[ADT] Add APIntOps::mulhs / APIntOps::mulhu

[RKSimon]

• Move implementations from SelectionDAG.cpp FoldValue into APInt.h APIntOps
  

  llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

  Lines 6012 to 6016 in deff460

  	case ISD::MULHS: {
  	unsigned FullWidth = C1.getBitWidth() * 2;
  	APInt C1Ext = C1.sext(FullWidth);
  	APInt C2Ext = C2.sext(FullWidth);
  	return (C1Ext * C2Ext).extractBits(C1.getBitWidth(), C1.getBitWidth());

  
  

  llvm-project/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

  Lines 6018 to 6022 in deff460

  	case ISD::MULHU: {
  	unsigned FullWidth = C1.getBitWidth() * 2;
  	APInt C1Ext = C1.zext(FullWidth);
  	APInt C2Ext = C2.zext(FullWidth);
  	return (C1Ext * C2Ext).extractBits(C1.getBitWidth(), C1.getBitWidth());

• Add APIntTest unit test coverage

• Update DivisionByConstantTest.cpp (this might require the lhs/rhs operands to be extended to the same bitwidth)

• Update KnownBitsTest.cpp to use APIntOps::mulhs/u in exhaustive tests

• Update mlir ArithOps.cpp + SPIRVCanonicalization.cpp to use APIntOps::mulhs/mulhu

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. In the comments of the issue, request for it to be assigned to you.
2. Fix the issue locally.
3. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
4. Create a Git commit.
5. Run git clang-format HEAD~1 to format your changes.
6. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Simon Pilgrim (RKSimon)

- [ ] Move implementations from SelectionDAG.cpp FoldValue into APInt.h APIntOps https://github.com/llvm/llvm-project/blob/deff460b46dfcc8d6d5917a2b78c0d52edbe4afb/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp#L6012-L6016 https://github.com/llvm/llvm-project/blob/deff460b46dfcc8d6d5917a2b78c0d52edbe4afb/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp#L6018-L6022

• Add APIntTest unit test coverage
• Update DivisionByConstantTest.cpp
• Update KnownBitsTest.cpp to use APIntOps::mulhs/u in exhaustive tests

[Atousa]

@RKSimon I am interested in working on this issue. Please assign it to me.

[EugeneZelenko]

@Atousa: Just create pull request and mention it on this page.

[Sh0g0-1758]

Hey there, I am also interested in working on this. I will link a PR soon. @Atousa , since you are assigned the issue, if you have not done significant work on this, can we collaborate?

[Atousa]

@RKSimon @Sh0g0-1758 this is just assigned to me and I am working on it. This is not collaborative!

[Sh0g0-1758]

Hm... I saw no PR for 3 days and the solution was rather simple, so thought of working on it. Anyways, if you do not wish to collaborate, that is fine. Please link a PR and I will close mine. Though, @RKSimon, I suppose there is no harm in 2 people working on this issue. P.S., the checks are passing.

[Sh0g0-1758]

Just out of curiosity, @RKSimon, in the 4th task, you mentioned updating KnownBitsTest.cpp but In it, we are using KnownBits::mul. I don't think I was supposed to update it, so could you please clarify as to what you meant?

[RKSimon]

Just out of curiosity, @RKSimon, in the 4th task, you mentioned updating KnownBitsTest.cpp but In it, we are using KnownBits::mul. I don't think I was supposed to update it, so could you please clarify as to what you meant?

I meant the APInt reference version in the exhaustive tests

llvm-project/llvm/unittests/Support/KnownBitsTest.cpp

Lines 540 to 543 in deff460

	[](const APInt &N1, const APInt &N2) {
	unsigned Bits = N1.getBitWidth();
	return (N1.sext(2 * Bits) * N2.sext(2 * Bits)).extractBits(Bits, Bits);
	},

[RKSimon]

BTW @Sh0g0-1758 I thought @Atousa was working on this ticket?

[Sh0g0-1758]

Well yeah, she still can, I don't mind closing my PR, but I do believe that most of the work is done. I guess this sums it up : #84207 (comment)