ARM Cost Model: Modify the target independent cost model to ask

the target if it supports the different CAST types. We didn't do this
on X86 because of the different register sizes and types, but on ARM
this makes sense.

llvm-svn: 172245

1 files changed, 21 insertions, 12 deletions

diff --git a/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp b/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
index 3892cc4dd55..59192f444e5 100644
--- a/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
+++ b/llvm/lib/CodeGen/BasicTargetTransformInfo.cpp
@@ -241,6 +241,27 @@ unsigned BasicTTI::getCastInstrCost(unsigned Opcode, Type *Dst,
   std::pair<unsigned, MVT> SrcLT = TLI->getTypeLegalizationCost(Src);
   std::pair<unsigned, MVT> DstLT = TLI->getTypeLegalizationCost(Dst);
 
+  // Check for NOOP conversions.
+  if (SrcLT.first == DstLT.first &&
+      SrcLT.second.getSizeInBits() == DstLT.second.getSizeInBits()) {
+
+      // Bitcast between types that are legalized to the same type are free.
+      if (Opcode == Instruction::BitCast || Opcode == Instruction::Trunc)
+        return 0;
+  }
+
+  if (Opcode == Instruction::Trunc &&
+      TLI->isTruncateFree(SrcLT.second, DstLT.second))
+    return 0;
+
+  if (Opcode == Instruction::ZExt &&
+      TLI->isZExtFree(SrcLT.second, DstLT.second))
+    return 0;
+
+  // If the cast is marked as legal (or promote) then assume low cost.
+  if (TLI->isOperationLegalOrPromote(ISD, DstLT.second))
+    return 1;
+
   // Handle scalar conversions.
   if (!Src->isVectorTy() && !Dst->isVectorTy()) {
 
@@ -248,14 +269,6 @@ unsigned BasicTTI::getCastInstrCost(unsigned Opcode, Type *Dst,
     if (Opcode == Instruction::BitCast)
       return 0;
 
-    if (Opcode == Instruction::Trunc &&
-        TLI->isTruncateFree(SrcLT.second, DstLT.second))
-      return 0;
-
-    if (Opcode == Instruction::ZExt &&
-        TLI->isZExtFree(SrcLT.second, DstLT.second))
-      return 0;
-
     // Just check the op cost. If the operation is legal then assume it costs 1.
     if (!TLI->isOperationExpand(ISD, DstLT.second))
       return  1;
@@ -271,10 +284,6 @@ unsigned BasicTTI::getCastInstrCost(unsigned Opcode, Type *Dst,
     if (SrcLT.first == DstLT.first &&
         SrcLT.second.getSizeInBits() == DstLT.second.getSizeInBits()) {
 
-      // Bitcast between types that are legalized to the same type are free.
-      if (Opcode == Instruction::BitCast || Opcode == Instruction::Trunc)
-        return 0;
-
       // Assume that Zext is done using AND.
       if (Opcode == Instruction::ZExt)
         return 1;