[ARM] MVE i1 splat

We needn't BFI each lane individually into a predicate register when each lane
in the same. A simple sign extend and a vmsr will do.

Differential Revision: https://reviews.llvm.org/D67653

llvm-svn: 372313

Author: davemgreen

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -6945,6 +6945,19 @@ static SDValue LowerBUILD_VECTOR_i1(SDValue Op, SelectionDAG &DAG,
   } else
     return SDValue();
 
+  // If this is a single value copied into all lanes (a splat), we can just sign
+  // extend that single value
+  SDValue FirstOp = Op.getOperand(0);
+  if (!isa<ConstantSDNode>(FirstOp) &&
+      std::all_of(std::next(Op->op_begin()), Op->op_end(),
+                  [&FirstOp](SDUse &U) {
+                    return U.get().isUndef() || U.get() == FirstOp;
+                  })) {
+    SDValue Ext = DAG.getNode(ISD::SIGN_EXTEND_INREG, dl, MVT::i32, FirstOp,
+                              DAG.getValueType(MVT::i1));
+    return DAG.getNode(ARMISD::PREDICATE_CAST, dl, Op.getValueType(), Ext);
+  }
+
   // First create base with bits set where known
   unsigned Bits32 = 0;
   for (unsigned i = 0; i < NumElts; ++i) {
@@ -6957,7 +6970,6 @@ static SDValue LowerBUILD_VECTOR_i1(SDValue Op, SelectionDAG &DAG,
   }
 
   // Add in unknown nodes
-  // FIXME: Handle splats of the same value better.
   SDValue Base = DAG.getNode(ARMISD::PREDICATE_CAST, dl, VT,
                              DAG.getConstant(Bits32, dl, MVT::i32));
   for (unsigned i = 0; i < NumElts; ++i) {

llvm/test/CodeGen/Thumb2/mve-pred-build-var.ll

@@ -44,15 +44,10 @@ define arm_aapcs_vfpcc <4 x i32> @build_varN_v4i1(i32 %s, i32 %t, <4 x i32> %a,
 ; CHECK-LABEL: build_varN_v4i1:
 ; CHECK:       @ %bb.0: @ %entry
 ; CHECK-NEXT:    cmp r0, r1
-; CHECK-NEXT:    mov.w r1, #0
 ; CHECK-NEXT:    cset r0, lo
 ; CHECK-NEXT:    and r0, r0, #1
 ; CHECK-NEXT:    rsbs r0, r0, #0
-; CHECK-NEXT:    bfi r1, r0, #0, #4
-; CHECK-NEXT:    bfi r1, r0, #4, #4
-; CHECK-NEXT:    bfi r1, r0, #8, #4
-; CHECK-NEXT:    bfi r1, r0, #12, #4
-; CHECK-NEXT:    vmsr p0, r1
+; CHECK-NEXT:    vmsr p0, r0
 ; CHECK-NEXT:    vpsel q0, q0, q1
 ; CHECK-NEXT:    bx lr
 entry:
@@ -106,19 +101,10 @@ define arm_aapcs_vfpcc <8 x i16> @build_varN_v8i1(i32 %s, i32 %t, <8 x i16> %a,
 ; CHECK-LABEL: build_varN_v8i1:
 ; CHECK:       @ %bb.0: @ %entry
 ; CHECK-NEXT:    cmp r0, r1
-; CHECK-NEXT:    mov.w r1, #0
 ; CHECK-NEXT:    cset r0, lo
 ; CHECK-NEXT:    and r0, r0, #1
 ; CHECK-NEXT:    rsbs r0, r0, #0
-; CHECK-NEXT:    bfi r1, r0, #0, #2
-; CHECK-NEXT:    bfi r1, r0, #2, #2
-; CHECK-NEXT:    bfi r1, r0, #4, #2
-; CHECK-NEXT:    bfi r1, r0, #6, #2
-; CHECK-NEXT:    bfi r1, r0, #8, #2
-; CHECK-NEXT:    bfi r1, r0, #10, #2
-; CHECK-NEXT:    bfi r1, r0, #12, #2
-; CHECK-NEXT:    bfi r1, r0, #14, #2
-; CHECK-NEXT:    vmsr p0, r1
+; CHECK-NEXT:    vmsr p0, r0
 ; CHECK-NEXT:    vpsel q0, q0, q1
 ; CHECK-NEXT:    bx lr
 entry:
@@ -172,27 +158,10 @@ define arm_aapcs_vfpcc <16 x i8> @build_varN_v16i1(i32 %s, i32 %t, <16 x i8> %a,
 ; CHECK-LABEL: build_varN_v16i1:
 ; CHECK:       @ %bb.0: @ %entry
 ; CHECK-NEXT:    cmp r0, r1
-; CHECK-NEXT:    mov.w r1, #0
 ; CHECK-NEXT:    cset r0, lo
 ; CHECK-NEXT:    and r0, r0, #1
 ; CHECK-NEXT:    rsbs r0, r0, #0
-; CHECK-NEXT:    bfi r1, r0, #0, #1
-; CHECK-NEXT:    bfi r1, r0, #1, #1
-; CHECK-NEXT:    bfi r1, r0, #2, #1
-; CHECK-NEXT:    bfi r1, r0, #3, #1
-; CHECK-NEXT:    bfi r1, r0, #4, #1
-; CHECK-NEXT:    bfi r1, r0, #5, #1
-; CHECK-NEXT:    bfi r1, r0, #6, #1
-; CHECK-NEXT:    bfi r1, r0, #7, #1
-; CHECK-NEXT:    bfi r1, r0, #8, #1
-; CHECK-NEXT:    bfi r1, r0, #9, #1
-; CHECK-NEXT:    bfi r1, r0, #10, #1
-; CHECK-NEXT:    bfi r1, r0, #11, #1
-; CHECK-NEXT:    bfi r1, r0, #12, #1
-; CHECK-NEXT:    bfi r1, r0, #13, #1
-; CHECK-NEXT:    bfi r1, r0, #14, #1
-; CHECK-NEXT:    bfi r1, r0, #15, #1
-; CHECK-NEXT:    vmsr p0, r1
+; CHECK-NEXT:    vmsr p0, r0
 ; CHECK-NEXT:    vpsel q0, q0, q1
 ; CHECK-NEXT:    bx lr
 entry: