- Avoid using floating point stores to implement memset unless the value is zero.

- Do not try to infer GV alignment unless its type is sized. It's not possible to infer alignment if it has opaque type.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100118 91177308-0d34-0410-b5e6-96231b3b80d8

7 files changed, 32 insertions, 17 deletions

diff --git a/include/llvm/Target/TargetLowering.h b/include/llvm/Target/TargetLowering.h
index 23506c9..ad6fcef 100644
--- a/include/llvm/Target/TargetLowering.h
+++ b/include/llvm/Target/TargetLowering.h
@@ -638,7 +638,7 @@ public:
   /// determining it.
   virtual EVT getOptimalMemOpType(uint64_t Size,
                                   unsigned DstAlign, unsigned SrcAlign,
-                                  SelectionDAG &DAG) const {
+                                  bool SafeToUseFP, SelectionDAG &DAG) const {
     return MVT::Other;
   }
   
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 25bf861..4fcfeec 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3195,9 +3195,9 @@ static bool isMemSrcFromString(SDValue Src, std::string &Str) {
 /// is below the threshold. It returns the types of the sequence of
 /// memory ops to perform memset / memcpy by reference.
 static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
-                                     SDValue Dst, SDValue Src,
                                      unsigned Limit, uint64_t Size,
                                      unsigned DstAlign, unsigned SrcAlign,
+                                     bool SafeToUseFP,
                                      SelectionDAG &DAG,
                                      const TargetLowering &TLI) {
   assert((SrcAlign == 0 || SrcAlign >= DstAlign) &&
@@ -3207,7 +3207,7 @@ static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
   // the inferred alignment of the source. 'DstAlign', on the other hand, is the
   // specified alignment of the memory operation. If it is zero, that means
   // it's possible to change the alignment of the destination.
-  EVT VT = TLI.getOptimalMemOpType(Size, DstAlign, SrcAlign, DAG);
+  EVT VT = TLI.getOptimalMemOpType(Size, DstAlign, SrcAlign, SafeToUseFP, DAG);
 
   if (VT == MVT::Other) {
     VT = TLI.getPointerTy();
@@ -3285,9 +3285,9 @@ static SDValue getMemcpyLoadsAndStores(SelectionDAG &DAG, DebugLoc dl,
   std::string Str;
   bool CopyFromStr = isMemSrcFromString(Src, Str);
   bool isZeroStr = CopyFromStr && Str.empty();
-  if (!FindOptimalMemOpLowering(MemOps, Dst, Src, Limit, Size,
+  if (!FindOptimalMemOpLowering(MemOps, Limit, Size,
                                 (DstAlignCanChange ? 0 : Align),
-                                (isZeroStr ? 0 : SrcAlign), DAG, TLI))
+                                (isZeroStr ? 0 : SrcAlign), true, DAG, TLI))
     return SDValue();
 
   if (DstAlignCanChange) {
@@ -3369,9 +3369,9 @@ static SDValue getMemmoveLoadsAndStores(SelectionDAG &DAG, DebugLoc dl,
   if (Align > SrcAlign)
     SrcAlign = Align;
 
-  if (!FindOptimalMemOpLowering(MemOps, Dst, Src, Limit, Size,
+  if (!FindOptimalMemOpLowering(MemOps, Limit, Size,
                                 (DstAlignCanChange ? 0 : Align),
-                                SrcAlign, DAG, TLI))
+                                SrcAlign, true, DAG, TLI))
     return SDValue();
 
   if (DstAlignCanChange) {
@@ -3436,9 +3436,11 @@ static SDValue getMemsetStores(SelectionDAG &DAG, DebugLoc dl,
   FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Dst);
   if (FI && !MFI->isFixedObjectIndex(FI->getIndex()))
     DstAlignCanChange = true;
-  if (!FindOptimalMemOpLowering(MemOps, Dst, Src, TLI.getMaxStoresPerMemset(),
+  bool IsZero = isa<ConstantSDNode>(Src) &&
+    cast<ConstantSDNode>(Src)->isNullValue();
+  if (!FindOptimalMemOpLowering(MemOps, TLI.getMaxStoresPerMemset(),
                                 Size, (DstAlignCanChange ? 0 : Align), 0,
-                                DAG, TLI))
+                                IsZero, DAG, TLI))
     return SDValue();
 
   if (DstAlignCanChange) {
@@ -6150,8 +6152,10 @@ unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) const {
     unsigned Align = GV->getAlignment();
     if (!Align) {
       if (GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
-        const TargetData *TD = TLI.getTargetData();
-        Align = TD->getPreferredAlignment(GVar);
+        if (GV->getType()->getElementType()->isSized()) {
+          const TargetData *TD = TLI.getTargetData();
+          Align = TD->getPreferredAlignment(GVar);
+        }
       }
     }
     return MinAlign(Align, GVOffset);
diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index d00fbff..d043ec6 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -5541,6 +5541,7 @@ PPCTargetLowering::isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const {
 
 EVT PPCTargetLowering::getOptimalMemOpType(uint64_t Size,
                                            unsigned DstAlign, unsigned SrcAlign,
+                                           bool SafeToUseFP,
                                            SelectionDAG &DAG) const {
   if (this->PPCSubTarget.isPPC64()) {
     return MVT::i64;
diff --git a/lib/Target/PowerPC/PPCISelLowering.h b/lib/Target/PowerPC/PPCISelLowering.h
index 2d5daef..bb2d84e 100644
--- a/lib/Target/PowerPC/PPCISelLowering.h
+++ b/lib/Target/PowerPC/PPCISelLowering.h
@@ -349,7 +349,7 @@ namespace llvm {
     
     virtual EVT getOptimalMemOpType(uint64_t Size,
                                     unsigned DstAlign, unsigned SrcAlign,
-                                    SelectionDAG &DAG) const;
+                                    bool SafeToUseFP, SelectionDAG &DAG) const;
 
     /// getFunctionAlignment - Return the Log2 alignment of this function.
     virtual unsigned getFunctionAlignment(const Function *F) const;
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index bd268ec..5d6e571 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1076,6 +1076,7 @@ unsigned X86TargetLowering::getByValTypeAlignment(const Type *Ty) const {
 EVT
 X86TargetLowering::getOptimalMemOpType(uint64_t Size,
                                        unsigned DstAlign, unsigned SrcAlign,
+                                       bool SafeToUseFP,
                                        SelectionDAG &DAG) const {
   // FIXME: This turns off use of xmm stores for memset/memcpy on targets like
   // linux.  This is because the stack realignment code can't handle certain
@@ -1089,9 +1090,10 @@ X86TargetLowering::getOptimalMemOpType(uint64_t Size,
         Subtarget->getStackAlignment() >= 16) {
       if (Subtarget->hasSSE2())
         return MVT::v4i32;
-      if (Subtarget->hasSSE1())
+      if (SafeToUseFP && Subtarget->hasSSE1())
         return MVT::v4f32;
-    } else if (Size >= 8 &&
+    } else if (SafeToUseFP &&
+               Size >= 8 &&
                Subtarget->getStackAlignment() >= 8 &&
                Subtarget->hasSSE2())
       return MVT::f64;
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 569dc1f..cc7e964 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -425,7 +425,7 @@ namespace llvm {
     /// determining it.
     virtual EVT getOptimalMemOpType(uint64_t Size,
                                     unsigned DstAlign, unsigned SrcAlign,
-                                    SelectionDAG &DAG) const;
+                                    bool SafeToUseFP, SelectionDAG &DAG) const;
 
     /// allowsUnalignedMemoryAccesses - Returns true if the target allows
     /// unaligned memory accesses. of the specified type.
diff --git a/test/CodeGen/X86/memset-2.ll b/test/CodeGen/X86/memset-2.ll
index e2eba76..702632c 100644
--- a/test/CodeGen/X86/memset-2.ll
+++ b/test/CodeGen/X86/memset-2.ll
@@ -4,10 +4,18 @@ target triple = "i386"
 
 declare void @llvm.memset.i32(i8*, i8, i32, i32) nounwind
 
-define fastcc void @t() nounwind {
+define fastcc void @t1() nounwind {
 entry:
-; CHECK: t:
+; CHECK: t1:
 ; CHECK: call memset
   call void @llvm.memset.i32( i8* null, i8 0, i32 188, i32 1 ) nounwind
   unreachable
 }
+
+define fastcc void @t2(i8 signext %c) nounwind {
+entry:
+; CHECK: t2:
+; CHECK: call memset
+  call void @llvm.memset.i32( i8* undef, i8 %c, i32 76, i32 1 ) nounwind
+  unreachable
+}