[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294527 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -3156,7 +3156,8 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
     }
 
     if (VA.isRegLoc()) {
-      if (realArgIdx == 0 && Flags.isReturned() && Outs[0].VT == MVT::i64) {
+      if (realArgIdx == 0 && Flags.isReturned() && !Flags.isSwiftSelf() &&
+          Outs[0].VT == MVT::i64) {
         assert(VA.getLocVT() == MVT::i64 &&
                "unexpected calling convention register assignment");
         assert(!Ins.empty() && Ins[0].VT == MVT::i64 &&

lib/Target/ARM/ARMISelLowering.cpp

@@ -1826,7 +1826,8 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
                          StackPtr, MemOpChains, Flags);
       }
     } else if (VA.isRegLoc()) {
-      if (realArgIdx == 0 && Flags.isReturned() && Outs[0].VT == MVT::i32) {
+      if (realArgIdx == 0 && Flags.isReturned() && !Flags.isSwiftSelf() &&
+          Outs[0].VT == MVT::i32) {
         assert(VA.getLocVT() == MVT::i32 &&
                "unexpected calling convention register assignment");
         assert(!Ins.empty() && Ins[0].VT == MVT::i32 &&

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
+}

test/CodeGen/ARM/swiftself.ll

@@ -63,3 +63,20 @@ define i8* @swiftself_notail(i8* swiftself %addr0, i8* %addr1) nounwind "no-fram
   %res = tail call i8* @swiftself_param(i8* swiftself %addr1)
   ret i8* %res
 }
+
+; We cannot pretend that 'r0' 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 r0.
+declare swiftcc i8* @thisreturn_attribute(i8* returned swiftself)
+; OPT-LABEL: swiftself_nothisreturn:
+; OPT-DAG: mov [[CSREG:r[1-9].*]], r0
+; OPT-DAG: ldr r10, [r10]
+; OPT: bl  {{_?}}thisreturn_attribute
+; OPT: str r0, {{\[}}[[CSREG]]
+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
+}