[MachineOutliner] Disable outlining from noreturn functions

Outlining from noreturn functions doesn't do the correct thing right now. The
outliner should respect that the caller is marked noreturn. In the event that
we have a noreturn function, and the outlined code is in tail position, the
outliner will not see that the outlined function should be tail called. As a
result, you end up with a regular call containing a return.

Fixing this requires that we check that all candidates live inside noreturn
functions. So, for the sake of correctness, don't outline from noreturn
functions right now.

Add machine-outliner-noreturn.mir to test this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@373791 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineOutliner.cpp b/lib/CodeGen/MachineOutliner.cpp
index 533cce57adc8444b519e1dc8663c39facc0ecc26..60eeefba9d6fef8b0a4d62d4bba5586252eb2601 100644 (file)
--- a/lib/CodeGen/MachineOutliner.cpp
+++ b/lib/CodeGen/MachineOutliner.cpp
@@ -1303,6 +1303,12 @@ void MachineOutliner::populateMapper(InstructionMapper &Mapper, Module &M,
     if (F.empty())
       continue;
 
+    // Disable outlining from noreturn functions right now. Noreturn requires
+    // special handling for the case where what we are outlining could be a
+    // tail call.
+    if (F.hasFnAttribute(Attribute::NoReturn))
+      continue;
+
     // There's something in F. Check if it has a MachineFunction associated with
     // it.
     MachineFunction *MF = MMI.getMachineFunction(F);

diff --git a/test/CodeGen/AArch64/machine-outliner-noreturn.mir b/test/CodeGen/AArch64/machine-outliner-noreturn.mir
new file mode 100644 (file)
index 0000000..29166f9
--- /dev/null
+++ b/test/CodeGen/AArch64/machine-outliner-noreturn.mir
@@ -0,0 +1,56 @@
+# RUN: llc -mtriple=aarch64-unknown-unknown -run-pass=machine-outliner -verify-machineinstrs %s -o - | FileCheck %s
+
+--- |
+  define void @foo() #0 { ret void }
+  define void @bar(i32 %a) #0 { ret void }
+  define void @baz(i32 %a) #0 { ret void }
+  attributes #0 = { noredzone noreturn }
+...
+---
+
+# Temporarily disable outlining from noreturn functions. To do this, we need
+# to verify thst every function we want to outline from is noreturn.
+
+# CHECK-NOT: OUTLINED_FUNCTION
+
+name:            foo
+alignment:       4
+tracksRegLiveness: true
+frameInfo:
+  maxAlignment:    1
+  maxCallFrameSize: 0
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    $w3 = ORRWri $wzr, 1
+    $w4 = ORRWri $wzr, 1
+    BRK 1
+...
+---
+name:            bar
+alignment:       4
+tracksRegLiveness: true
+frameInfo:
+  maxAlignment:    1
+  maxCallFrameSize: 0
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    $w3 = ORRWri $wzr, 1
+    $w4 = ORRWri $wzr, 1
+    BRK 1
+...
+---
+name:            baz
+alignment:       4
+tracksRegLiveness: true
+frameInfo:
+  maxAlignment:    1
+  maxCallFrameSize: 0
+machineFunctionInfo: {}
+body:             |
+  bb.0:
+    $w3 = ORRWri $wzr, 1
+    $w4 = ORRWri $wzr, 1
+    BRK 1
+...