Validate native Windows M against real PTX and correct patch-merge bounds

kernels/m/swin_block.h

@@ -718,7 +718,16 @@ __device__ __forceinline__ void swin_block(const CommonParams& p, const TubePara
                 if (MX < 0 || MX >= W2 || MY < 0 || MY >= H2)
                     continue;
                 p.p48[((size_t)((ch >> 5) * H2 + MY) * W2 + MX) * 32 + (ch & 31)] =
-                    (uint8_t)enc8(y[j].get(i));
+                    (uint8_t)enc8(
+#ifdef SWIN_EXACT
+                        // The audited 310.9 patch-merge path bounds the f16
+                        // result to +/- 2*pi before e4m3 quantisation.
+                        __builtin_elementwise_max(__builtin_elementwise_min(y[j].get(i), (half_t)6.283185307179586f),
+                                                  (half_t)-6.283185307179586f)
+#else
+                        y[j].get(i)
+#endif
+                    );
             }
         }
     }

kernels/tools/ptxsim.py

@@ -96,7 +96,8 @@ def split_args(s):
 
 
 def parse_kernel(path, name):
-    src = open(path).read()
+    with open(path) as file:
+        src = file.read()
     i = src.index('.entry ' + name + '(')
     j = src.find('\n.visible', i + 10)
     j = len(src) if j < 0 else j
@@ -340,12 +341,11 @@ class Block:
         steps = 0
         while pc < len(stmts):
             st = stmts[pc]
-            for l in st.labels:
-                if l in pending:
-                    active |= pending.pop(l)
+            if pc in pending:
+                active |= pending.pop(pc)
             if not active.any():
-                # jump to the nearest label someone waits at
-                targets = sorted(self.labels[l] for l in pending)
+                # Reconverge at either a forward target or a loop fallthrough.
+                targets = sorted(pending)
                 if not targets:
                     break
                 pc = targets[0]
@@ -365,10 +365,16 @@ class Block:
                     if not taking.any():
                         pc += 1
                         continue
-                    raise NotImplementedError('divergent backward branch at ' + st.text)
+                    # Lanes finishing a loop wait at its fallthrough while the
+                    # other lanes execute their remaining iterations. Their
+                    # registers and memory writes stay masked until reconvergence.
+                    pending[pc + 1] = pending.get(pc + 1, np.zeros(self.T, bool)) | (active & ~taking)
+                    active = taking.copy()
+                    pc = target
+                    continue
                 active = active & ~taking
                 if taking.any():
-                    pending[st.args[0]] = pending.get(st.args[0], np.zeros(self.T, bool)) | taking
+                    pending[target] = pending.get(target, np.zeros(self.T, bool)) | taking
                 pc += 1
                 continue
             if mask.any() or st.op.startswith(('mma', 'shfl', 'movmatrix', 'bar')):

kernels/tools/swin_check.py

@@ -23,6 +23,10 @@ import swin_model as sm  # noqa: E402
 LAYERS = {'enc1': (64, 2, 96, 0), 'enc2': (96, 4, 128, 0), 'enc3_tube': (128, 4, 0, 0), 'dec2': (96, 4, 0, 128),
           'dec1': (64, 2, 0, 96)}
 
+# Preserve the existing Linux oracle by default; Windows strict replay enables
+# the audited 310.9 f16 patch-merge bound before final e4m3 quantisation.
+CLAMP_PATCH_MERGE = False
+
 
 def blocks(grid, n, seed=1):
     gx, gy = grid[0], grid[1]
@@ -47,7 +51,11 @@ def model_block(P, layer, bx, by):
             Wg = me.E4M3[P.wbuf[sm.woff_table(PM0 + g * 128 * C, 512, 64 * C, 4 * C, 32)]]
             bias = P.f16vec(PM0 + 4 * C * NPM + 64 * g, 32)
             cols.append(me.mma_chain(A, Wg, C0=np.broadcast_to(bias, (16, 32)).copy()))
-        merged = me.q8(sm.pair_to_nat(np.concatenate(cols, axis=1)))
+        merged = sm.pair_to_nat(np.concatenate(cols, axis=1))
+        if CLAMP_PATCH_MERGE:
+            limit = me.f16(2 * np.pi)
+            merged = np.clip(merged, -limit, limit)
+        merged = me.q8(merged)
     return out, merged