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Diffstat (limited to 'docs/NVPTXUsage.rst')
| -rw-r--r-- | docs/NVPTXUsage.rst | 46 |
1 files changed, 19 insertions, 27 deletions
diff --git a/docs/NVPTXUsage.rst b/docs/NVPTXUsage.rst index fdfc8e41dc3b..159fe078653c 100644 --- a/docs/NVPTXUsage.rst +++ b/docs/NVPTXUsage.rst @@ -289,7 +289,7 @@ code often follows a pattern: return my_function_precise(a); } -The default value for all unspecified reflection parameters is zero. +The default value for all unspecified reflection parameters is zero. The ``NVVMReflect`` pass should be executed early in the optimization pipeline, immediately after the link stage. The ``internalize`` pass is also @@ -326,6 +326,16 @@ often leave behind dead code of the form: Therefore, it is recommended that ``NVVMReflect`` is executed early in the optimization pipeline before dead-code elimination. +The NVPTX TargetMachine knows how to schedule ``NVVMReflect`` at the beginning +of your pass manager; just use the following code when setting up your pass +manager: + +.. code-block:: c++ + + std::unique_ptr<TargetMachine> TM = ...; + PassManagerBuilder PMBuilder(...); + if (TM) + TM->adjustPassManager(PMBuilder); Reflection Parameters --------------------- @@ -339,35 +349,17 @@ Flag Description ``__CUDA_FTZ=[0,1]`` Use optimized code paths that flush subnormals to zero ==================== ====================================================== +The value of this flag is determined by the "nvvm-reflect-ftz" module flag. +The following sets the ftz flag to 1. -Invoking NVVMReflect --------------------- - -To ensure that all dead code caused by the reflection pass is eliminated, it -is recommended that the reflection pass is executed early in the LLVM IR -optimization pipeline. The pass takes an optional mapping of reflection -parameter name to an integer value. This mapping can be specified as either a -command-line option to ``opt`` or as an LLVM ``StringMap<int>`` object when -programmatically creating a pass pipeline. - -With ``opt``: - -.. code-block:: text - - # opt -nvvm-reflect -nvvm-reflect-list=<var>=<value>,<var>=<value> module.bc -o module.reflect.bc - - -With programmatic pass pipeline: - -.. code-block:: c++ - - extern FunctionPass *llvm::createNVVMReflectPass(const StringMap<int>& Mapping); - - StringMap<int> ReflectParams; - ReflectParams["__CUDA_FTZ"] = 1; - Passes.add(createNVVMReflectPass(ReflectParams)); +.. code-block:: llvm + !llvm.module.flag = !{!0} + !0 = !{i32 4, !"nvvm-reflect-ftz", i32 1} +(``i32 4`` indicates that the value set here overrides the value in another +module we link with. See the `LangRef <LangRef.html#module-flags-metadata>` +for details.) Executing PTX ============= |