[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
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.h b/llvm/lib/Target/SystemZ/SystemZInstrInfo.h
index 06ed3eb..baa126f 100644
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.h
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.h
@@ -111,6 +111,16 @@
const MachineOperand *target)
: Type(type), CCValid(ccValid), CCMask(ccMask), Target(target) {}
};
+// Kinds of branch in compare-and-branch instructions. Together with type
+// of the converted compare, this identifies the compare-and-branch
+// instruction.
+enum CompareAndBranchType {
+ // Relative branch - CRJ etc.
+ CompareAndBranch,
+
+ // Indirect branch, used for return - CRBReturn etc.
+ CompareAndReturn
+};
} // end namespace SystemZII
class SystemZSubtarget;
@@ -165,6 +175,8 @@
MachineBasicBlock &FMBB,
unsigned NumCyclesF, unsigned ExtraPredCyclesF,
BranchProbability Probability) const override;
+ bool isProfitableToDupForIfCvt(MachineBasicBlock &MBB, unsigned NumCycles,
+ BranchProbability Probability) const override;
bool PredicateInstruction(MachineInstr &MI,
ArrayRef<MachineOperand> Pred) const override;
void copyPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
@@ -233,6 +245,7 @@
// BRANCH exists, return the opcode for the latter, otherwise return 0.
// MI, if nonnull, is the compare instruction.
unsigned getCompareAndBranch(unsigned Opcode,
+ SystemZII::CompareAndBranchType Type,
const MachineInstr *MI = nullptr) const;
// Emit code before MBBI in MI to move immediate value Value into