From 99f6d89dfbcd7ef947b30958711221075cd6dc7e Mon Sep 17 00:00:00 2001
From: chenyu <chenyu@fastmail.com>
Date: Thu, 8 May 2025 22:38:56 -0400
Subject: [PATCH] tighter idiv bound for symbolic denominator (#10226)

---
 test/unit/test_uop_vmin_vmax.py | 21 +++++++++++++++++++++
 tinygrad/ops.py                 |  7 ++++---
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/test/unit/test_uop_vmin_vmax.py b/test/unit/test_uop_vmin_vmax.py
index 59ce0e9a93..e0467e3b7f 100644
--- a/test/unit/test_uop_vmin_vmax.py
+++ b/test/unit/test_uop_vmin_vmax.py
@@ -147,6 +147,27 @@ class TestVminVmaxDivMod(unittest.TestCase):
     self.assertEqual(uop.vmin, -3)
     self.assertEqual(uop.vmax, 3)
 
+  def test_vmin_vmax_div_symbolic(self):
+    x = UOp.variable('x', 1, 10)
+    y = UOp.variable('y', 3, 5)
+    self.assertEqual((x//y).vmin, 0)
+    self.assertEqual((x//y).vmax, 3)
+    self.assertEqual(((-x)//y).vmin, -3)
+    self.assertEqual(((-x)//y).vmax, 0)
+    self.assertEqual((x//(-y)).vmin, -3)
+    self.assertEqual((x//(-y)).vmax, 0)
+    self.assertEqual(((-x)//(-y)).vmin, 0)
+    self.assertEqual(((-x)//(-y)).vmax, 3)
+
+    self.assertEqual((100//y).vmin, 20)
+    self.assertEqual((100//y).vmax, 33)
+    self.assertEqual(((-100)//y).vmin, -33)
+    self.assertEqual(((-100)//y).vmax, -20)
+    self.assertEqual((100//(-y)).vmin, -33)
+    self.assertEqual((100//(-y)).vmax, -20)
+    self.assertEqual(((-100)//(-y)).vmin, 20)
+    self.assertEqual(((-100)//(-y)).vmax, 33)
+
   def test_vmin_vmax_mod_positive(self):
     # vmin and vmax for modulo of a variable by a positive constant
     x = UOp.variable('x', 10, 20)
diff --git a/tinygrad/ops.py b/tinygrad/ops.py
index 2ee80b53b2..d693567f7e 100644
--- a/tinygrad/ops.py
+++ b/tinygrad/ops.py
@@ -634,9 +634,10 @@ class UOp(MathTrait, metaclass=UOpMetaClass):
         if (c:=s1_vmin) == s1_vmax:  # s1 is a const
           if c > 0: return cdiv(s0_vmin, c), cdiv(s0_vmax, c)
           if c < 0: return cdiv(s0_vmax, c), cdiv(s0_vmin, c)
-        # don't know exact bounds, but know the sign
-        if (s0_vmax <= 0 and s1_vmax < 0) or (s0_vmin >= 0 and s1_vmin > 0): return 0, dtypes.max(self.dtype)
-        if (s0_vmax <= 0 and s1_vmin > 0) or (s0_vmin >= 0 and s1_vmax < 0): return dtypes.min(self.dtype), 0
+        if (s0_vmax <= 0 and s1_vmax < 0): return cdiv(s0_vmax, s1_vmin), cdiv(s0_vmin, s1_vmax)
+        if (s0_vmin >= 0 and s1_vmin > 0): return cdiv(s0_vmin, s1_vmax), cdiv(s0_vmax, s1_vmin)
+        if (s0_vmax <= 0 and s1_vmin > 0): return cdiv(s0_vmin, s1_vmin), cdiv(s0_vmax, s1_vmax)
+        if (s0_vmin >= 0 and s1_vmax < 0): return cdiv(s0_vmax, s1_vmax), cdiv(s0_vmin, s1_vmin)
       if self.op is Ops.MAX: return max(s0_vmin, s1_vmin), max(s0_vmax, s1_vmax)
       if self.op is Ops.CMPLT: return (s0_vmax<s1_vmin, s0_vmin<s1_vmax)
       if self.op is Ops.CMPNE: return ((s0_vmax < s1_vmin) or (s1_vmax < s0_vmin), not (s0_vmin == s0_vmax == s1_vmin == s1_vmax))