Materialize global addresses via movt/movw pair, this is always better
than doing the same via constpool:
1. Load from constpool costs 3 cycles on A9, movt/movw pair - just 2.
2. Load from constpool might stall up to 300 cycles due to cache miss.
3. Movt/movw does not use load/store unit.
4. Less constpool entries => better compiler performance.
This is only enabled on ELF systems, since darwin does not have needed
relocations (yet).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89720 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 1549b63..c839fc6 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -39,6 +39,7 @@
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/ADT/VectorExtras.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include <sstream>
@@ -1356,10 +1357,17 @@
PseudoSourceValue::getGOT(), 0);
return Result;
} else {
- SDValue CPAddr = DAG.getTargetConstantPool(GV, PtrVT, 4);
- CPAddr = DAG.getNode(ARMISD::Wrapper, dl, MVT::i32, CPAddr);
- return DAG.getLoad(PtrVT, dl, DAG.getEntryNode(), CPAddr,
- PseudoSourceValue::getConstantPool(), 0);
+ // If we have T2 ops, we can materialize the address directly via movt/movw
+ // pair. This is always cheaper.
+ if (Subtarget->useMovt()) {
+ return DAG.getNode(ARMISD::Wrapper, dl, PtrVT,
+ DAG.getTargetGlobalAddress(GV, PtrVT));
+ } else {
+ SDValue CPAddr = DAG.getTargetConstantPool(GV, PtrVT, 4);
+ CPAddr = DAG.getNode(ARMISD::Wrapper, dl, MVT::i32, CPAddr);
+ return DAG.getLoad(PtrVT, dl, DAG.getEntryNode(), CPAddr,
+ PseudoSourceValue::getConstantPool(), 0);
+ }
}
}