[PowerPC] Bail out of FISel when lowering long calls

We currently don't handle tail calls in fast-isel but
we continue with the lowering when -mlongcall is
specified and lower the calls normally. We should
defer to SDISel for this so that it is lowered correctly.

Differential revision: https://reviews.llvm.org/D123997

llvm/lib/Target/PowerPC/PPCFastISel.cpp

@@ -1555,8 +1555,8 @@ bool PPCFastISel::fastLowerCall(CallLoweringInfo &CLI) {
   if (!Callee && !Symbol)
     return false;
 
-  // Allow SelectionDAG isel to handle tail calls.
-  if (IsTailCall)
+  // Allow SelectionDAG isel to handle tail calls and long calls.
+  if (IsTailCall || Subtarget->useLongCalls())
     return false;
 
   // Let SDISel handle vararg functions.

llvm/test/CodeGen/PowerPC/longcall.ll

@@ -1,14 +1,29 @@
 ; RUN: llc < %s | FileCheck %s
+; RUN: llc --fast-isel < %s | FileCheck %s
 target datalayout = "E-m:e-i64:64-n32:64"
 target triple = "powerpc64-unknown-linux-gnu"
 
 ; Function Attrs: nounwind
-define void @bar() local_unnamed_addr #0 {
+define void @tail() local_unnamed_addr #0 {
 entry:
   tail call void @foo() #1
   ret void
 
-; CHECK-LABEL: @bar
+; CHECK-LABEL: @tail
+; CHECK: ld [[FD:[0-9]+]], .LC0@toc@l({{[0-9]+}})
+; CHECK: ld [[ADDR:[0-9]+]], 0([[FD]])
+; CHECK: mtctr [[ADDR]]
+; CHECK: bctrl
+; CHECK-NOT: bl foo
+; CHECK: blr
+}
+
+define void @notail() local_unnamed_addr #0 {
+entry:
+  call void @foo() #1
+  ret void
+
+; CHECK-LABEL: @notail
 ; CHECK: ld [[FD:[0-9]+]], .LC0@toc@l({{[0-9]+}})
 ; CHECK: ld [[ADDR:[0-9]+]], 0([[FD]])
 ; CHECK: mtctr [[ADDR]]