[shuffle] Teach the shuffle fuzzer to fuzz blends, including forming

a tree of inputs to blend iteratively together.

This required a pretty substantial rewrite of the innards. The number of
shuffle instructions is now bounded in terms of tree-height. There is
a flag to disable blends so that its still possible to test single input
shuffles. I've also improved various aspects of how the test program is
generated, primarily to simplify the test harness and allow some
optimizations to clean up how we actually check the results and build up
the inputs.

Again, apologies for my likely horrible use of Python... But hey, it
works! (Ish?)

llvm-svn: 215530

utils/shuffle_fuzz.py

@@ -24,8 +24,10 @@ def main():
                       help='A string used to seed the RNG')
   parser.add_argument('-v', '--verbose', action='store_true',
                       help='Show verbose output')
-  parser.add_argument('--fixed-num-shuffles', type=int,
-                      help='Specify a fixed number of shuffles to test')
+  parser.add_argument('--max-shuffle-height', type=int, default=16,
+                      help='Specify a fixed height of shuffle tree to test')
+  parser.add_argument('--no-blends', dest='blends', action='store_false',
+                      help='Include blends of two input vectors')
   parser.add_argument('--fixed-bit-width', type=int, choices=[128, 256],
                       help='Specify a fixed bit width of vector to test')
   parser.add_argument('--triple',
@@ -49,33 +51,46 @@ def main():
     width = random.choice([2, 4, 8, 16, 32, 64])
     element_type = random.choice(['i8', 'i16', 'i32', 'i64', 'f32', 'f64'])
 
-  # FIXME: Support blends.
-  shuffle_indices = [-1] + range(width)
+  element_modulus = {
+      'i8': 1 << 8, 'i16': 1 << 16, 'i32': 1 << 32, 'i64': 1 << 64,
+      'f32': 1 << 32, 'f64': 1 << 64}[element_type]
 
-  if args.fixed_num_shuffles is not None:
-    num_shuffles = args.fixed_num_shuffles
-  else:
-    num_shuffles = random.randint(0, 16)
+  shuffle_range = (2 * width) if args.blends else width
+  shuffle_indices = [-1] + range(shuffle_range)
 
-  shuffles = [[random.choice(shuffle_indices)
-               for _ in itertools.repeat(None, width)]
-              for _ in itertools.repeat(None, num_shuffles)]
+  shuffle_tree = [[[random.choice(shuffle_indices)
+                    for _ in itertools.repeat(None, width)]
+                   for _ in itertools.repeat(None, args.max_shuffle_height - i)]
+                  for i in xrange(args.max_shuffle_height)]
 
   if args.verbose:
     # Print out the shuffle sequence in a compact form.
-    print >>sys.stderr, 'Testing shuffle sequence "%s":' % (args.seed,)
-    for s in shuffles:
-      print >>sys.stderr, '  v%d%s: %s' % (width, element_type, s)
+    print >>sys.stderr, ('Testing shuffle sequence "%s" (v%d%s):' %
+                         (args.seed, width, element_type))
+    for i, shuffles in enumerate(shuffle_tree):
+      print >>sys.stderr, '  tree level %d:' % (i,)
+      for j, s in enumerate(shuffles):
+        print >>sys.stderr, '    shuffle %d: %s' % (j, s)
     print >>sys.stderr, ''
 
-  # Compute a round-trip of the shuffle.
-  result = range(1, width + 1)
-  for s in shuffles:
-    result = [result[i] if i != -1 else -1 for i in s]
+  # Symbolically evaluate the shuffle tree.
+  inputs = [[int(j % element_modulus)
+             for j in xrange(i * width + 1, (i + 1) * width + 1)]
+            for i in xrange(args.max_shuffle_height + 1)]
+  results = inputs
+  for shuffles in shuffle_tree:
+    results = [[((results[i] if j < width else results[i + 1])[j % width]
+                 if j != -1 else -1)
+                for j in s]
+               for i, s in enumerate(shuffles)]
+  if len(results) != 1:
+    print >>sys.stderr, 'ERROR: Bad results: %s' % (results,)
+    sys.exit(1)
+  result = results[0]
 
   if args.verbose:
     print >>sys.stderr, 'Which transforms:'
-    print >>sys.stderr, '  from: %s' % (range(1, width + 1),)
+    print >>sys.stderr, '  from: %s' % (inputs,)
     print >>sys.stderr, '  into: %s' % (result,)
     print >>sys.stderr, ''
 
@@ -92,22 +107,24 @@ def main():
   # Now we need to generate IR for the shuffle function.
   subst = {'N': width, 'T': element_type, 'IT': integral_element_type}
   print """
-define internal <%(N)d x %(T)s> @test(<%(N)d x %(T)s> %%v) noinline nounwind {
-entry:""" % subst
+define internal fastcc <%(N)d x %(T)s> @test(%(arguments)s) noinline nounwind {
+entry:""" % dict(subst,
+                 arguments=', '.join(
+                     ['<%(N)d x %(T)s> %%s.0.%(i)d' % dict(subst, i=i)
+                      for i in xrange(args.max_shuffle_height + 1)]))
 
-  for i, s in enumerate(shuffles):
+  for i, shuffles in enumerate(shuffle_tree):
+   for j, s in enumerate(shuffles):
     print """
-  %%s%(i)d = shufflevector <%(N)d x %(T)s> %(I)s, <%(N)d x %(T)s> undef, <%(N)d x i32> <%(S)s>
-""".strip() % dict(subst,
-                i=i,
-                I=('%%s%d' % (i - 1)) if i != 0 else '%v',
-                S=', '.join(['i32 %s' % (str(si) if si != -1 else 'undef',)
-                             for si in s]))
+  %%s.%(next_i)d.%(j)d = shufflevector <%(N)d x %(T)s> %%s.%(i)d.%(j)d, <%(N)d x %(T)s> %%s.%(i)d.%(next_j)d, <%(N)d x i32> <%(S)s>
+""".strip('\n') % dict(subst, i=i, next_i=i + 1, j=j, next_j=j + 1,
+                       S=', '.join(['i32 ' + (str(si) if si != -1 else 'undef')
+                                    for si in s]))
 
   print """
-  ret <%(N)d x %(T)s> %%s%(i)d
+  ret <%(N)d x %(T)s> %%s.%(i)d.0
 }
-""" % dict(subst, i=len(shuffles) - 1)
+""" % dict(subst, i=len(shuffle_tree))
 
   # Generate some string constants that we can use to report errors.
   for i, r in enumerate(result):
@@ -119,28 +136,39 @@ entry:""" % subst
 @error.%(i)d = private unnamed_addr global [128 x i8] c"%(s)s"
 """.strip() % {'i': i, 's': s}
 
+  # Define a wrapper function which is marked 'optnone' to prevent
+  # interprocedural optimizations from deleting the test.
+  print """
+define internal fastcc <%(N)d x %(T)s> @test_wrapper(%(arguments)s) optnone noinline {
+  %%result = call fastcc <%(N)d x %(T)s> @test(%(arguments)s)
+  ret <%(N)d x %(T)s> %%result
+}
+""" % dict(subst,
+           arguments=', '.join(['<%(N)d x %(T)s> %%s.%(i)d' % dict(subst, i=i)
+                                for i in xrange(args.max_shuffle_height + 1)]))
+
   # Finally, generate a main function which will trap if any lanes are mapped
   # incorrectly (in an observable way).
   print """
-define i32 @main() optnone noinline {
+define i32 @main() {
 entry:
   ; Create a scratch space to print error messages.
   %%str = alloca [128 x i8]
   %%str.ptr = getelementptr inbounds [128 x i8]* %%str, i32 0, i32 0
 
   ; Build the input vector and call the test function.
-  %%input = bitcast <%(N)d x %(IT)s> <%(input)s> to <%(N)d x %(T)s>
-  %%v = call <%(N)d x %(T)s> @test(<%(N)d x %(T)s> %%input)
+  %%v = call fastcc <%(N)d x %(T)s> @test_wrapper(%(inputs)s)
   ; We need to cast this back to an integer type vector to easily check the
   ; result.
   %%v.cast = bitcast <%(N)d x %(T)s> %%v to <%(N)d x %(IT)s>
   br label %%test.0
 """ % dict(subst,
-           input=', '.join(['%(IT)s %(i)s' % dict(subst, i=i)
-                            for i in xrange(1, width + 1)]),
-           result=', '.join(['%(IT)s %(i)s' % dict(subst,
-                                                   i=i if i != -1 else 'undef')
-                             for i in result]))
+           inputs=', '.join(
+               [('<%(N)d x %(T)s> bitcast '
+                 '(<%(N)d x %(IT)s> <%(input)s> to <%(N)d x %(T)s>)' %
+                 dict(subst, input=', '.join(['%(IT)s %(i)d' % dict(subst, i=i)
+                                              for i in input])))
+                for input in inputs]))
 
   # Test that each non-undef result lane contains the expected value.
   for i, r in enumerate(result):