Merge pull request #2372 from LemonBoy/aeabi_idiv

compiler-rt: Add __divsi3, __aeabi_idiv

1 files changed, 81 insertions, 1 deletions

diff --git a/std/special/compiler_rt.zig b/std/special/compiler_rt.zig
index 6a0f832047..d6af9535d7 100644
--- a/std/special/compiler_rt.zig
+++ b/std/special/compiler_rt.zig
@@ -102,9 +102,11 @@ comptime {
     @export("__udivmoddi4", @import("compiler_rt/udivmoddi4.zig").__udivmoddi4, linkage);
     @export("__popcountdi2", @import("compiler_rt/popcountdi2.zig").__popcountdi2, linkage);
 
+    @export("__divsi3", __divsi3, linkage);
     @export("__udivsi3", __udivsi3, linkage);
     @export("__udivdi3", __udivdi3, linkage);
     @export("__umoddi3", __umoddi3, linkage);
+    @export("__divmodsi4", __divmodsi4, linkage);
     @export("__udivmodsi4", __udivmodsi4, linkage);
 
     @export("__negsf2", @import("compiler_rt/negXf2.zig").__negsf2, linkage);
@@ -112,8 +114,11 @@ comptime {
 
     if (is_arm_arch and !is_arm_64) {
         @export("__aeabi_uldivmod", __aeabi_uldivmod, linkage);
-        @export("__aeabi_uidivmod", __aeabi_uidivmod, linkage);
+
+        @export("__aeabi_idiv", __divsi3, linkage);
+        @export("__aeabi_idivmod", __divmodsi4, linkage);
         @export("__aeabi_uidiv", __udivsi3, linkage);
+        @export("__aeabi_uidivmod", __aeabi_uidivmod, linkage);
 
         @export("__aeabi_memcpy", __aeabi_memcpy, linkage);
         @export("__aeabi_memcpy4", __aeabi_memcpy, linkage);
@@ -558,6 +563,14 @@ nakedcc fn ___chkstk_ms() align(4) void {
     );
 }
 
+extern fn __divmodsi4(a: i32, b: i32, rem: *i32) i32 {
+    @setRuntimeSafety(is_test);
+
+    const d = __divsi3(a, b);
+    rem.* = a -% (d * b);
+    return d;
+}
+
 extern fn __udivmodsi4(a: u32, b: u32, rem: *u32) u32 {
     @setRuntimeSafety(is_test);
 
@@ -566,6 +579,20 @@ extern fn __udivmodsi4(a: u32, b: u32, rem: *u32) u32 {
     return d;
 }
 
+extern fn __divsi3(n: i32, d: i32) i32 {
+    @setRuntimeSafety(is_test);
+
+    // Set aside the sign of the quotient.
+    const sign = @bitCast(u32, (n ^ d) >> 31);
+    // Take absolute value of a and b via abs(x) = (x^(x >> 31)) - (x >> 31).
+    const abs_n = (n ^ (n >> 31)) -% (n >> 31);
+    const abs_d = (d ^ (d >> 31)) -% (d >> 31);
+    // abs(a) / abs(b)
+    const res = @bitCast(u32, abs_n) / @bitCast(u32, abs_d);
+    // Apply sign of quotient to result and return.
+    return @bitCast(i32, (res ^ sign) -% sign);
+}
+
 extern fn __udivsi3(n: u32, d: u32) u32 {
     @setRuntimeSafety(is_test);
 
@@ -1293,3 +1320,56 @@ fn test_one_udivsi3(a: u32, b: u32, expected_q: u32) void {
     const q: u32 = __udivsi3(a, b);
     testing.expect(q == expected_q);
 }
+
+test "test_divsi3" {
+    const cases = [][3]i32{
+        []i32{ 0,  1,  0},
+        []i32{ 0, -1,  0},
+        []i32{ 2,  1,  2},
+        []i32{ 2, -1, -2},
+        []i32{-2,  1, -2},
+        []i32{-2, -1,  2},
+
+        []i32{@bitCast(i32, u32(0x80000000)),  1, @bitCast(i32, u32(0x80000000))},
+        []i32{@bitCast(i32, u32(0x80000000)), -1, @bitCast(i32, u32(0x80000000))},
+        []i32{@bitCast(i32, u32(0x80000000)), -2, 0x40000000},
+        []i32{@bitCast(i32, u32(0x80000000)),  2, @bitCast(i32, u32(0xC0000000))},
+    };
+
+    for (cases) |case| {
+        test_one_divsi3(case[0], case[1], case[2]);
+    }
+}
+
+fn test_one_divsi3(a: i32, b: i32, expected_q: i32) void {
+    const q: i32 = __divsi3(a, b);
+    testing.expect(q == expected_q);
+}
+
+test "test_divmodsi4" {
+    const cases = [][4]i32{
+        []i32{ 0,  1,  0,  0},
+        []i32{ 0, -1,  0,  0},
+        []i32{ 2,  1,  2,  0},
+        []i32{ 2, -1, -2,  0},
+        []i32{-2,  1, -2,  0},
+        []i32{-2, -1,  2,  0},
+        []i32{ 7,  5,  1,  2},
+        []i32{-7,  5, -1, -2},
+        []i32{19,  5,  3,  4},
+        []i32{19, -5, -3,  4},
+
+        []i32{@bitCast(i32, u32(0x80000000)), 8, @bitCast(i32, u32(0xf0000000)), 0},
+        []i32{@bitCast(i32, u32(0x80000007)), 8, @bitCast(i32, u32(0xf0000001)), -1},
+    };
+
+    for (cases) |case| {
+        test_one_divmodsi4(case[0], case[1], case[2], case[3]);
+    }
+}
+
+fn test_one_divmodsi4(a: i32, b: i32, expected_q: i32, expected_r: i32) void {
+    var r: i32 = undefined;
+    const q: i32 = __divmodsi4(a, b, &r);
+    testing.expect(q == expected_q and r == expected_r);
+}