[PATCH] D15286: Utilize direct move instructions for bitcast operations between floating point and integral values

[Nemanja Ivanovic via llvm-commits]

nemanjai created this revision.
nemanjai added reviewers: hfinkel, wschmidt, kbarton, seurer.
nemanjai added a subscriber: llvm-commits.
nemanjai set the repository for this revision to rL LLVM.

LLVM IR frequently contains bitcast operations between floating point and integer values of the same width. Doing this through memory operations is quite expensive on PPC. This patch allows the use of direct register moves between FPRs and GPRs for lowering bitcasts.

Repository:
  rL LLVM

http://reviews.llvm.org/D15286

Files:
  lib/Target/PowerPC/PPCISelLowering.cpp
  lib/Target/PowerPC/PPCInstrVSX.td
  lib/Target/PowerPC/PPCVSXCopy.cpp

Index: lib/Target/PowerPC/PPCVSXCopy.cpp
===================================================================
--- lib/Target/PowerPC/PPCVSXCopy.cpp
+++ lib/Target/PowerPC/PPCVSXCopy.cpp
@@ -81,6 +81,10 @@
       return IsRegInClass(Reg, &PPC::VSFRCRegClass, MRI);
     }
 
+    bool IsVSSReg(unsigned Reg, MachineRegisterInfo &MRI) {
+      return IsRegInClass(Reg, &PPC::VSSRCRegClass, MRI);
+    }
+
 protected:
     bool processBlock(MachineBasicBlock &MBB) {
       bool Changed = false;
@@ -105,6 +109,7 @@
                                            &PPC::VSLRCRegClass;
           assert((IsF8Reg(SrcMO.getReg(), MRI) ||
                   IsVRReg(SrcMO.getReg(), MRI) ||
+                  IsVSSReg(SrcMO.getReg(), MRI) ||
                   IsVSFReg(SrcMO.getReg(), MRI)) &&
                  "Unknown source for a VSX copy");
 
@@ -129,6 +134,7 @@
                                            &PPC::VSLRCRegClass;
           assert((IsF8Reg(DstMO.getReg(), MRI) ||
                   IsVSFReg(DstMO.getReg(), MRI) ||
+                  IsVSSReg(DstMO.getReg(), MRI) ||
                   IsVRReg(DstMO.getReg(), MRI)) &&
                  "Unknown destination for a VSX copy");
 
Index: lib/Target/PowerPC/PPCInstrVSX.td
===================================================================
--- lib/Target/PowerPC/PPCInstrVSX.td
+++ lib/Target/PowerPC/PPCInstrVSX.td
@@ -1631,3 +1631,27 @@
   def : Pat<(i64 (vector_extract v2i64:$S, 1)),
             (i64 MovesFromVSR.LE_DWORD_1)>;
 } // IsLittleEndian, HasDirectMove
+
+let Predicates = [HasDirectMove, HasVSX] in {
+// bitconvert f32 -> i32
+// (convert to 32-bit fp single, shift right 1 word, move to GPR)
+def : Pat<(i32 (bitconvert f32:$S)),
+          (i32 (MFVSRWZ (EXTRACT_SUBREG
+                          (XXSLDWI (XSCVDPSPN $S),(XSCVDPSPN $S), 3),
+                          sub_64)))>;
+// bitconvert i32 -> f32
+// (move to FPR, shift left 1 word, convert to 64-bit fp single)
+def : Pat<(f32 (bitconvert i32:$A)),
+          (f32 (XSCVSPDPN
+                 (XXSLDWI MovesToVSR.LE_WORD_1, MovesToVSR.LE_WORD_1, 1)))>;
+
+// bitconvert f64 -> i64
+// (move to GPR, nothing else needed)
+def : Pat<(i64 (bitconvert f64:$S)),
+          (i64 (MFVSRD $S))>;
+
+// bitconvert i64 -> f64
+// (move to FPR, nothing else needed)
+def : Pat<(f64 (bitconvert i64:$S)),
+          (f64 (MTVSRD $S))>;
+}
Index: lib/Target/PowerPC/PPCISelLowering.cpp
===================================================================
--- lib/Target/PowerPC/PPCISelLowering.cpp
+++ lib/Target/PowerPC/PPCISelLowering.cpp
@@ -257,10 +257,17 @@
   setOperationAction(ISD::SINT_TO_FP, MVT::i32, Expand);
   setOperationAction(ISD::UINT_TO_FP, MVT::i32, Expand);
 
-  setOperationAction(ISD::BITCAST, MVT::f32, Expand);
-  setOperationAction(ISD::BITCAST, MVT::i32, Expand);
-  setOperationAction(ISD::BITCAST, MVT::i64, Expand);
-  setOperationAction(ISD::BITCAST, MVT::f64, Expand);
+  if (Subtarget.hasDirectMove()) {
+    setOperationAction(ISD::BITCAST, MVT::f32, Legal);
+    setOperationAction(ISD::BITCAST, MVT::i32, Legal);
+    setOperationAction(ISD::BITCAST, MVT::i64, Legal);
+    setOperationAction(ISD::BITCAST, MVT::f64, Legal);
+  } else {
+    setOperationAction(ISD::BITCAST, MVT::f32, Expand);
+    setOperationAction(ISD::BITCAST, MVT::i32, Expand);
+    setOperationAction(ISD::BITCAST, MVT::i64, Expand);
+    setOperationAction(ISD::BITCAST, MVT::f64, Expand);
+  }
 
   // We cannot sextinreg(i1).  Expand to shifts.
   setOperationAction(ISD::SIGN_EXTEND_INREG, MVT::i1, Expand);


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