LivePhysRegs: Fix live-outs of return blocks

I realized that the live-out set computed for the return block is
missing the callee saved registers (the non-pristine ones to be exact).

This only affects the liveness computed for instructions inside the
function epilogue which currently none of the LivePhysRegs users in llvm
cares about, so this is just a drive-by fix without a testcase.

Differential Revision: http://reviews.llvm.org/D13180

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248636 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/LivePhysRegs.h b/include/llvm/CodeGen/LivePhysRegs.h
index 326aebfcd94e2f39071b2689c7c7e59c5410d1c3..3bdf5ae8d0132075a3f96d6d23531f0c890c59bb 100644 (file)
--- a/include/llvm/CodeGen/LivePhysRegs.h
+++ b/include/llvm/CodeGen/LivePhysRegs.h
@@ -122,9 +122,9 @@ public:
   void addLiveIns(const MachineBasicBlock *MBB, bool AddPristines = false);
 
   /// \brief Adds all live-out registers of basic block @p MBB; After prologue/
-  /// epilogue insertion \p AddPristines should be set to true to insert the
-  /// pristine registers.
-  void addLiveOuts(const MachineBasicBlock *MBB, bool AddPristines = false);
+  /// epilogue insertion \p AddPristinesAndCSRs should be set to true.
+  void addLiveOuts(const MachineBasicBlock *MBB,
+                   bool AddPristinesAndCSRs = false);
 
   typedef SparseSet<unsigned>::const_iterator const_iterator;
   const_iterator begin() const { return LiveRegs.begin(); }

diff --git a/lib/CodeGen/LivePhysRegs.cpp b/lib/CodeGen/LivePhysRegs.cpp
index 61226b7472acf20d3208c2afede8aeb990ce81e0..efbbcbe23e1501c548dd28765dac28ab23993c80 100644 (file)
--- a/lib/CodeGen/LivePhysRegs.cpp
+++ b/lib/CodeGen/LivePhysRegs.cpp
@@ -147,11 +147,19 @@ static void addPristines(LivePhysRegs &LiveRegs, const MachineFunction &MF,
 }
 
 void LivePhysRegs::addLiveOuts(const MachineBasicBlock *MBB,
-                               bool AddPristines) {
-  if (AddPristines) {
+                               bool AddPristinesAndCSRs) {
+  if (AddPristinesAndCSRs) {
     const MachineFunction &MF = *MBB->getParent();
     addPristines(*this, MF, *TRI);
+    if (!MBB->isReturnBlock()) {
+      // The return block has no successors whose live-ins we could merge
+      // below. So instead we add the callee saved registers manually.
+      for (const MCPhysReg *I = TRI->getCalleeSavedRegs(&MF); *I; ++I)
+        addReg(*I);
+    }
   }
+
+  // To get the live-outs we simply merge the live-ins of all successors.
   for (const MachineBasicBlock *Succ : MBB->successors())
     ::addLiveIns(*this, *Succ);
 }