Allow conditional lit tests in Subzero, based on build flags.

tests_lit/lit.cfg

Index: tests_lit/lit.cfg
diff --git a/tests_lit/lit.cfg b/tests_lit/lit.cfg
index 825f7d2b3051d4bc366080b71cdbb696fc540b91..1233a76d4fbf7e8d0ebbe2b2af7096320e0c0819 100644
--- a/tests_lit/lit.cfg
+++ b/tests_lit/lit.cfg
@@ -1,7 +1,36 @@
+# -*- Python -*-
 # Taken from utils/lit/tests in the LLVM tree and hacked together to support
 # our tests.
-
-# -*- Python -*-
+#
+# Note: This configuration has simple commands to run Subzero's translator.
+# They have the form %X2i (i.e. %p2i, %l2i, and %lc2i) where X is defined
+# as follows:
+#
+#   p : Run Subzero's translator, building ICE from PNaCl bitcode directly.
+#   l : Run Subzero's translator, converting the .ll file to a PNaCl bitcode
+#       file, reading in the bitcode file and generating LLVM IR, and
+#       then convert LLVM IR to ICE IR.
+#   lc : Run Subzero's translator, directly parsing the .ll file into LLVM IR,
+#        and then convert it to ICE IR.
+#
+# These commands can be used in RUN lines by FileCheck. If the Subzero
+# build being tested lacks any required attributes (e.g., the ability
+# to parse .ll files), the command will simply return successfully,
+# generating no output. This allows translation tests to be able to
+# conditionally test the translator, based on the translator built.
+#
+# This conditional handling of translation introduces potential problems
+# when the output is piped to another command on a RUN line. Executables
+# like FileCheck expect non-empty input.
+#
+# To handle the problem that the pipe is conditional, any command that
+# doesn't accept empty input should be prefixed by a corresponding
+# %ifX (i.e. %p2i, %ifl, or %ifpc). Note: %p2i should always work, and
+# hence %ifp is not necessary (i.e. it is a nop).
+#
+# If you need to check other build attributes (other than the
+# existence of %l2i and %lc2i), you can use the %if command (which is
+# a short hand for using pydir/ifatts.py).
 
 import os
 import re
@@ -11,6 +40,7 @@ import lit.formats
 
 sys.path.insert(0, 'pydir')
 from utils import FindBaseNaCl
+from ifatts import GetFileAttributes
 
 # name: The name of this test suite.
 config.name = 'subzero'
@@ -37,34 +67,39 @@ pydir = os.path.join(bin_root, 'pydir')
 # the llvmbintools list.
 llvmbinpath = os.path.abspath(os.environ.get('LLVM_BIN_PATH'))
 
-# Finding Subzero tools
+# Define the location of the llvm2ice tool.
 llvm2icetool = os.path.join(bin_root, 'llvm2ice')
-
-# Convert LLVM source to PNaCl bitcode, read using the
-# Subzero bitcode reader, and then translate.
-config.substitutions.append(
-  ('%p2i', ' '.join([os.path.join(pydir, 'run-llvm2ice.py'),
-                     '--llvm2ice', llvm2icetool,
-                     '--llvm-bin-path', llvmbinpath
-                    ])))
-
-# Convert LLVM source to PNaCl bitcode, read using the PNaCl bitcode reader,
-# convert to ICE using the ICE Converter, and then translate.
-# TODO(kschimpf) Deprecated, remove once p2i working.
-config.substitutions.append(
-  ('%l2i', ' '.join([os.path.join(pydir, 'run-llvm2ice.py'),
-                     '--llvm', '--llvm2ice', llvm2icetool,
-                     '--llvm-bin-path', llvmbinpath
-                    ])))
-
-# Read LLVM source, convert to ICE using the ICE converter, and then translate.
-# Note: l2i is preferred over lc2i, since it uses PNaCl bitcode.
-# TODO(kschimpf) Deprecated, remove once p2i working.
-config.substitutions.append(
-  ('%lc2i', ' '.join([os.path.join(pydir, 'run-llvm2ice.py'),
-                      '--llvm-source', '--llvm2ice', llvm2icetool,
-                      '--llvm-bin-path', llvmbinpath
-                    ])))
+llvm2icetoolatts = os.path.join(bin_root, 'llvm2ice.build_atts')
+
+# Add build attributes of llvm2ice tool to the set of available features.
+config.available_features.update(GetFileAttributes(llvm2icetoolatts))
+
+# Base command for testing build attributes
+if_atts_base = [os.path.join(pydir, 'ifatts.py'), llvm2icetoolatts]
+if_atts_cmd = if_atts_base + ['--command']
+ifl2i_atts_cmd = if_atts_base + ['--att=allow_llvm_ir', '--command']
+iflc2i_atts_cmd = if_atts_base + ['--att=allow_llvm_ir',
+                                  '--att=allow_llvm_ir_as_input',
+                                  '--command']
+
+# Base command for running llvm2ice
+llvm2ice_cmd = [os.path.join(pydir, 'run-llvm2ice.py'),
+                '--llvm2ice', llvm2icetool,
+                '--llvm-bin-path', llvmbinpath]
+
+# Run commands only if corresponding build attributes apply, including
+# for each compiler setup.
+config.substitutions.append(('%ifp', ' '))
+config.substitutions.append(('%iflc', ' '.join(iflc2i_atts_cmd)))
+config.substitutions.append(('%ifl', ' '.join(ifl2i_atts_cmd)))
+config.substitutions.append(('%if', ' '.join(if_atts_cmd)))
+
+# Translate LLVM source for each compiler setup.
+config.substitutions.append(('%p2i', ' '.join(llvm2ice_cmd)))
+config.substitutions.append(('%l2i', ' '.join(ifl2i_atts_cmd + llvm2ice_cmd
+                                              + ['--llvm'])))
+config.substitutions.append(('%lc2i', ' '.join(iflc2i_atts_cmd + llvm2ice_cmd
+                                               + ['--llvm-source'])))
 
 config.substitutions.append(('%llvm2ice', llvm2icetool))
 config.substitutions.append(('%szdiff', os.path.join(pydir, 'szdiff.py')))