NVFP4-1.1: Use nvvm.inline_ptx instead of llvm.inline_asm for f32→i32

llvm.inline_asm fails with 'LLVM ERROR: unsupported operation' in CuTeDSL
lowering pipeline. Switch to nvvm.inline_ptx which is native to the NVVM
dialect and lowers correctly.

- f32_to_i32_rni: cvt.rni.s32.f32 via nvvm.inline_ptx
- f32_to_i32_rz: cvt.rzi.s32.f32 via nvvm.inline_ptx
- f32_to_i32_rmi: cvt.rmi.s32.f32 via nvvm.inline_ptx

dsv4/kernels/gemm/fp4_quant.py

@@ -13,26 +13,34 @@ FP8 E4M3 format (VERIFIED against PyTorch — bias is 7, NOT 8):
 - Min positive subnormal: 2^(-9) ≈ 0.001953
 
 CuTeDSL constraints:
-- float-to-int via inline PTX cvt.rni.s32.f32 (proper hardware rounding)
+- float-to-int via NVVM inline PTX cvt.rni.s32.f32 (proper hardware rounding)
+  Using nvvm.inline_ptx which lowers correctly through the NVVM pipeline.
+  The llvm.inline_asm approach FAILS with "unsupported operation" in the
+  CuTeDSL lowering pipeline — use nvvm dialect directly.
 - `cute.arch.fmax`/`cute.arch.fmin` for float min/max (NOT cute.math.fmin/fmax)
 - `@cute.jit` decorator required for CuTeDSL functions with dynamic `if` blocks
 - `cutlass.Int32(N)` creates Int32 constants; `cutlass.Float32(N)` creates Float32 constants
-- `@dsl_user_op` + `llvm.inline_asm` for PTX instructions not exposed by CuTeDSL
+- `@dsl_user_op` for PTX instruction wrappers
 """
 
 import cutlass
 import cutlass.cute as cute
 from cutlass.cutlass_dsl import dsl_user_op, T
-from cutlass._mlir.dialects import llvm
+from cutlass._mlir.dialects import nvvm
 from cutlass.cute.typing import Float32, Int32
 
 FP8_E4M3_BIAS = 7
 
 
-# ── Inline PTX float-to-int conversion ──────────────────────────────
+# ── NVVM inline PTX float-to-int conversion ─────────────────────────
 # CuTeDSL has no built-in f32→i32 conversion. We wrap PTX cvt instructions
-# via @dsl_user_op + llvm.inline_asm. This is the PROPER approach — hardware
+# via @dsl_user_op + nvvm.inline_ptx. This is the PROPER approach — hardware
 # rounding, no threshold hacks, no approximation.
+#
+# IMPORTANT: We use nvvm.inline_ptx (NVVM dialect), NOT llvm.inline_asm.
+# llvm.inline_asm fails with "LLVM ERROR: unsupported operation" because the
+# CuTeDSL lowering pipeline cannot lower it to NVVM. The nvvm.inline_ptx op
+# is native to the NVVM dialect and lowers correctly.
 
 @dsl_user_op
 def f32_to_i32_rni(x: Float32, *, loc=None, ip=None) -> Int32:
@@ -41,19 +49,14 @@ def f32_to_i32_rni(x: Float32, *, loc=None, ip=None) -> Int32:
     Wraps PTX: cvt.rni.s32.f32 $0, $1;
     Equivalent to CUDA __float2int_rn().
     """
-    return Int32(
-        llvm.inline_asm(
-            T.i32(),
-            [Float32(x).ir_value(loc=loc, ip=ip)],
-            "cvt.rni.s32.f32 $0, $1;",
-            "=r,f",
-            has_side_effects=False,
-            is_align_stack=False,
-            asm_dialect=llvm.AsmDialect.AD_ATT,
-            loc=loc,
-            ip=ip,
-        )
+    result = nvvm.inline_ptx(
+        write_only_args=[T.i32()],
+        read_only_args=[Float32(x).ir_value(loc=loc, ip=ip)],
+        ptx_code="cvt.rni.s32.f32 $0, $1;",
+        loc=loc,
+        ip=ip,
     )
+    return Int32(result)
 
 
 @dsl_user_op
@@ -61,21 +64,16 @@ def f32_to_i32_rz(x: Float32, *, loc=None, ip=None) -> Int32:
     """Convert Float32 to Int32 with round-toward-zero (RZ).
     
     Wraps PTX: cvt.rzi.s32.f32 $0, $1;
-    Equivalent to CUDA __float2int_rz(). Used for floor-based extraction.
+    Equivalent to CUDA __float2int_rz(). Used for truncation.
     """
-    return Int32(
-        llvm.inline_asm(
-            T.i32(),
-            [Float32(x).ir_value(loc=loc, ip=ip)],
-            "cvt.rzi.s32.f32 $0, $1;",
-            "=r,f",
-            has_side_effects=False,
-            is_align_stack=False,
-            asm_dialect=llvm.AsmDialect.AD_ATT,
-            loc=loc,
-            ip=ip,
-        )
+    result = nvvm.inline_ptx(
+        write_only_args=[T.i32()],
+        read_only_args=[Float32(x).ir_value(loc=loc, ip=ip)],
+        ptx_code="cvt.rzi.s32.f32 $0, $1;",
+        loc=loc,
+        ip=ip,
     )
+    return Int32(result)
 
 
 @dsl_user_op
@@ -86,19 +84,14 @@ def f32_to_i32_rmi(x: Float32, *, loc=None, ip=None) -> Int32:
     Equivalent to CUDA __float2int_rd() / floorf() → int.
     Used for floor(log2()) extraction in FP8 encoding.
     """
-    return Int32(
-        llvm.inline_asm(
-            T.i32(),
-            [Float32(x).ir_value(loc=loc, ip=ip)],
-            "cvt.rmi.s32.f32 $0, $1;",
-            "=r,f",
-            has_side_effects=False,
-            is_align_stack=False,
-            asm_dialect=llvm.AsmDialect.AD_ATT,
-            loc=loc,
-            ip=ip,
-        )
+    result = nvvm.inline_ptx(
+        write_only_args=[T.i32()],
+        read_only_args=[Float32(x).ir_value(loc=loc, ip=ip)],
+        ptx_code="cvt.rmi.s32.f32 $0, $1;",
+        loc=loc,
+        ip=ip,
     )
+    return Int32(result)
 
 
 # ── FP8 E4M3 encoding ───────────────────────────────────────────────
@@ -281,13 +274,8 @@ def quantize_e2m1_nibble(
         
         # LUT: half_step → E2M1 index
         # [0,1,2,3,4,4,5,6,6,6,7,7]
+        # Expressed as branch logic (CuTeDSL has no random-access arrays in @cute.jit)
         idx = cutlass.Int32(0)
-        # We can't index an array in CuTeDSL, so implement the LUT with comparisons.
-        # This IS the LUT, just expressed as branch logic since CuTeDSL has no
-        # random-access shared arrays in @cute.jit scalar functions.
-        #
-        # The LUT is: half_step_to_e2m1[hs] for hs in 0..11
-        #   0→0, 1→1, 2→2, 3→3, 4→4, 5→4, 6→5, 7→6, 8→6, 9→6, 10→7, 11→7
         if half_step >= cutlass.Int32(1):
             idx = cutlass.Int32(1)
         if half_step >= cutlass.Int32(2):