[SingleSource] Add variants with forced opts for vectorizer tests. (#368)

Add a few variants with different forced options:
 * tail-folding forced with different modes
 * instruction costs forced

This should increase the test coverage for different option combinations
on more platforms (e.g. testing tail-folding even on targets where it is
not the default).

Hopefully makes it a bit easier to discover miscompiles, e.g. like
llvm/llvm-project#182492.

PR: #368

Author: fhahn

SingleSource/UnitTests/Vectorizer/CMakeLists.txt

@@ -1,8 +1,51 @@
+set(CMAKE_CXX_STANDARD 17)
 llvm_singlesource()
-set_property(TARGET runtime-checks PROPERTY CXX_STANDARD 17)
-set_property(TARGET early-exit PROPERTY CXX_STANDARD 17)
 
 # The VPlan-native path is specific to llvm.
 if ("${CMAKE_C_COMPILER_ID}" MATCHES "Clang")
   add_subdirectory(VPlanNativePath)
+
+  set(BASE_CXXFLAGS ${CXXFLAGS})
+
+  # Add targets for all tests with forced tail folding.
+  list(APPEND CXXFLAGS
+    "-mllvm" "-prefer-predicate-over-epilogue=predicate-dont-vectorize"
+    "-mllvm" "-force-tail-folding-style=data"
+  )
+  llvm_singlesource(PREFIX "tfactivelanemask-")
+
+  # Add targets for all tests with forced tail folding using data without lane mask.
+  set(CXXFLAGS ${BASE_CXXFLAGS})
+  list(APPEND CXXFLAGS
+    "-mllvm" "-prefer-predicate-over-epilogue=predicate-dont-vectorize"
+    "-mllvm" "-force-tail-folding-style=data-without-lane-mask"
+  )
+  llvm_singlesource(PREFIX "tf-")
+
+  # Add targets with instruction cost forced to 1.
+  set(CXXFLAGS ${BASE_CXXFLAGS})
+  list(APPEND CXXFLAGS
+    "-mllvm" "-force-target-instruction-cost=1"
+  )
+  llvm_singlesource(PREFIX "ftic-")
+
+  # Add targets with instruction cost forced to 1 and forced tail-folding.
+  set(CXXFLAGS ${BASE_CXXFLAGS})
+  list(APPEND CXXFLAGS
+    "-mllvm" "-force-target-instruction-cost=1"
+    "-mllvm" "-prefer-predicate-over-epilogue=predicate-dont-vectorize"
+    "-mllvm" "-force-tail-folding-style=data"
+  )
+  llvm_singlesource(PREFIX "tfactivelanemask-ftic-")
+
+  # Add targets with instruction cost forced to 1 and forced tail-folding without lane mask.
+  set(CXXFLAGS ${BASE_CXXFLAGS})
+  list(APPEND CXXFLAGS
+    "-mllvm" "-force-target-instruction-cost=1"
+    "-mllvm" "-prefer-predicate-over-epilogue=predicate-dont-vectorize"
+    "-mllvm" "-force-tail-folding-style=data-without-lane-mask"
+  )
+  llvm_singlesource(PREFIX "tf-ftic-")
+
+  set(CXXFLAGS ${BASE_CXXFLAGS})
 endif()