* Refactor instruction folders
We want to refactor the instruction folder to allow different sets of
rules to be added to the instruction folder. We might want different
sets of rules in different circumstances.
We also need a way to add rules for extended instructions. Changes are
made to the FoldingRules class and ConstFoldingRules class to enable
that.
We added tests to check that we can fold extended instructions using the
new framework.
At the same time, I noticed that there were two tests that did not tests
what they were suppose to. They could not be easily salvaged. #2813 was
opened to track adding the new tests.
In C++, a bit shift of the same size as the type is undefined, but it is
defined in spir-v. When folding those cases, we have to be careful. We
cannot simply do the shift in C++.
Fixes https://crbug.com/917697.
We currently simulate all shift operations when the two operand are
constants. The problem is that if the shift amount is larger than
32, the result is undefined.
I'm changing the folder to return 0 if the shift value is too high.
That way, we will have defined behaviour.
https://crbug.com/910937.
The current implementation in the folder when seeing a division by zero
is to assert. In the release build, the compiler will attempt to
compute the value, which causes its own problems.
The solution I will go with is to fold the division, and just give it
the value of 0. The same goes for remainder and mod operations.
Fixes#1961.
This CL moves the files in opt/ to consistenly be under the opt::
namespace. This frees up the ir:: namespace so it can be used to make a
shared ir represenation.
The folding routines are currently global functions. They also rely on
data in an std::map that holds the folding rules for each opcode. This
causes that map to not have a clear owner, and therefore never gets
deleted.
There has been a request to delete this map. To implement this, we will
create a InstructionFolder class that owns the maps. The IRContext will
own the InstructionFolder instance. Then the global functions will
become public memeber functions of the InstructionFolder.
Fixes https://github.com/KhronosGroup/SPIRV-Tools/issues/1659.
There are a few locations where we need to handle duplicate types. We
cannot merge them because they may be needed for reflection. When this
happens we need do some extra lookups in the type manager.
The specific fixes are:
1) When generating a constant through `GetDefiningInstruction` accept
and use an id for the desired type of the constant. This will make sure
you get the type that is needed.
2) In Private-to-local, make sure we to update the def-use chains when a
new pointer type is created.
3) In the type manager, make sure that `FindPointerToType` returns a
pointer that points to the given type and not a duplicate type.
4) In scalar replacment, make sure the null constants that are created
are the correct type.
Adding basis of arithmetic merging
* Refactored constant collection in ConstantManager
* New rules:
* consecutive negates
* negate of arithmetic op with a constant
* consecutive muls
* reciprocal of div
* Removed IRContext::CanFoldFloatingPoint
* replaced by Instruction::IsFloatingPointFoldingAllowed
* Fixed some bad tests
* added some header comments
Added PerformIntegerOperation
* minor fixes to constants and tests
* fixed IntMultiplyBy1 to work with 64 bit ints
* added tests for integer mul merging
Adding test for vector integer multiply merging
Adding support for merging integer add and sub through negate
* Added tests
Adding rules to merge mult with preceding divide
* Has a couple tests, but needs more
* Added more comments
Fixed bug in integer division folding
* Will no longer merge through integer division if there would be a
remainder in the division
* Added a bunch more tests
Adding rules to merge divide and multiply through divide
* Improved comments
* Added tests
Adding rules to handle mul or div of a negation
* Added tests
Changes for review
* Early exit if no constants are involved in more functions
* fixed some comments
* removed unused declaration
* clarified some logic
Adding new rules for add and subtract
* Fold adds of adds, subtracts or negates
* Fold subtracts of adds, subtracts or negates
* Added tests
Implementation of the simplification pass.
- Create pass that calls the instruction folder on each instruction and
propagate instructions that fold to a copy. This will do copy
propagation as well.
- Did not use the propagator engine because I want to modify the instruction
as we go along.
- Change folding to not allocate new instructions, but make changes in
place. This change had a big impact on compile time.
- Add simplification pass to the legalization passes in place of
insert-extract elimination.
- Added test cases for new folding rules.
- Added tests for the simplification pass
- Added a method to the CFG to apply a function to the basic blocks in
reverse post order.
Contributes to #1164.
Create the folding engine that will
1) attempt to fold an instruction.
2) iterates on the folding so small folding rules can be easily combined.
3) insert new instructions when needed.
I've added the minimum number of rules needed to test the features above.
The current folding routines have a very cumbersome interface, make them
harder to use, and not a obvious how to extend.
This change is to create a new interface for the folding routines, and
show how it can be used by calling it from CCP.
This does not make a significant change to the behaviour of CCP. In
general it should produce the same code as before; however it is
possible that an instruction that takes 32-bit integers as inputs and
the result is not a 32-bit integer or bool will not be folded as before.
It seems like andriod has a problem with INT32_MAX and the like. I'll
explicitly define those if the are not already defined.
The current folding routines have a very cumbersome interface, make them
harder to use, and not a obvious how to extend.
This change is to create a new interface for the folding routines, and
show how it can be used by calling it from CCP.
This does not make a significant change to the behaviour of CCP. In
general it should produce the same code as before; however it is
possible that an instruction that takes 32-bit integers as inputs and
the result is not a 32-bit integer or bool will not be folded as before.
This addresses review feedback for the CCP implementation (which fixes
https://github.com/KhronosGroup/SPIRV-Tools/issues/889).
This adds more protection around the folding of instructions that would
not be supported by the folder.
This implements the conditional constant propagation pass proposed in
Constant propagation with conditional branches,
Wegman and Zadeck, ACM TOPLAS 13(2):181-210.
The main logic resides in CCPPass::VisitInstruction. Instruction that
may produce a constant value are evaluated with the constant folder. If
they produce a new constant, the instruction is considered interesting.
Otherwise, it's considered varying (for unfoldable instructions) or
just not interesting (when not enough operands have a constant value).
The other main piece of logic is in CCPPass::VisitBranch. This
evaluates the selector of the branch. When it's found to be a known
value, it computes the destination basic block and sets it. This tells
the propagator which branches to follow.
The patch required extensions to the constant manager as well. Instead
of hashing the Constant pointers, this patch changes the constant pool
to hash the contents of the Constant. This allows the lookups to be
done using the actual values of the Constant, preventing duplicate
definitions.
There are no functional changes in this patch. The generic folding
routines in FoldSpecConstantOpAndCompositePass are now inside opt/fold.{cpp,h}.
This code will be used by the upcoming constant propagation pass. In
time, we'll add more expression folding and simplification into these
two files.
