[AAarch64] Optimize CSINC-branch sequence
Peephole optimization that generates a single conditional branch
for csinc-branch sequences like in the examples below. This is
possible when the csinc sets or clears a register based on a condition
code and the branch checks that register. Also the condition
code may not be modified between the csinc and the original branch.
Examples:
1. Convert csinc w9, wzr, wzr, <CC>;tbnz w9, #0, 0x44
to b.<invCC>
2. Convert csinc w9, wzr, wzr, <CC>; tbz w9, #0, 0x44
to b.<CC>
rdar://problem/18506500
llvm-svn: 219742
diff --git a/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
index 7c195a8..90a4dcf 100644
--- a/llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -135,6 +135,7 @@
bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
SmallPtrSetImpl<MachineInstr*> &LocalMIs);
bool optimizeSelect(MachineInstr *MI);
+ bool optimizeCondBranch(MachineInstr *MI);
bool optimizeCopyOrBitcast(MachineInstr *MI);
bool optimizeCoalescableCopy(MachineInstr *MI);
bool optimizeUncoalescableCopy(MachineInstr *MI,
@@ -498,6 +499,12 @@
return true;
}
+/// \brief Check if a simpler conditional branch can be
+// generated
+bool PeepholeOptimizer::optimizeCondBranch(MachineInstr *MI) {
+ return TII->optimizeCondBranch(MI);
+}
+
/// \brief Check if the registers defined by the pair (RegisterClass, SubReg)
/// share the same register file.
static bool shareSameRegisterFile(const TargetRegisterInfo &TRI,
@@ -1104,6 +1111,11 @@
continue;
}
+ if (MI->isConditionalBranch() && optimizeCondBranch(MI)) {
+ Changed = true;
+ continue;
+ }
+
if (isCoalescableCopy(*MI) && optimizeCoalescableCopy(MI)) {
// MI is just rewritten.
Changed = true;