fix(cuda_core): use nvJitLink-compatible 0/1 values for boolean linker options

cuda_core/cuda/core/_linker.pyx

@@ -400,13 +400,13 @@ class LinkerOptions:
         if self.lineinfo:
             options.append("-lineinfo")
         if self.ftz is not None:
-            options.append(f"-ftz={'true' if self.ftz else 'false'}")
+            options.append(f"-ftz={'1' if self.ftz else '0'}")
         if self.prec_div is not None:
-            options.append(f"-prec-div={'true' if self.prec_div else 'false'}")
+            options.append(f"-prec-div={'1' if self.prec_div else '0'}")
         if self.prec_sqrt is not None:
-            options.append(f"-prec-sqrt={'true' if self.prec_sqrt else 'false'}")
+            options.append(f"-prec-sqrt={'1' if self.prec_sqrt else '0'}")
         if self.fma is not None:
-            options.append(f"-fma={'true' if self.fma else 'false'}")
+            options.append(f"-fma={'1' if self.fma else '0'}")
         if self.kernels_used is not None:
             if isinstance(self.kernels_used, str):
                 options.append(f"-kernels-used={self.kernels_used}")
@@ -428,9 +428,9 @@ class LinkerOptions:
                 for opt in self.ptxas_options:
                     options.append(f"-Xptxas={opt}")
         if self.split_compile is not None:
-            options.append(f"-split-compile={self.split_compile}")
+            options.append(f"-split-compile={int(self.split_compile)}")
         if self.split_compile_extended is not None:
-            options.append(f"-split-compile-extended={self.split_compile_extended}")
+            options.append(f"-split-compile-extended={int(self.split_compile_extended)}")
         if self.no_cache is True:
             options.append("-no-cache")
 

cuda_core/tests/test_linker.py

@@ -206,10 +206,36 @@ def test_linker_options_as_bytes_nvjitlink():
     options_str = [opt.decode() for opt in nvjitlink_options]
     assert "-arch=sm_80" in options_str
     assert "-g" in options_str
-    assert "-ftz=true" in options_str
+    assert "-ftz=1" in options_str
     assert "-maxrregcount=32" in options_str
 
 
+@pytest.mark.agent_authored(model="claude-sonnet-5")
+@pytest.mark.skipif(is_culink_backend, reason="ftz/prec_div/prec_sqrt/fma are nvjitlink-only options")
+def test_linker_lto_enabled_runtime_accepts_bool_options(compile_ltoir_functions):
+    """Regression test for nvbug 6621758: actual LTO-enabled link, not just option setter.
+
+    With ``link_time_optimization=True``, ``-ftz``/``-prec-div``/``-prec-sqrt``/``-fma``
+    are forwarded to libnvvm and actually validated at link time, unlike in a non-LTO
+    link where legacy ``true``/``false`` values are silently ignored. Only ``0``/``1``
+    reliably takes effect here on any CUDA version.
+
+    The test checks that Python ``True``/``False`` values are correctly
+    mapped to ``1``/``0`` and accepted by the nvJitLink backend during an LTO-enabled link.
+    """
+    options = LinkerOptions(
+        arch=ARCH,
+        link_time_optimization=True,
+        ftz=True,
+        prec_div=True,
+        prec_sqrt=True,
+        fma=True,
+    )
+    linker = Linker(*compile_ltoir_functions, options=options)
+    linked_code = linker.link("cubin")
+    assert isinstance(linked_code, ObjectCode)
+
+
 @pytest.mark.agent_authored(model="gpt-5.6")
 @pytest.mark.skipif(is_culink_backend, reason="as_bytes() only supported for nvjitlink backend")
 @pytest.mark.parametrize("value,expected_count", [(None, 0), (False, 0), (True, 1)])