From: Chris Lattner <sabre@nondot.org>
Date: Mon, 10 Mar 2008 23:34:12 +0000 (+0000)
Subject: Don't emit FP_REG_KILL into a block that just returns.  Nothing
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=03fdec04d1f179f32047aa6752aa59f2674c9894;p=oota-llvm.git

Don't emit FP_REG_KILL into a block that just returns.  Nothing
can be live out of the block anyway, so it isn't needed.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48192 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index 6036dcbf2e0..a4da5415883 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -550,7 +550,8 @@ void X86DAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
 
   DAG.RemoveDeadNodes();
 
-  // Emit machine code to BB. 
+  // Emit machine code to BB.  This can change 'BB' to the last block being 
+  // inserted into.
   ScheduleAndEmitDAG(DAG);
   
   // If we are emitting FP stack code, scan the basic block to determine if this
@@ -566,15 +567,27 @@ void X86DAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
   // Scan all of the machine instructions in these MBBs, checking for FP
   // stores.  (RFP32 and RFP64 will not exist in SSE mode, but RFP80 might.)
   MachineFunction::iterator MBBI = FirstMBB;
-  do {
+  MachineFunction::iterator EndMBB = BB; ++EndMBB;
+  for (; MBBI != EndMBB; ++MBBI) {
+    MachineBasicBlock *MBB = MBBI;
+    
+    // If this block returns, ignore it.  We don't want to insert an FP_REG_KILL
+    // before the return.
+    if (!MBB->empty()) {
+      MachineBasicBlock::iterator EndI = MBB->end();
+      --EndI;
+      if (EndI->getDesc().isReturn())
+        continue;
+    }
+    
     bool ContainsFPCode = false;
-    for (MachineBasicBlock::iterator I = MBBI->begin(), E = MBBI->end();
+    for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
          !ContainsFPCode && I != E; ++I) {
       if (I->getNumOperands() != 0 && I->getOperand(0).isRegister()) {
         const TargetRegisterClass *clas;
         for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op) {
           if (I->getOperand(op).isRegister() && I->getOperand(op).isDef() &&
-              TargetRegisterInfo::isVirtualRegister(I->getOperand(op).getReg()) &&
+            TargetRegisterInfo::isVirtualRegister(I->getOperand(op).getReg()) &&
               ((clas = RegInfo->getRegClass(I->getOperand(0).getReg())) == 
                  X86::RFP32RegisterClass ||
                clas == X86::RFP64RegisterClass ||
@@ -608,11 +621,11 @@ void X86DAGToDAGISel::InstructionSelectBasicBlock(SelectionDAG &DAG) {
     }
     // Finally, if we found any FP code, emit the FP_REG_KILL instruction.
     if (ContainsFPCode) {
-      BuildMI(*MBBI, MBBI->getFirstTerminator(),
+      BuildMI(*MBB, MBBI->getFirstTerminator(),
               TM.getInstrInfo()->get(X86::FP_REG_KILL));
       ++NumFPKill;
     }
-  } while (&*(MBBI++) != BB);
+  }
 }
 
 /// EmitSpecialCodeForMain - Emit any code that needs to be executed only in
diff --git a/test/CodeGen/X86/2007-07-25-EpilogueBug.ll b/test/CodeGen/X86/2007-07-25-EpilogueBug.ll
index f0308bd63be..ddac6ce217d 100644
--- a/test/CodeGen/X86/2007-07-25-EpilogueBug.ll
+++ b/test/CodeGen/X86/2007-07-25-EpilogueBug.ll
@@ -1,5 +1,7 @@
+; Verify that the addl comes before any popl.
+
 ; RUN: llvm-as < %s | llc -mtriple=i686-pc-linux-gnu -mcpu=i386 | \
-; RUN:   %prcontext ret 1 | grep FP_REG_KILL
+; RUN:   %prcontext ret 1 | grep popl
 ; PR1573
 
 	%struct.c34006f__TsB = type { i8, i32, i32, %struct.c34006f__TsB___b___XVN }