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[cffLib.specializer] Make command-merging linear again

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The consideration for blends had made it into O(n^2).
Make it linear again.

Speeds up Tests/cffLib/specializer_test.py::CFFSpecializeProgramTest::test_maxstack_blends
3x for me.
This commit is contained in:
Behdad Esfahbod 2024-11-12 18:43:03 -07:00
parent 7e6d31569f
commit cfba1f995f
2 changed files with 9 additions and 13 deletions
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18
Lib/fontTools/cffLib/specializer.py
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@ -715,6 +715,7 @@ def specializeCommands(
continue continue
# 5. Combine adjacent operators when possible, minding not to go over max stack size. # 5. Combine adjacent operators when possible, minding not to go over max stack size.
stackUse = _argsStackUse(commands[-1][1]) if commands else 0
for i in range(len(commands) - 1, 0, -1): for i in range(len(commands) - 1, 0, -1):
op1, args1 = commands[i - 1] op1, args1 = commands[i - 1]
op2, args2 = commands[i] op2, args2 = commands[i]
@ -764,19 +765,14 @@ def specializeCommands(
# Make sure the stack depth does not exceed (maxstack - 1), so # Make sure the stack depth does not exceed (maxstack - 1), so
# that subroutinizer can insert subroutine calls at any point. # that subroutinizer can insert subroutine calls at any point.
# args1StackUse = _argsStackUse(args1)
# The assumption is that args1, and args2, each individually combinedStackUse = max(args1StackUse, len(args1) + stackUse)
# can be successfully processed without a stack overflow. if new_op and combinedStackUse < maxstack:
# When combined, the stack depth to consider would be the
# number of items in args1 plus what it takes to build args2
# on top of args1, which will be already on the stack as
# len(args1) items.
#
# It's unfortunate that _argsStackUse() is O(n) in the number
# of args, but it's not a big deal hopefully.
if new_op and len(args1) + _argsStackUse(args2) < maxstack:
commands[i - 1] = (new_op, args1 + args2) commands[i - 1] = (new_op, args1 + args2)
del commands[i] del commands[i]
stackUse = combinedStackUse
else:
stackUse = args1StackUse
# 6. Resolve any remaining made-up operators into real operators. # 6. Resolve any remaining made-up operators into real operators.
for i in range(len(commands)): for i in range(len(commands)):

4
Tests/cffLib/specializer_test.py
View File

@ -599,8 +599,8 @@ class CFFSpecializeProgramTest:
stack_use = charstr_stack_use(specialized, getNumRegions=getNumRegions) stack_use = charstr_stack_use(specialized, getNumRegions=getNumRegions)
assert maxStack - numRegions < stack_use < maxStack assert maxStack - numRegions < stack_use < maxStack
def test_maxstack_blends2(self): def test_maxstack_commands(self):
# See if two long blend sequences are merged into one # See if two commands with deep blends are merged into one
numRegions = 400 numRegions = 400
numOps = 2 numOps = 2
getNumRegions = lambda iv: numRegions getNumRegions = lambda iv: numRegions