[mips] Fix inefficient code generation.

This patch eliminates the need to emit a constant move instruction when this
pattern is matched:

(select (setgt a, Constant), T, F)

The pattern above effectively turns into this:

(conditional-move (setlt a, Constant + 1), F, T)

llvm-svn: 176384

3 files changed, 16 insertions, 1 deletions

diff --git a/llvm/lib/Target/Mips/MipsCondMov.td b/llvm/lib/Target/Mips/MipsCondMov.td
index 1c68f2407e4..42e4c99f05d 100644
--- a/llvm/lib/Target/Mips/MipsCondMov.td
+++ b/llvm/lib/Target/Mips/MipsCondMov.td
@@ -68,6 +68,13 @@ multiclass MovzPats0<RegisterClass CRC, RegisterClass DRC,
                 (MOVZInst DRC:$T, (SLTOp CRC:$rhs, CRC:$lhs), DRC:$F)>;
   def : MipsPat<(select (i32 (setule CRC:$lhs, CRC:$rhs)), DRC:$T, DRC:$F),
                 (MOVZInst DRC:$T, (SLTuOp CRC:$rhs, CRC:$lhs), DRC:$F)>;
+  def : MipsPat<(select (i32 (setgt CRC:$lhs, immSExt16Plus1:$rhs)),
+                        DRC:$T, DRC:$F),
+                (MOVZInst DRC:$T, (SLTiOp CRC:$lhs, (Plus1 imm:$rhs)), DRC:$F)>;
+  def : MipsPat<(select (i32 (setugt CRC:$lhs, immSExt16Plus1:$rhs)),
+                        DRC:$T, DRC:$F),
+                (MOVZInst DRC:$T, (SLTiuOp CRC:$lhs, (Plus1 imm:$rhs)),
+                          DRC:$F)>;
 }
 
 multiclass MovzPats1<RegisterClass CRC, RegisterClass DRC,
diff --git a/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp b/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp
index 78c74ef8795..6dff548505b 100644
--- a/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp
+++ b/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp
@@ -109,7 +109,7 @@ private:
        SDValue &Alias);
 
   // getImm - Return a target constant with the specified value.
-  inline SDValue getImm(const SDNode *Node, unsigned Imm) {
+  inline SDValue getImm(const SDNode *Node, uint64_t Imm) {
     return CurDAG->getTargetConstant(Imm, Node->getValueType(0));
   }
 
diff --git a/llvm/lib/Target/Mips/MipsInstrInfo.td b/llvm/lib/Target/Mips/MipsInstrInfo.td
index de09c9ea924..b71ced14936 100644
--- a/llvm/lib/Target/Mips/MipsInstrInfo.td
+++ b/llvm/lib/Target/Mips/MipsInstrInfo.td
@@ -299,6 +299,9 @@ def HI16 : SDNodeXForm<imm, [{
   return getImm(N, (N->getZExtValue() >> 16) & 0xFFFF);
 }]>;
 
+// Plus 1.
+def Plus1 : SDNodeXForm<imm, [{ return getImm(N, N->getSExtValue() + 1); }]>;
+
 // Node immediate fits as 16-bit sign extended on target immediate.
 // e.g. addi, andi
 def immSExt8  : PatLeaf<(imm), [{ return isInt<8>(N->getSExtValue()); }]>;
@@ -331,6 +334,11 @@ def immLow16Zero : PatLeaf<(imm), [{
 // shamt field must fit in 5 bits.
 def immZExt5 : ImmLeaf<i32, [{return Imm == (Imm & 0x1f);}]>;
 
+// True if (N + 1) fits in 16-bit field.
+def immSExt16Plus1 : PatLeaf<(imm), [{
+  return isInt<17>(N->getSExtValue()) && isInt<16>(N->getSExtValue() + 1);
+}]>;
+
 // Mips Address Mode! SDNode frameindex could possibily be a match
 // since load and store instructions from stack used it.
 def addr :