Reapply [FastISel][X86] Emit more efficient instructions for integer constant materialization (r215593).

Note: This was originally reverted to track down a buildbot error. Reapply
without any modifications.

Original commit message:
This mostly affects the i64 value type, which always resulted in an 15byte
mobavsq instruction to materialize any constant. The custom code checks the
value of the immediate and tries to use a different and smaller mov
instruction when possible.

This fixes <rdar://problem/17420988>.

llvm-svn: 216010

1 files changed, 28 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86FastISel.cpp b/llvm/lib/Target/X86/X86FastISel.cpp
index 2166b8a057c..6426d27ae1a 100644
--- a/llvm/lib/Target/X86/X86FastISel.cpp
+++ b/llvm/lib/Target/X86/X86FastISel.cpp
@@ -3105,7 +3105,34 @@ X86FastISel::TargetSelectInstruction(const Instruction *I)  {
 unsigned X86FastISel::X86MaterializeInt(const ConstantInt *CI, MVT VT) {
   if (VT > MVT::i64)
     return 0;
-  return FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
+
+  uint64_t Imm = CI->getZExtValue();
+  unsigned Opc = 0;
+  switch (VT.SimpleTy) {
+  default: llvm_unreachable("Unexpected value type");
+  case MVT::i1:  VT = MVT::i8; // fall-through
+  case MVT::i8:  Opc = X86::MOV8ri;  break;
+  case MVT::i16: Opc = X86::MOV16ri; break;
+  case MVT::i32: Opc = X86::MOV32ri; break;
+  case MVT::i64: {
+    if (isUInt<32>(Imm))
+      Opc = X86::MOV32ri;
+    else if (isInt<32>(Imm))
+      Opc = X86::MOV64ri32;
+    else
+      Opc = X86::MOV64ri;
+    break;
+  }
+  }
+  if (VT == MVT::i64 && Opc == X86::MOV32ri) {
+    unsigned SrcReg = FastEmitInst_i(Opc, &X86::GR32RegClass, Imm);
+    unsigned ResultReg = createResultReg(&X86::GR64RegClass);
+    BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
+            TII.get(TargetOpcode::SUBREG_TO_REG), ResultReg)
+      .addImm(0).addReg(SrcReg).addImm(X86::sub_32bit);
+    return ResultReg;
+  }
+  return FastEmitInst_i(Opc, TLI.getRegClassFor(VT), Imm);
 }
 
 unsigned X86FastISel::X86MaterializeFP(const ConstantFP *CFP, MVT VT) {