[llvm][RISCV] Do not assume V extension on seeing vector type. #166994
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We have a private extension which also uses the vector type in the frontend. Our platform does not have the V extension, so it triggered assertion failures from within getLMULCost(). I am not sure what is the best way to handle this, or if there are more such assertions within the codebase. But it feels reasonable to check for V extension before assuming LMUL exists.
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@llvm/pr-subscribers-backend-risc-v Author: Chenguang Wang (wecing) ChangesWe have a private extension which also uses the vector type in the frontend. Our platform does not have the V extension, so it triggered assertion failures from within getLMULCost(). I am not sure what is the best way to handle this, or if there are more such assertions within the codebase. But it feels reasonable to check for V extension before assuming LMUL exists. Full diff: https://github.com/llvm/llvm-project/pull/166994.diff 1 Files Affected:
diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
index 7bc0b5b394828..ababe42604ba5 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -2140,8 +2140,9 @@ InstructionCost RISCVTTIImpl::getMemoryOpCost(unsigned Opcode, Type *Src,
// Assume memory ops cost scale with the number of vector registers
// possible accessed by the instruction. Note that BasicTTI already
// handles the LT.first term for us.
- if (LT.second.isVector() && CostKind != TTI::TCK_CodeSize)
- BaseCost *= TLI->getLMULCost(LT.second);
+ if (TLI->getSubtarget().hasVInstructions())
+ if (LT.second.isVector() && CostKind != TTI::TCK_CodeSize)
+ BaseCost *= TLI->getLMULCost(LT.second);
return Cost + BaseCost;
}
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topperc
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Nov 7, 2025
vinay-deshmukh
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Nov 8, 2025
…166994) We have a private extension which also uses the vector type in the frontend. Our platform does not have the V extension, so it triggered assertion failures from within getLMULCost(). It feels reasonable to check for V extension before assuming LMUL exists.
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We have a private extension which also uses the vector type in the frontend. Our platform does not have the V extension, so it triggered assertion failures from within getLMULCost().
I am not sure what is the best way to handle this, or if there are more such assertions within the codebase. But it feels reasonable to check for V extension before assuming LMUL exists.