[llvm] [ARM] Use FPRegs for fastcc calling convention detection. (PR #184593)

[Simon Tatham via llvm-commits]

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@@ -0,0 +1,23 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; RUN: llc -mtriple=thumbv8.1m.main-none-none-eabihf -mattr=+mve -verify-machineinstrs %s -o - | FileCheck %s
+
+%struct.S51 = type { <16 x i8>, <16 x i8> }
+
+define internal %struct.S51 @F33() {
+; CHECK-LABEL: F33:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    vmov.i32 q0, #0x0
+; CHECK-NEXT:    vmov.i32 q1, #0x0
+; CHECK-NEXT:    bx lr
+entry:
+  ret %struct.S51 zeroinitializer
+}
+
+define internal fastcc void @F32() {
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statham-arm wrote:

I see that the linked bug ticket is specifically about tailcalls from a fastcc function to a normal one, but this patch is also changing the calling convention in fastcc functions that don't tailcall, so should we also have a simpler test case where you make a fastcc version of `@F33` here, and demonstrate that that by itself uses the q registers?

https://github.com/llvm/llvm-project/pull/184593