[ARM] Simplify extract of VMOVDRR

Under SoftFP calling conventions, we can be left with
extract(bitcast(BUILD_VECTOR(VMOVDRR(a, b), ..))) patterns that can
simplify to a or b, depending on the extract lane.

Differential Revision: https://reviews.llvm.org/D94990

Author: davemgreen

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -13949,7 +13949,8 @@ static SDValue PerformInsertEltCombine(SDNode *N,
 }
 
 static SDValue PerformExtractEltCombine(SDNode *N,
-                                        TargetLowering::DAGCombinerInfo &DCI) {
+                                        TargetLowering::DAGCombinerInfo &DCI,
+                                        const ARMSubtarget *ST) {
   SDValue Op0 = N->getOperand(0);
   EVT VT = N->getValueType(0);
   SDLoc dl(N);
@@ -13968,6 +13969,19 @@ static SDValue PerformExtractEltCombine(SDNode *N,
       return X;
   }
 
+  // extract(bitcast(BUILD_VECTOR(VMOVDRR(a, b), ..))) -> a or b
+  if (Op0.getValueType() == MVT::v4i32 &&
+      isa<ConstantSDNode>(N->getOperand(1)) &&
+      Op0.getOpcode() == ISD::BITCAST &&
+      Op0.getOperand(0).getOpcode() == ISD::BUILD_VECTOR &&
+      Op0.getOperand(0).getValueType() == MVT::v2f64) {
+    SDValue BV = Op0.getOperand(0);
+    unsigned Offset = N->getConstantOperandVal(1);
+    SDValue MOV = BV.getOperand(Offset < 2 ? 0 : 1);
+    if (MOV.getOpcode() == ARMISD::VMOVDRR)
+      return MOV.getOperand(ST->isLittle() ? Offset % 2 : 1 - Offset % 2);
+  }
+
   return SDValue();
 }
 
@@ -16340,7 +16354,8 @@ SDValue ARMTargetLowering::PerformDAGCombine(SDNode *N,
   case ISD::STORE:      return PerformSTORECombine(N, DCI, Subtarget);
   case ISD::BUILD_VECTOR: return PerformBUILD_VECTORCombine(N, DCI, Subtarget);
   case ISD::INSERT_VECTOR_ELT: return PerformInsertEltCombine(N, DCI);
-  case ISD::EXTRACT_VECTOR_ELT: return PerformExtractEltCombine(N, DCI);
+  case ISD::EXTRACT_VECTOR_ELT:
+    return PerformExtractEltCombine(N, DCI, Subtarget);
   case ISD::VECTOR_SHUFFLE: return PerformVECTOR_SHUFFLECombine(N, DCI.DAG);
   case ARMISD::VDUPLANE: return PerformVDUPLANECombine(N, DCI, Subtarget);
   case ARMISD::VDUP: return PerformVDUPCombine(N, DCI, Subtarget);

llvm/test/CodeGen/Thumb2/mve-soft-float-abi.ll

@@ -95,51 +95,38 @@ define <2 x i64> @vector_add_i64(<2 x i64> %lhs, <2 x i64> %rhs) {
 ; CHECK-MVE:       @ %bb.0: @ %entry
 ; CHECK-MVE-NEXT:    .save {r7, lr}
 ; CHECK-MVE-NEXT:    push {r7, lr}
-; CHECK-MVE-NEXT:    vmov d1, r2, r3
-; CHECK-MVE-NEXT:    add r2, sp, #8
-; CHECK-MVE-NEXT:    vldrw.u32 q1, [r2]
-; CHECK-MVE-NEXT:    vmov d0, r0, r1
-; CHECK-MVE-NEXT:    vmov r1, s2
-; CHECK-MVE-NEXT:    vmov r3, s6
-; CHECK-MVE-NEXT:    vmov r0, s3
-; CHECK-MVE-NEXT:    vmov r2, s7
-; CHECK-MVE-NEXT:    adds.w lr, r1, r3
+; CHECK-MVE-NEXT:    add.w r12, sp, #8
+; CHECK-MVE-NEXT:    vldrw.u32 q0, [r12]
+; CHECK-MVE-NEXT:    vmov lr, s2
+; CHECK-MVE-NEXT:    vmov r12, s3
+; CHECK-MVE-NEXT:    adds.w r2, r2, lr
+; CHECK-MVE-NEXT:    adc.w r12, r12, r3
 ; CHECK-MVE-NEXT:    vmov r3, s0
-; CHECK-MVE-NEXT:    vmov r1, s4
-; CHECK-MVE-NEXT:    adc.w r12, r0, r2
-; CHECK-MVE-NEXT:    vmov r2, s1
-; CHECK-MVE-NEXT:    vmov r0, s5
-; CHECK-MVE-NEXT:    adds r1, r1, r3
-; CHECK-MVE-NEXT:    vmov q0[2], q0[0], r1, lr
-; CHECK-MVE-NEXT:    adcs r0, r2
-; CHECK-MVE-NEXT:    vmov q0[3], q0[1], r0, r12
-; CHECK-MVE-NEXT:    vmov r0, r1, d0
-; CHECK-MVE-NEXT:    vmov r2, r3, d1
+; CHECK-MVE-NEXT:    adds r0, r0, r3
+; CHECK-MVE-NEXT:    vmov q1[2], q1[0], r0, r2
+; CHECK-MVE-NEXT:    vmov r0, s1
+; CHECK-MVE-NEXT:    adcs r0, r1
+; CHECK-MVE-NEXT:    vmov q1[3], q1[1], r0, r12
+; CHECK-MVE-NEXT:    vmov r0, r1, d2
+; CHECK-MVE-NEXT:    vmov r2, r3, d3
 ; CHECK-MVE-NEXT:    pop {r7, pc}
 ;
 ; CHECK-BE-LABEL: vector_add_i64:
 ; CHECK-BE:       @ %bb.0: @ %entry
 ; CHECK-BE-NEXT:    .save {r7, lr}
 ; CHECK-BE-NEXT:    push {r7, lr}
-; CHECK-BE-NEXT:    vmov d1, r3, r2
-; CHECK-BE-NEXT:    add r2, sp, #8
-; CHECK-BE-NEXT:    vmov d0, r1, r0
-; CHECK-BE-NEXT:    vrev64.32 q1, q0
-; CHECK-BE-NEXT:    vldrw.u32 q0, [r2]
-; CHECK-BE-NEXT:    vmov r1, s7
-; CHECK-BE-NEXT:    vmov r3, s3
-; CHECK-BE-NEXT:    vmov r0, s6
-; CHECK-BE-NEXT:    vmov r2, s2
-; CHECK-BE-NEXT:    adds.w r12, r1, r3
-; CHECK-BE-NEXT:    vmov r3, s5
-; CHECK-BE-NEXT:    vmov r1, s0
-; CHECK-BE-NEXT:    adc.w lr, r0, r2
-; CHECK-BE-NEXT:    vmov r0, s1
-; CHECK-BE-NEXT:    vmov r2, s4
-; CHECK-BE-NEXT:    adds r0, r0, r3
-; CHECK-BE-NEXT:    adcs r1, r2
-; CHECK-BE-NEXT:    vmov q0[2], q0[0], r1, lr
-; CHECK-BE-NEXT:    vmov q0[3], q0[1], r0, r12
+; CHECK-BE-NEXT:    add.w r12, sp, #8
+; CHECK-BE-NEXT:    vldrw.u32 q0, [r12]
+; CHECK-BE-NEXT:    vmov lr, s3
+; CHECK-BE-NEXT:    vmov r12, s2
+; CHECK-BE-NEXT:    adds.w lr, lr, r3
+; CHECK-BE-NEXT:    vmov r3, s0
+; CHECK-BE-NEXT:    adc.w r12, r12, r2
+; CHECK-BE-NEXT:    vmov r2, s1
+; CHECK-BE-NEXT:    adds r1, r1, r2
+; CHECK-BE-NEXT:    adcs r0, r3
+; CHECK-BE-NEXT:    vmov q0[2], q0[0], r0, r12
+; CHECK-BE-NEXT:    vmov q0[3], q0[1], r1, lr
 ; CHECK-BE-NEXT:    vrev64.32 q1, q0
 ; CHECK-BE-NEXT:    vmov r1, r0, d2
 ; CHECK-BE-NEXT:    vmov r3, r2, d3
@@ -149,24 +136,18 @@ define <2 x i64> @vector_add_i64(<2 x i64> %lhs, <2 x i64> %rhs) {
 ; CHECK-FP:       @ %bb.0: @ %entry
 ; CHECK-FP-NEXT:    .save {r7, lr}
 ; CHECK-FP-NEXT:    push {r7, lr}
-; CHECK-FP-NEXT:    vmov d1, r2, r3
-; CHECK-FP-NEXT:    vmov d0, r0, r1
-; CHECK-FP-NEXT:    add r0, sp, #8
-; CHECK-FP-NEXT:    vldrw.u32 q1, [r0]
-; CHECK-FP-NEXT:    vmov r1, s2
-; CHECK-FP-NEXT:    vmov r0, s3
-; CHECK-FP-NEXT:    vmov r3, s6
-; CHECK-FP-NEXT:    vmov r2, s7
-; CHECK-FP-NEXT:    adds.w lr, r1, r3
-; CHECK-FP-NEXT:    vmov r3, s0
-; CHECK-FP-NEXT:    vmov r1, s4
-; CHECK-FP-NEXT:    adc.w r12, r0, r2
-; CHECK-FP-NEXT:    vmov r2, s1
-; CHECK-FP-NEXT:    vmov r0, s5
-; CHECK-FP-NEXT:    adds r1, r1, r3
-; CHECK-FP-NEXT:    vmov q0[2], q0[0], r1, lr
-; CHECK-FP-NEXT:    adcs r0, r2
-; CHECK-FP-NEXT:    vmov q0[3], q0[1], r0, r12
+; CHECK-FP-NEXT:    add.w r12, sp, #8
+; CHECK-FP-NEXT:    vldrw.u32 q0, [r12]
+; CHECK-FP-NEXT:    vmov lr, s2
+; CHECK-FP-NEXT:    vmov r12, s3
+; CHECK-FP-NEXT:    adds.w lr, lr, r2
+; CHECK-FP-NEXT:    vmov r2, s0
+; CHECK-FP-NEXT:    adc.w r12, r12, r3
+; CHECK-FP-NEXT:    vmov r3, s1
+; CHECK-FP-NEXT:    adds r0, r0, r2
+; CHECK-FP-NEXT:    adcs r1, r3
+; CHECK-FP-NEXT:    vmov q0[2], q0[0], r0, lr
+; CHECK-FP-NEXT:    vmov q0[3], q0[1], r1, r12
 ; CHECK-FP-NEXT:    vmov r0, r1, d0
 ; CHECK-FP-NEXT:    vmov r2, r3, d1
 ; CHECK-FP-NEXT:    pop {r7, pc}