[llvm] [RISCV][GISEL] Add legalizer for G_BSWAP (PR #70226)

[Michael Maitland via llvm-commits]

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@@ -81,6 +81,11 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST) {
         .clampScalar(BigTyIdx, XLenLLT, XLenLLT);
   }
 
+  getActionDefinitionsBuilder(G_BSWAP)
+    .widenScalarToNextPow2(0)
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michaelmaitland wrote:

widenScalarToNextPow2 I grabbed from AArch64 who does not seem to be testing it as well. I agree that we can drop it because the intrinsic documentation says it will always be a power of 2. The clampScalar I think is needed in the case that there is a bswap.i64 on rv32? The last commit shows the impact on the diff. Do you think it was correct before the last commit?

https://github.com/llvm/llvm-project/pull/70226