[clang] [llvm] [AArch64] Support preserve_none calling convention (PR #91046)

[via cfe-commits]

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@@ -494,6 +494,29 @@ def CC_AArch64_GHC : CallingConv<[
   CCIfType<[i64], CCAssignToReg<[X19, X20, X21, X22, X23, X24, X25, X26, X27, X28]>>
 ]>;
 
+let Entry = 1 in
+def CC_AArch64_Preserve_None : CallingConv<[
+    // We only preserve:
+    // - X18, which is used for the 'nest' parameter.
+    // - X29, the frame pointer
+    // - X30, the link register
+    // All other registers can be used to pass arguments.
+    // Non-volatile registers are used first, so functions may call
+    // normal functions without saving and reloading arguments.
+    CCIfType<[i32], CCAssignToReg<[W19, W20, W21, W22, W23,
+                                   W24, W25, W26, W27, W28,
+                                   W0, W1, W2, W3, W4, W5,
+                                   W6, W7, W8, W9, W10, W11,
+                                   W12, W13, W14, W15, W16, W17]>>,
+    CCIfType<[i64], CCAssignToReg<[X19, X20, X21, X22, X23,
+                                   X24, X25, X26, X27, X28,
+                                   X0, X1, X2, X3, X4, X5,
+                                   X6, X7, X8, X9, X10, X11,
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weiguozhi wrote:

X8 is used to pass SRet parameter in AArch64_Common, so it can not be used as a general argument register.

https://github.com/llvm/llvm-project/pull/91046