[PATCH] D20667: ARM: Add additional matching for UBFX instructions.

[Dave Green via llvm-commits]

dmgreen created this revision.
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dmgreen set the repository for this revision to rL LLVM.
Herald added subscribers: rengolin, aemerson.

This adds an additional matcher to select UBFX(..) from SRL(AND(..)) in ARMISelDAGToDAG to help with code size.

Repository:
  rL LLVM

http://reviews.llvm.org/D20667

Files:
  lib/Target/ARM/ARMISelDAGToDAG.cpp
  test/CodeGen/ARM/bfx.ll

Index: test/CodeGen/ARM/bfx.ll
===================================================================
--- test/CodeGen/ARM/bfx.ll
+++ test/CodeGen/ARM/bfx.ll
@@ -51,3 +51,19 @@
   %add7 = add i32 %add, %2
   ret i32 %add7
 }
+
+define i32 @ubfx3(i32 %a) {
+; CHECK: ubfx3
+; CHECK: ubfx r0, r0, #11, #1
+	%t1 = and i32 %a, 2048
+	%t2 = lshr i32 %t1, 11
+	ret i32 %t2
+}
+
+define i32 @ubfx4(i32 %a) {
+; CHECK: ubfx4
+; CHECK: ubfx r0, r0, #7, #3
+	%t1 = and i32 %a, 896
+	%t2 = lshr i32 %t1, 7
+	ret i32 %t2
+}
Index: lib/Target/ARM/ARMISelDAGToDAG.cpp
===================================================================
--- lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -2416,6 +2416,27 @@
     }
   }
 
+  // Or we are looking for a shift of an and, with a mask operand
+  if (isOpcWithIntImmediate(N->getOperand(0).getNode(), ISD::AND, And_imm) &&
+      isShiftedMask_32(And_imm)) {
+    unsigned Srl_imm = 0;
+    unsigned LSB = countTrailingZeros(And_imm);
+    // Shift must be the same as the ands lsb
+    if (isInt32Immediate(N->getOperand(1), Srl_imm) && Srl_imm == LSB) {
+      assert(Srl_imm > 0 && Srl_imm < 32 && "bad amount in shift node!");
+      unsigned MSB = 31 - countLeadingZeros(And_imm);
+      // Note: The width operand is encoded as width-1.
+      unsigned Width = MSB - LSB;
+      SDValue Reg0 = CurDAG->getRegister(0, MVT::i32);
+      SDValue Ops[] = { N->getOperand(0).getOperand(0),
+                        CurDAG->getTargetConstant(Srl_imm, dl, MVT::i32),
+                        CurDAG->getTargetConstant(Width, dl, MVT::i32),
+                        getAL(CurDAG, dl), Reg0 };
+      CurDAG->SelectNodeTo(N, Opc, MVT::i32, Ops);
+      return true;
+    }
+  }
+
   if (N->getOpcode() == ISD::SIGN_EXTEND_INREG) {
     unsigned Width = cast<VTSDNode>(N->getOperand(1))->getVT().getSizeInBits();
     unsigned LSB = 0;


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