[llvm] r192124 - [mips] Disable tail merging when long branch pass is enabled.

[Akira Hatanaka]

Author: ahatanak
Date: Mon Oct  7 14:13:53 2013
New Revision: 192124

URL: http://llvm.org/viewvc/llvm-project?rev=192124&view=rev
Log:
[mips] Disable tail merging when long branch pass is enabled.

Modified:
    llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp

Modified: llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp?rev=192124&r1=192123&r2=192124&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp Mon Oct  7 14:13:53 2013
@@ -135,7 +135,13 @@ namespace {
 class MipsPassConfig : public TargetPassConfig {
 public:
   MipsPassConfig(MipsTargetMachine *TM, PassManagerBase &PM)
-    : TargetPassConfig(TM, PM) {}
+    : TargetPassConfig(TM, PM) {
+    // The current implementation of long branch pass requires a scratch
+    // register ($at) to be available before branch instructions. Tail merging
+    // can break this requirement, so disable it when long branch pass is
+    // enabled.
+    EnableTailMerge = !getMipsSubtarget().enableLongBranchPass();
+  }
 
   MipsTargetMachine &getMipsTargetMachine() const {
     return getTM<MipsTargetMachine>();