[llvm] [clang] [RISCV] Add experimental support of Zaamo and Zalrsc (PR #78970)

[Craig Topper via cfe-commits]

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+# RUN: not llvm-mc -triple riscv32 -mattr=+experimental-zaamo < %s 2>&1 | FileCheck %s
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topperc wrote:

Is this duplicating existing A test cases? If so can we split the A extension tests into 2 files as a pre-commit and add these the new Zaamo and Zalrsc command lines in this patch?

https://github.com/llvm/llvm-project/pull/78970