[SystemZ] Implement conditional returns

Return is now considered a predicable instruction, and is converted
to a newly-added CondReturn (which maps to BCR to %r14) instruction by
the if conversion pass.

Also, fused compare-and-branch transform knows about conditional
returns, emitting the proper fused instructions for them.

This transform triggers on a *lot* of tests, hence the huge diffstat.
The changes are mostly jX to br %r14 -> bXr %r14.

Author: koriakin

Differential Revision: http://reviews.llvm.org/D17339

llvm-svn: 265689

1 files changed, 1 insertions, 2 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp b/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
index f305e85f6cf..baa6907764a 100644
--- a/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp
@@ -125,8 +125,7 @@ bool SystemZPassConfig::addInstSelector() {
 }
 
 void SystemZPassConfig::addPreSched2() {
-  if (getOptLevel() != CodeGenOpt::None &&
-      getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
+  if (getOptLevel() != CodeGenOpt::None)
     addPass(&IfConverterID);
 }