Avoid using f64 to lower memcpy from constant string. It's cheaper to use i32 store of immediates.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100751 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 49 insertions, 31 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index afb429edc7..81fc48c8b5 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3210,6 +3210,7 @@ static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
                                      unsigned Limit, uint64_t Size,
                                      unsigned DstAlign, unsigned SrcAlign,
                                      bool NonScalarIntSafe,
+                                     bool MemcpyStrSrc,
                                      SelectionDAG &DAG,
                                      const TargetLowering &TLI) {
   assert((SrcAlign == 0 || SrcAlign >= DstAlign) &&
@@ -3218,9 +3219,11 @@ static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
   // the value, i.e. memset or memcpy from constant string. Otherwise, it's
   // 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.
+  // it's possible to change the alignment of the destination. 'MemcpyStrSrc'
+  // indicates whether the memcpy source is constant so it does not need to be
+  // loaded.
   EVT VT = TLI.getOptimalMemOpType(Size, DstAlign, SrcAlign,
-                                   NonScalarIntSafe, DAG);
+                                   NonScalarIntSafe, MemcpyStrSrc, DAG);
 
   if (VT == MVT::Other) {
     if (DstAlign >= TLI.getTargetData()->getPointerPrefAlignment() ||
@@ -3286,9 +3289,6 @@ static SDValue getMemcpyLoadsAndStores(SelectionDAG &DAG, DebugLoc dl,
   // below a certain threshold.
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   std::vector<EVT> MemOps;
-  uint64_t Limit = -1ULL;
-  if (!AlwaysInline)
-    Limit = TLI.getMaxStoresPerMemcpy();
   bool DstAlignCanChange = false;
   MachineFrameInfo *MFI = DAG.getMachineFunction().getFrameInfo();
   FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Dst);
@@ -3300,9 +3300,13 @@ static SDValue getMemcpyLoadsAndStores(SelectionDAG &DAG, DebugLoc dl,
   std::string Str;
   bool CopyFromStr = isMemSrcFromString(Src, Str);
   bool isZeroStr = CopyFromStr && Str.empty();
+  uint64_t Limit = -1ULL;
+  if (!AlwaysInline)
+    Limit = TLI.getMaxStoresPerMemcpy();
   if (!FindOptimalMemOpLowering(MemOps, Limit, Size,
                                 (DstAlignCanChange ? 0 : Align),
-                                (isZeroStr ? 0 : SrcAlign), true, DAG, TLI))
+                                (isZeroStr ? 0 : SrcAlign),
+                                true, CopyFromStr, DAG, TLI))
     return SDValue();
 
   if (DstAlignCanChange) {
@@ -3390,7 +3394,7 @@ static SDValue getMemmoveLoadsAndStores(SelectionDAG &DAG, DebugLoc dl,
 
   if (!FindOptimalMemOpLowering(MemOps, Limit, Size,
                                 (DstAlignCanChange ? 0 : Align),
-                                SrcAlign, true, DAG, TLI))
+                                SrcAlign, true, false, DAG, TLI))
     return SDValue();
 
   if (DstAlignCanChange) {
@@ -3462,7 +3466,7 @@ static SDValue getMemsetStores(SelectionDAG &DAG, DebugLoc dl,
     isa<ConstantSDNode>(Src) && cast<ConstantSDNode>(Src)->isNullValue();
   if (!FindOptimalMemOpLowering(MemOps, TLI.getMaxStoresPerMemset(),
                                 Size, (DstAlignCanChange ? 0 : Align), 0,
-                                NonScalarIntSafe, DAG, TLI))
+                                NonScalarIntSafe, false, DAG, TLI))
     return SDValue();
 
   if (DstAlignCanChange) {
diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index 9cd01be54e..992cc5a95c 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -5547,11 +5547,14 @@ PPCTargetLowering::isOffsetFoldingLegal(const GlobalAddressSDNode *GA) const {
 /// probably because the source does not need to be loaded. If
 /// 'NonScalarIntSafe' is true, that means it's safe to return a
 /// non-scalar-integer type, e.g. empty string source, constant, or loaded
-/// from memory. It returns EVT::Other if SelectionDAG should be responsible
-/// for determining it.
+/// from memory. 'MemcpyStrSrc' indicates whether the memcpy source is
+/// constant so it does not need to be loaded.
+/// It returns EVT::Other if SelectionDAG should be responsible for
+/// determining the type.
 EVT PPCTargetLowering::getOptimalMemOpType(uint64_t Size,
                                            unsigned DstAlign, unsigned SrcAlign,
                                            bool NonScalarIntSafe,
+                                           bool MemcpyStrSrc,
                                            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 f816bddaf5..f7d629b998 100644
--- a/lib/Target/PowerPC/PPCISelLowering.h
+++ b/lib/Target/PowerPC/PPCISelLowering.h
@@ -355,12 +355,14 @@ namespace llvm {
     /// probably because the source does not need to be loaded. If
     /// 'NonScalarIntSafe' is true, that means it's safe to return a
     /// non-scalar-integer type, e.g. empty string source, constant, or loaded
-    /// from memory. It returns EVT::Other if SelectionDAG should be responsible
-    /// for determining it.
+    /// from memory. 'MemcpyStrSrc' indicates whether the memcpy source is
+    /// constant so it does not need to be loaded.
+    /// It returns EVT::Other if SelectionDAG should be responsible for
+    /// determining the type.
     virtual EVT
-    getOptimalMemOpType(uint64_t Size,
-                        unsigned DstAlign, unsigned SrcAlign,
-                        bool NonScalarIntSafe, SelectionDAG &DAG) const;
+    getOptimalMemOpType(uint64_t Size, unsigned DstAlign, unsigned SrcAlign,
+                        bool NonScalarIntSafe, bool MemcpyStrSrc,
+                        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 678f636b1b..9362d37eae 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1067,18 +1067,22 @@ unsigned X86TargetLowering::getByValTypeAlignment(const Type *Ty) const {
 }
 
 /// getOptimalMemOpType - Returns the target specific optimal type for load
-/// and store operations as a result of memset, memcpy, and memmove lowering.
-/// If DstAlign is zero that means it's safe to destination alignment can
-/// satisfy any constraint. Similarly if SrcAlign is zero it means there
-/// isn't a need to check it against alignment requirement, probably because
-/// the source does not need to be loaded. If 'NonScalarIntSafe' is true, that
-/// means it's safe to return a non-scalar-integer type, e.g. constant string
-/// source or loaded from memory. It returns EVT::Other if SelectionDAG should
-/// be responsible for determining it.
+/// and store operations as a result of memset, memcpy, and memmove
+/// lowering. If DstAlign is zero that means it's safe to destination
+/// alignment can satisfy any constraint. Similarly if SrcAlign is zero it
+/// means there isn't a need to check it against alignment requirement,
+/// probably because the source does not need to be loaded. If
+/// 'NonScalarIntSafe' is true, that means it's safe to return a
+/// non-scalar-integer type, e.g. empty string source, constant, or loaded
+/// from memory. 'MemcpyStrSrc' indicates whether the memcpy source is
+/// constant so it does not need to be loaded.
+/// It returns EVT::Other if SelectionDAG should be responsible for
+/// determining the type.
 EVT
 X86TargetLowering::getOptimalMemOpType(uint64_t Size,
                                        unsigned DstAlign, unsigned SrcAlign,
                                        bool NonScalarIntSafe,
+                                       bool MemcpyStrSrc,
                                        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
@@ -1095,11 +1099,14 @@ X86TargetLowering::getOptimalMemOpType(uint64_t Size,
         return MVT::v4i32;
       if (Subtarget->hasSSE1())
         return MVT::v4f32;
-    } else if (Size >= 8 &&
+    } else if (!MemcpyStrSrc && Size >= 8 &&
                !Subtarget->is64Bit() &&
                Subtarget->getStackAlignment() >= 8 &&
-               Subtarget->hasSSE2())
+               Subtarget->hasSSE2()) {
+      // Do not use f64 to lower memcpy if source is string constant. It's
+      // better to use i32 to avoid the loads.
       return MVT::f64;
+    }
   }
   if (Subtarget->is64Bit() && Size >= 8)
     return MVT::i64;
@@ -6721,7 +6728,7 @@ X86TargetLowering::EmitTargetCodeForMemcpy(SelectionDAG &DAG, DebugLoc dl,
                             Count, InFlag);
   InFlag = Chain.getValue(1);
   Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RDI :
-                                                             X86::EDI,
+                                                              X86::EDI,
                             Dst, InFlag);
   InFlag = Chain.getValue(1);
   Chain  = DAG.getCopyToReg(Chain, dl, Subtarget->is64Bit() ? X86::RSI :
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 1026480ef0..d978676f41 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -424,12 +424,14 @@ namespace llvm {
     /// probably because the source does not need to be loaded. If
     /// 'NonScalarIntSafe' is true, that means it's safe to return a
     /// non-scalar-integer type, e.g. empty string source, constant, or loaded
-    /// from memory. It returns EVT::Other if SelectionDAG should be responsible
-    /// for determining it.
+    /// from memory. 'MemcpyStrSrc' indicates whether the memcpy source is
+    /// constant so it does not need to be loaded.
+    /// It returns EVT::Other if SelectionDAG should be responsible for
+    /// determining the type.
     virtual EVT
-    getOptimalMemOpType(uint64_t Size,
-                        unsigned DstAlign, unsigned SrcAlign,
-                        bool NonScalarIntSafe, SelectionDAG &DAG) const;
+    getOptimalMemOpType(uint64_t Size, unsigned DstAlign, unsigned SrcAlign,
+                        bool NonScalarIntSafe, bool MemcpyStrSrc,
+                        SelectionDAG &DAG) const;
 
     /// allowsUnalignedMemoryAccesses - Returns true if the target allows
     /// unaligned memory accesses. of the specified type.