[llvm] [AArch64] Assert `expandMOVImm` prioritizes optimal single MOVZ/N (PR #169341)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-aarch64

Author: Tomer Shafir (tomershafir)

<details>
<summary>Changes</summary>

The expansion of move immediate in `expandMOVImm` follows the priority of the `MOV` alias. In addition, the selection there properly prefers expansion based on perf optimality order. This change adds a simple assert that `expandMOVImmSimple` expands a single optimal MOVZ/MOVK.

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Full diff: https://github.com/llvm/llvm-project/pull/169341.diff


1 Files Affected:

- (modified) llvm/lib/Target/AArch64/AArch64ExpandImm.cpp (+2) 


``````````diff
diff --git a/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp b/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp
index e9660ac140301..ae5818419cba5 100644
--- a/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ExpandImm.cpp
@@ -549,6 +549,8 @@ void AArch64_IMM::expandMOVImm(uint64_t Imm, unsigned BitSize,
   // Prefer MOVZ/MOVN over ORR because of the rules for the "mov" alias.
   if ((BitSize / 16) - OneChunks <= 1 || (BitSize / 16) - ZeroChunks <= 1) {
     expandMOVImmSimple(Imm, BitSize, OneChunks, ZeroChunks, Insn);
+    assert(Insn.size() == 1 &&
+           "Move of immediate should have expanded to a single MOVZ/MOVN");
     return;
   }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/169341