[llvm] [RISCV][GlobalISel] Legalize Scalable Vector Loads and Stores (PR #84965)

[Michael Maitland via llvm-commits]

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@@ -3690,7 +3690,7 @@ LegalizerHelper::LegalizeResult LegalizerHelper::lowerLoad(GAnyLoad &LoadMI) {
 
   if (!isPowerOf2_32(MemSizeInBits)) {
     // This load needs splitting into power of 2 sized loads.
-    LargeSplitSize = llvm::bit_floor(MemSizeInBits);
+    LargeSplitSize = llvm::bit_floor(MemSizeInBits.getKnownMinValue());
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michaelmaitland wrote:

These values are used in the call to getMachineMemOperand. There is a signature:
```
MachineMemOperand *MachineFunction::getMachineMemOperand(
    const MachineMemOperand *MMO, const MachinePointerInfo &PtrInfo, LLT Ty)
```
It might be safer to create a scalable MMO using `Ty` rather than forcing it into fixed.

Ditto for the other instructions that are built with `LargeSplitSize` and `SmallSplitSize`.

https://github.com/llvm/llvm-project/pull/84965