Avoid using lossy load / stores for memcpy / memset expansion. e.g.

f64 load / store on non-SSE2 x86 targets.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169944 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetLowering.h

@@ -716,6 +716,15 @@ public:
     return MVT::Other;
   }
 
+  /// isLegalMemOpType - Returns true if it's legal to use load / store of the
+  /// specified type to expand memcpy / memset inline. This is mostly true
+  /// for legal types except for some special cases. For example, on X86
+  /// targets without SSE2 f64 load / store are done with fldl / fstpl which
+  /// also does type conversion.
+  virtual bool isLegalMemOpType(MVT VT) const {
+    return VT.isInteger();
+  }
+
   /// usesUnderscoreSetJmp - Determine if we should use _setjmp or setjmp
   /// to implement llvm.setjmp.
   bool usesUnderscoreSetJmp() const {

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -3474,27 +3474,33 @@ static bool FindOptimalMemOpLowering(std::vector<EVT> &MemOps,
     unsigned VTSize = VT.getSizeInBits() / 8;
     while (VTSize > Size) {
       // For now, only use non-vector load / store's for the left-over pieces.
-      EVT NewVT;
+      EVT NewVT = VT;
       unsigned NewVTSize;
+
+      bool Found = false;
       if (VT.isVector() || VT.isFloatingPoint()) {
         NewVT = (VT.getSizeInBits() > 64) ? MVT::i64 : MVT::i32;
-        while (!TLI.isOperationLegalOrCustom(ISD::STORE, NewVT)) {
-          if (NewVT == MVT::i64 &&
-              TLI.isOperationLegalOrCustom(ISD::STORE, MVT::f64)) {
-            // i64 is usually not legal on 32-bit targets, but f64 may be.
-            NewVT = MVT::f64;
-            break;
-          }
-          NewVT = (MVT::SimpleValueType)(NewVT.getSimpleVT().SimpleTy - 1);
+        if (TLI.isOperationLegalOrCustom(ISD::STORE, NewVT) &&
+            TLI.isLegalMemOpType(NewVT.getSimpleVT()))
+          Found = true;
+        else if (NewVT == MVT::i64 &&
+                 TLI.isOperationLegalOrCustom(ISD::STORE, MVT::f64) &&
+                 TLI.isLegalMemOpType(MVT::f64)) {
+          // i64 is usually not legal on 32-bit targets, but f64 may be.
+          NewVT = MVT::f64;
+          Found = true;
         }
-        NewVTSize = NewVT.getSizeInBits() / 8;
-      } else {
-        // This can result in a type that is not legal on the target, e.g.
-        // 1 or 2 bytes on PPC.
-        NewVT = (MVT::SimpleValueType)(VT.getSimpleVT().SimpleTy - 1);
-        NewVTSize = VTSize >> 1;
       }
 
+      if (!Found) {
+        do {
+          NewVT = (MVT::SimpleValueType)(NewVT.getSimpleVT().SimpleTy - 1);
+          if (NewVT == MVT::i8)
+            break;
+        } while (!TLI.isLegalMemOpType(NewVT.getSimpleVT()));
+      }
+      NewVTSize = NewVT.getSizeInBits() / 8;
+
       // If the new VT cannot cover all of the remaining bits, then consider
       // issuing a (or a pair of) unaligned and overlapping load / store.
       // FIXME: Only does this for 64-bit or more since we don't have proper

lib/Target/ARM/ARMISelLowering.cpp

@@ -9481,6 +9481,10 @@ EVT ARMTargetLowering::getOptimalMemOpType(uint64_t Size,
   return MVT::Other;
 }
 
+bool ARMTargetLowering::isLegalMemOpType(MVT VT) const {
+  return VT.isInteger() || VT == MVT::f64 || VT == MVT::v2f64;
+}
+
 bool ARMTargetLowering::isZExtFree(SDValue Val, EVT VT2) const {
   if (Val.getOpcode() != ISD::LOAD)
     return false;

lib/Target/ARM/ARMISelLowering.h

@@ -296,6 +296,13 @@ namespace llvm {
                                     bool MemcpyStrSrc,
                                     MachineFunction &MF) const;
 
+    /// isLegalMemOpType - Returns true if it's legal to use load / store of the
+    /// specified type to expand memcpy / memset inline. This is mostly true
+    /// for legal types except for some special cases. For example, on X86
+    /// targets without SSE2 f64 load / store are done with fldl / fstpl which
+    /// also does type conversion.
+    virtual bool isLegalMemOpType(MVT VT) const;
+
     using TargetLowering::isZExtFree;
     virtual bool isZExtFree(SDValue Val, EVT VT2) const;
 

lib/Target/X86/X86ISelLowering.cpp

@@ -1412,6 +1412,14 @@ X86TargetLowering::getOptimalMemOpType(uint64_t Size,
   return MVT::i32;
 }
 
+bool X86TargetLowering::isLegalMemOpType(MVT VT) const {
+  if (VT == MVT::f32)
+    return X86ScalarSSEf32;
+  else if (VT == MVT::f64)
+    return X86ScalarSSEf64;
+  return VT.isInteger();
+}
+
 bool
 X86TargetLowering::allowsUnalignedMemoryAccesses(EVT VT, bool *Fast) const {
   if (Fast)

lib/Target/X86/X86ISelLowering.h

@@ -506,6 +506,13 @@ namespace llvm {
                         bool IsZeroVal, bool MemcpyStrSrc,
                         MachineFunction &MF) const;
 
+    /// isLegalMemOpType - Returns true if it's legal to use load / store of the
+    /// specified type to expand memcpy / memset inline. This is mostly true
+    /// for legal types except for some special cases. For example, on X86
+    /// targets without SSE2 f64 load / store are done with fldl / fstpl which
+    /// also does type conversion.
+    virtual bool isLegalMemOpType(MVT VT) const;
+
     /// allowsUnalignedMemoryAccesses - Returns true if the target allows
     /// unaligned memory accesses. of the specified type. Returns whether it
     /// is "fast" by reference in the second argument.

test/CodeGen/X86/memcpy-2.ll

@@ -17,11 +17,11 @@ entry:
 ; SSE2: movb $0, 24(%esp)
 
 ; SSE1: t1:
-; SSE1: fldl _.str+16
-; SSE1: fstpl 16(%esp)
 ; SSE1: movaps _.str, %xmm0
 ; SSE1: movaps %xmm0
 ; SSE1: movb $0, 24(%esp)
+; SSE1: movl $0, 20(%esp)
+; SSE1: movl $0, 16(%esp)
 
 ; NOSSE: t1:
 ; NOSSE: movb $0