Splitting SMULWB and SMULWT instruction selection changes from D30044 into separate patch. ISel has been moved from DAGToDAG into combine and so the related SMLAWB and SMLAWT instructions can be selected in tablegen. The helper functions have been removed from the original patch too.
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Please add some testcases covering the improved isS16 function.
lib/Target/ARM/ARMISelLowering.cpp | ||
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1482 | Add a comment describing what exactly this function is checking for? It's not obvious why a function called "isS16" is special-casing SRA nodes. | |
9967 | getResNo, maybe? | |
11835 | You could also simplify SMULWT nodes in a similar manner. |
Hi Eli,
I've added a comment to isS16, slightly simplified the node selection and added a simplifyTop16 function for SMULWT. I've also added a couple of test for loading i16 values.
cheers,
sam
lib/Target/ARM/ARMISelLowering.cpp | ||
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1497 | Explicitly passing "true" is probably a bad idea here. | |
1499 | You probably want to use TargetLowering::SimplifyDemandedBits rather than TargetLoweringOpt::SimplifyDemandedBits; the latter has weird handling for nodes with multiple uses. I count eight nearly identical copies of this code, with just varying demanded bits; two here, combineBT in X86ISelLowering, two in XCoreTargetLowering::PerformDAGCombine, SITargetLowering::performCvtF32UByteNCombine, performTBISimplification in AArch64ISelLowering.cpp, simplifyI24 in AMDGPUISelLowering.cpp. Please add a helper to TargetLowering for all of these to use. (Don't worry about fixing the other copies in this patch.) |
lib/CodeGen/SelectionDAG/TargetLowering.cpp | ||
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475 ↗ | (On Diff #91146) | You can unify SimplifyDemandedLowBits and SimplifyDemandedHighBits by adding one function that takes the DemandedMask as an argument. |
Yes ok, I had hoped that more code could be refactored out of the other backends since most of the uses were for low bit masks, but it makes more sense to a flexible API. This makes the interface very similar to TLO::SimplifyDemandedBits, do you know why that function is set to assume a single use?
LGTM.
This makes the interface very similar to TLO::SimplifyDemandedBits, do you know why that function is set to assume a single use?
The function has exactly one user in lib/Target/AMDGPU/AMDGPUISelLowering.cpp, and the behavior is necessary there. (I haven't really carefully considered the consequences of it.)
Add a comment describing what exactly this function is checking for? It's not obvious why a function called "isS16" is special-casing SRA nodes.