[PowerPC] Bail out of FISel when lowering long calls

[nemanjai]

Summary

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.

[umesh.kalappa0]

@nemanjai ,thank you for quick fix and please checkout the unit test failed ?

[nemanjai]

In D123997#3461035, @umesh.kalappa0 wrote:

@nemanjai ,thank you for quick fix and please checkout the unit test failed ?

The unit test failure should be unrelated. A change in code generation for PowerPC should not cause a sanitizer failure on X86.

[umesh.kalappa0]

In D123997#3463602, @nemanjai wrote:

In D123997#3461035, @umesh.kalappa0 wrote:

@nemanjai ,thank you for quick fix and please checkout the unit test failed ?

The unit test failure should be unrelated. A change in code generation for PowerPC should not cause a sanitizer failure on X86.

I'm ok with the changes .

[amyk]

LGTM.

[umesh.kalappa0]

LGTM too.

llvm/lib/Target/PowerPC/PPCFastISel.cpp

bool PPCFastISel::fastLowerCall(CallLoweringInfo &CLI) {
   bool IsTailCall     = CLI.IsTailCall;
   bool IsVarArg       = CLI.IsVarArg;
   const Value *Callee = CLI.Callee;
   const MCSymbol *Symbol = CLI.Symbol;
 
   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.
   if (IsVarArg)
     return false;
 
   // If this is a PC-Rel function, let SDISel handle the call.
   if (Subtarget->isUsingPCRelativeCalls())

llvm/test/CodeGen/PowerPC/longcall.ll

 ; 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]]
 ; CHECK: bctrl
 ; CHECK-NOT: bl foo
 ; CHECK: blr
 }
 
 ; CHECK: .tc foo
 
 declare void @foo() local_unnamed_addr
 
 attributes #0 = { nounwind "target-cpu"="ppc64" "target-features"="+longcall" }
 attributes #1 = { nounwind }