[llvm] [RISCV][ISel] Add codegen support for the experimental zabha extension (PR #80192)

[Yingwei Zheng via llvm-commits]

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@@ -629,7 +629,10 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
 
   if (Subtarget.hasStdExtA()) {
     setMaxAtomicSizeInBitsSupported(Subtarget.getXLen());
-    setMinCmpXchgSizeInBits(32);
+    if (Subtarget.hasStdExtZabha())
+      setMinCmpXchgSizeInBits(8);
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dtcxzyw wrote:

Without this change, I cannot emit `amoxor.b/amoand.b/amoor.b` since AtomicExpand pass always widen them to 32-bit:

https://github.com/llvm/llvm-project/blob/995d21bc6ff2220b2887cf9640d936eb99b3c617/llvm/lib/CodeGen/AtomicExpandPass.cpp#L325-L333

Do you have any idea on how to fix it?


https://github.com/llvm/llvm-project/pull/80192