Merge pull request #14828 from jacobly0/fix-big-div

compiler_rt: fix rare case in udivei4

Author: andrewrk

lib/compiler_rt/udivmodei4.zig

@@ -79,16 +79,16 @@ fn divmod(q: ?[]u32, r: ?[]u32, u: []const u32, v: []const u32) !void {
             }
             break;
         }
-        var carry: u64 = 0;
+        var carry: i64 = 0;
         i = 0;
         while (i <= n) : (i += 1) {
             const p = qhat * limb(&vn, i);
             const t = limb(&un, i + j) - carry - @truncate(u32, p);
-            limb_set(&un, i + j, @truncate(u32, t));
-            carry = @intCast(u64, p >> 32) - @intCast(u64, t >> 32);
+            limb_set(&un, i + j, @truncate(u32, @bitCast(u64, t)));
+            carry = @intCast(i64, p >> 32) - @intCast(i64, t >> 32);
         }
-        const t = limb(&un, j + n + 1) - carry;
-        limb_set(&un, j + n + 1, @truncate(u32, t));
+        const t = limb(&un, j + n + 1) -% carry;
+        limb_set(&un, j + n + 1, @truncate(u32, @bitCast(u64, t)));
         if (q) |q_| limb_set(q_, j, @truncate(u32, qhat));
         if (t < 0) {
             if (q) |q_| limb_set(q_, j, limb(q_, j) - 1);
@@ -99,7 +99,7 @@ fn divmod(q: ?[]u32, r: ?[]u32, u: []const u32, v: []const u32) !void {
                 limb_set(&un, i + j, @truncate(u32, t2));
                 carry2 = t2 >> 32;
             }
-            limb_set(un, j + n + 1, @truncate(u32, limb(&un, j + n + 1) + carry2));
+            limb_set(&un, j + n + 1, @truncate(u32, limb(&un, j + n + 1) + carry2));
         }
         if (j == 0) break;
     }

lib/zig.h

@@ -190,10 +190,17 @@ typedef char bool;
 
 #if zig_has_builtin(trap)
 #define zig_trap() __builtin_trap()
+#elif _MSC_VER && (_M_IX86 || _M_X64)
+#define zig_trap() __ud2()
+#elif _MSC_VER
+#define zig_trap() __fastfail(0)
 #elif defined(__i386__) || defined(__x86_64__)
 #define zig_trap() __asm__ volatile("ud2");
+#elif defined(__arm__) || defined(__aarch64__)
+#define zig_breakpoint() __asm__ volatile("udf #0");
 #else
-#define zig_trap() raise(SIGTRAP)
+#include <stdlib.h>
+#define zig_trap() abort()
 #endif
 
 #if zig_has_builtin(debugtrap)
@@ -202,8 +209,17 @@ typedef char bool;
 #define zig_breakpoint() __debugbreak()
 #elif defined(__i386__) || defined(__x86_64__)
 #define zig_breakpoint() __asm__ volatile("int $0x03");
+#elif defined(__arm__)
+#define zig_breakpoint() __asm__ volatile("bkpt #0");
+#elif defined(__aarch64__)
+#define zig_breakpoint() __asm__ volatile("brk #0");
 #else
+#include <signal.h>
+#if defined(SIGTRAP)
 #define zig_breakpoint() raise(SIGTRAP)
+#else
+#define zig_breakpoint() zig_breakpoint_unavailable
+#endif
 #endif
 
 #if zig_has_builtin(return_address) || defined(zig_gnuc)
@@ -2384,6 +2400,44 @@ static inline void zig_subw_big(void *res, const void *lhs, const void *rhs, boo
     (void)zig_subo_big(res, lhs, rhs, is_signed, bits);
 }
 
+zig_extern void __udivei4(uint32_t *res, const uint32_t *lhs, const uint32_t *rhs, uintptr_t bits);
+static inline void zig_div_trunc_big(void *res, const void *lhs, const void *rhs, bool is_signed, uint16_t bits) {
+    if (!is_signed) {
+        __udivei4(res, lhs, rhs, bits);
+        return;
+    }
+
+    zig_trap();
+}
+
+static inline void zig_div_floor_big(void *res, const void *lhs, const void *rhs, bool is_signed, uint16_t bits) {
+    if (!is_signed) {
+        zig_div_trunc_big(res, lhs, rhs, is_signed, bits);
+        return;
+    }
+
+    zig_trap();
+}
+
+zig_extern void __umodei4(uint32_t *res, const uint32_t *lhs, const uint32_t *rhs, uintptr_t bits);
+static inline void zig_rem_big(void *res, const void *lhs, const void *rhs, bool is_signed, uint16_t bits) {
+    if (!is_signed) {
+        __umodei4(res, lhs, rhs, bits);
+        return;
+    }
+
+    zig_trap();
+}
+
+static inline void zig_mod_big(void *res, const void *lhs, const void *rhs, bool is_signed, uint16_t bits) {
+    if (!is_signed) {
+        zig_rem_big(res, lhs, rhs, is_signed, bits);
+        return;
+    }
+
+    zig_trap();
+}
+
 static inline uint16_t zig_clz_big(const void *val, bool is_signed, uint16_t bits) {
     const uint8_t *val_bytes = val;
     uint16_t byte_offset = 0;

src/codegen/c.zig

@@ -1885,25 +1885,28 @@ pub const DeclGen = struct {
     }
 
     fn renderBuiltinInfo(dg: *DeclGen, writer: anytype, ty: Type, info: BuiltinInfo) !void {
+        const cty = try dg.typeToCType(ty, .complete);
+        const is_big = cty.tag() == .array;
+
         switch (info) {
-            .none => {},
-            .bits => {
-                const target = dg.module.getTarget();
-                const int_info = if (ty.isAbiInt()) ty.intInfo(target) else std.builtin.Type.Int{
-                    .signedness = .unsigned,
-                    .bits = @intCast(u16, ty.bitSize(target)),
-                };
+            .none => if (!is_big) return,
+            .bits => {},
+        }
 
-                const cty = try dg.typeToCType(ty, .complete);
-                if (cty.tag() == .array) try writer.print(", {}", .{int_info.signedness == .signed});
+        const target = dg.module.getTarget();
+        const int_info = if (ty.isAbiInt()) ty.intInfo(target) else std.builtin.Type.Int{
+            .signedness = .unsigned,
+            .bits = @intCast(u16, ty.bitSize(target)),
+        };
 
-                var bits_pl = Value.Payload.U64{ .base = .{ .tag = .int_u64 }, .data = int_info.bits };
-                try writer.print(", {}", .{try dg.fmtIntLiteral(switch (cty.tag()) {
-                    else => Type.u8,
-                    .array => Type.u16,
-                }, Value.initPayload(&bits_pl.base), .FunctionArgument)});
-            },
-        }
+        if (is_big) try writer.print(", {}", .{int_info.signedness == .signed});
+
+        var bits_pl = Value.Payload.U64{ .base = .{ .tag = .int_u64 }, .data = int_info.bits };
+        try writer.print(", {}", .{try dg.fmtIntLiteral(
+            if (is_big) Type.u16 else Type.u8,
+            Value.initPayload(&bits_pl.base),
+            .FunctionArgument,
+        )});
     }
 
     fn fmtIntLiteral(
@@ -6099,20 +6102,24 @@ fn airBinBuiltinCall(
         return .none;
     }
 
+    const operand_ty = f.air.typeOf(bin_op.lhs);
+    const operand_cty = try f.typeToCType(operand_ty, .complete);
+    const is_big = operand_cty.tag() == .array;
+
     const lhs = try f.resolveInst(bin_op.lhs);
     const rhs = try f.resolveInst(bin_op.rhs);
-    try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
+    if (!is_big) try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
 
     const inst_ty = f.air.typeOfIndex(inst);
     const inst_scalar_ty = inst_ty.scalarType();
-    const operand_ty = f.air.typeOf(bin_op.lhs);
     const scalar_ty = operand_ty.scalarType();
 
     const inst_scalar_cty = try f.typeToCType(inst_scalar_ty, .complete);
     const ref_ret = inst_scalar_cty.tag() == .array;
 
     const writer = f.object.writer();
     const local = try f.allocLocal(inst, inst_ty);
+    if (is_big) try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
     const v = try Vectorizer.start(f, inst, writer, operand_ty);
     if (!ref_ret) {
         try f.writeCValue(writer, local, .Other);

test/behavior/int_div.zig

@@ -91,3 +91,22 @@ fn mod(comptime T: type, a: T, b: T) T {
 fn rem(comptime T: type, a: T, b: T) T {
     return @rem(a, b);
 }
+
+test "large integer division" {
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
+
+    {
+        var numerator: u256 = 99999999999999999997315645440;
+        var divisor: u256 = 10000000000000000000000000000;
+        try expect(numerator / divisor == 9);
+    }
+    {
+        var numerator: u256 = 99999999999999999999000000000000000000000;
+        var divisor: u256 = 10000000000000000000000000000000000000000;
+        try expect(numerator / divisor == 9);
+    }
+}