Generate PPC early conditional returns
PowerPC has a conditional branch to the link register (return) instruction: BCLR.
This should be used any time when we'd otherwise have a conditional branch to a
return. This adds a small pass, PPCEarlyReturn, which runs just prior to the
branch selection pass (and, importantly, after block placement) to generate
these conditional returns when possible. It will also eliminate unconditional
branches to returns (these happen rarely; most of the time these have already
been tail duplicated by the time PPCEarlyReturn is invoked). This is a nice
optimization for small functions that do not maintain a stack frame.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179026 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/PPCInstrInfo.td b/lib/Target/PowerPC/PPCInstrInfo.td
index 142abe1..37b1a0b 100644
--- a/lib/Target/PowerPC/PPCInstrInfo.td
+++ b/lib/Target/PowerPC/PPCInstrInfo.td
@@ -511,10 +511,14 @@
// BCC represents an arbitrary conditional branch on a predicate.
// FIXME: should be able to write a pattern for PPCcondbranch, but can't use
// a two-value operand where a dag node expects two operands. :(
- let isCodeGenOnly = 1 in
+ let isCodeGenOnly = 1 in {
def BCC : BForm<16, 0, 0, (outs), (ins pred:$cond, condbrtarget:$dst),
"b${cond:cc} ${cond:reg}, $dst"
/*[(PPCcondbranch CRRC:$crS, imm:$opc, bb:$dst)]*/>;
+ let isReturn = 1, Uses = [LR, RM] in
+ def BCLR : XLForm_2_br<19, 16, 0, (outs), (ins pred:$cond),
+ "b${cond:cc}lr ${cond:reg}", BrB, []>;
+ }
let Defs = [CTR], Uses = [CTR] in {
def BDZ : BForm_1<16, 18, 0, 0, (outs), (ins condbrtarget:$dst),