t);
+		}
+
 		lbValue res = {};
 		res.type = t;
 		if (is_type_unsigned(src)) {