[ARM/AArch ISel] SwiftCC: First parameters that are marked swiftself are not 'this returns'

We mark X0 as preserved by a call that passes the returned parameter.

 x0 = ...
 fun(x0) // no implicit def of x0

This no longer is valid if we pass the parameter in a different register then
the returned value as is the case with a swiftself parameter (passed in x20).

x20 = ...
fun(x20) // there should be an implict def of x8

rdar://30425845

llvm-svn: 294527

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/AArch64/swiftself.ll b/llvm/test/CodeGen/AArch64/swiftself.ll
index a60aed6b0f2..33a49198430 100644
--- a/llvm/test/CodeGen/AArch64/swiftself.ll
+++ b/llvm/test/CodeGen/AArch64/swiftself.ll
@@ -65,3 +65,21 @@ define i8* @swiftself_notail(i8* swiftself %addr0, i8* %addr1) nounwind {
   %res = tail call i8* @swiftself_param(i8* swiftself %addr1)
   ret i8* %res
 }
+
+; We cannot pretend that 'x0' is alive across the thisreturn_attribute call as
+; we normally would. We marked the first parameter with swiftself which means it
+; will no longer be passed in x0.
+declare swiftcc i8* @thisreturn_attribute(i8* returned swiftself)
+; OPT-LABEL: swiftself_nothisreturn:
+; OPT-DAG: ldr  x20, [x20]
+; OPT-DAG: mov [[CSREG:x[1-9].*]], x8
+; OPT: bl {{_?}}thisreturn_attribute
+; OPT: str x0, {{\[}}[[CSREG]]
+; OPT: ret
+define hidden swiftcc void @swiftself_nothisreturn(i8** noalias nocapture sret, i8** noalias nocapture readonly swiftself) {
+entry:
+  %2 = load i8*, i8** %1, align 8
+  %3 = tail call swiftcc i8* @thisreturn_attribute(i8* swiftself %2)
+  store i8* %3, i8** %0, align 8
+  ret void
+}