R600: Implement isTruncateFree

Truncation is just accessing a subregister for any multiple of
the register size, so it's free.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201107 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/R600/AMDGPUISelLowering.cpp b/lib/Target/R600/AMDGPUISelLowering.cpp
index 47f88c3f0c61703502fa92ba9243a9939b3fada4..1df02d3f9873336be6366b5f88fb99da42b429cb 100644 (file)
--- a/lib/Target/R600/AMDGPUISelLowering.cpp
+++ b/lib/Target/R600/AMDGPUISelLowering.cpp
@@ -232,6 +232,11 @@ bool AMDGPUTargetLowering::isFNegFree(EVT VT) const {
   return VT == MVT::f32;
 }
 
+bool AMDGPUTargetLowering::isTruncateFree(EVT, EVT Dest) const {
+  // Truncate is just accessing a subregister.
+  return (Dest.getSizeInBits() % 32 == 0);
+}
+
 //===---------------------------------------------------------------------===//
 // TargetLowering Callbacks
 //===---------------------------------------------------------------------===//

diff --git a/lib/Target/R600/AMDGPUISelLowering.h b/lib/Target/R600/AMDGPUISelLowering.h
index 9782b5e755aef0d9f0600fb06249fa15f3a47548..311959e682ba7e7ad48b388478dc82734080b9d5 100644 (file)
--- a/lib/Target/R600/AMDGPUISelLowering.h
+++ b/lib/Target/R600/AMDGPUISelLowering.h
@@ -81,6 +81,7 @@ public:
 
   virtual bool isFAbsFree(EVT VT) const;
   virtual bool isFNegFree(EVT VT) const;
+  virtual bool isTruncateFree(EVT Src, EVT Dest) const LLVM_OVERRIDE;
   virtual MVT getVectorIdxTy() const;
   virtual bool isLoadBitCastBeneficial(EVT, EVT) const LLVM_OVERRIDE;
   virtual SDValue LowerReturn(SDValue Chain, CallingConv::ID CallConv,