[llvm] [X86] Clear regcall arg aliases in dynamic CSR masks (PR #225262)

[Aochang Liu via llvm-commits]

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@@ -1167,8 +1167,9 @@ SDValue X86TargetLowering::LowerCallResult(
     // In some calling conventions we need to remove the used registers
     // from the register mask.
     if (RegMask) {
-      for (MCPhysReg SubReg : TRI->subregs_inclusive(VA.getLocReg()))
-        RegMask[SubReg / 32] &= ~(1u << (SubReg % 32));
+      for (MCRegAliasIterator Alias(VA.getLocReg(), TRI, true); Alias.isValid();
+           ++Alias)
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HelloWorldU wrote:

The new test covers the argument mask, but `@callee` returns void. Is there a return-register case that exercises this change?

https://github.com/llvm/llvm-project/pull/225262