[LoopStrenghtReduce] Refactoring and addition of a new target cost function.

Refactored so that a LSRUse owns its fixups, as oppsed to letting the
LSRInstance own them. This makes it easier to rate formulas for
LSRUses, since the fixups are available directly. The Offsets vector
has been removed since it was no longer necessary.

New target hook isFoldableMemAccessOffset(), which is used during formula
rating.

For SystemZ, this is useful to express that loads and stores with
float or vector types with a big/negative offset should be avoided in
loops. Without this, LSR will generate a lot of negative offsets that
would require extra instructions for loading the address.

Updated tests:
test/CodeGen/SystemZ/loop-01.ll

Reviewed by: Quentin Colombet and Ulrich Weigand.
https://reviews.llvm.org/D19152

llvm-svn: 278927

2 files changed, 24 insertions, 0 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
index 748827c4cfc..6c0ef66dea7 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -20,6 +20,7 @@
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/IR/Intrinsics.h"
 #include <cctype>
 
@@ -531,6 +532,28 @@ bool SystemZTargetLowering::isLegalAddressingMode(const DataLayout &DL,
   return AM.Scale == 0 || AM.Scale == 1;
 }
 
+bool SystemZTargetLowering::isFoldableMemAccessOffset(Instruction *I,
+                                                      int64_t Offset) const {
+  // This only applies to z13.
+  if (!Subtarget.hasVector())
+    return true;
+
+  // * Use LDE instead of LE/LEY to avoid partial register
+  //   dependencies (LDE only supports small offsets).
+  // * Utilize the vector registers to hold floating point
+  //   values (vector load / store instructions only support small
+  //   offsets).
+
+  assert (isa<LoadInst>(I) || isa<StoreInst>(I));
+  Type *MemAccessTy = (isa<LoadInst>(I) ? I->getType() :
+                       I->getOperand(0)->getType());
+  if (!isUInt<12>(Offset) &&
+      (MemAccessTy->isFloatingPointTy() || MemAccessTy->isVectorTy()))
+    return false;
+
+  return true;
+}
+
 bool SystemZTargetLowering::isTruncateFree(Type *FromType, Type *ToType) const {
   if (!FromType->isIntegerTy() || !ToType->isIntegerTy())
     return false;
diff --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.h b/llvm/lib/Target/SystemZ/SystemZISelLowering.h
index b1de8936bee..423b246608c 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.h
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.h
@@ -394,6 +394,7 @@ public:
   bool isLegalAddImmediate(int64_t Imm) const override;
   bool isLegalAddressingMode(const DataLayout &DL, const AddrMode &AM, Type *Ty,
                              unsigned AS) const override;
+  bool isFoldableMemAccessOffset(Instruction *I, int64_t Offset) const override;
   bool allowsMisalignedMemoryAccesses(EVT VT, unsigned AS,
                                       unsigned Align,
                                       bool *Fast) const override;