[VPlan] Use EMIT-SCALAR for single-scalar VPPhis (NFC).

Follow-up to #141428, to also
use EMIT-SCALAR for VPPhis that are single scalars.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -1111,7 +1111,7 @@ void VPPhi::execute(VPTransformState &State) {
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void VPPhi::print(raw_ostream &O, const Twine &Indent,
                   VPSlotTracker &SlotTracker) const {
-  O << Indent << "EMIT ";
+  O << Indent << "EMIT" << (isSingleScalar() ? "-SCALAR" : "") << " ";
   printAsOperand(O, SlotTracker);
   O << " = phi ";
 

llvm/test/Transforms/LoopVectorize/AArch64/vplan-printing.ll

@@ -86,7 +86,7 @@ define i32 @print_partial_reduction(ptr %a, ptr %b) {
 ; CHECK-NEXT: Successor(s): vector.body
 ; CHECK-EMPTY:
 ; CHECK-NEXT: vector.body:
-; CHECK-NEXT:   EMIT vp<[[EP_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<%index.next>, vector.body ]
+; CHECK-NEXT:   EMIT-SCALAR vp<[[EP_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<%index.next>, vector.body ]
 ; CHECK-NEXT:   WIDEN-REDUCTION-PHI ir<%accum> = phi ir<0>, ir<%add> (VF scaled by 1/4)
 ; CHECK-NEXT:   CLONE ir<%gep.a> = getelementptr ir<%a>, vp<[[EP_IV]]>
 ; CHECK-NEXT:   vp<[[PTR_A:%.+]]> = vector-pointer ir<%gep.a>

llvm/test/Transforms/LoopVectorize/RISCV/riscv-vector-reverse.ll

@@ -196,7 +196,7 @@ define void @vector_reverse_i64(ptr nocapture noundef writeonly %A, ptr nocaptur
 ; CHECK-NEXT:  Successor(s): vector.body
 ; CHECK-EMPTY:
 ; CHECK-NEXT:  vector.body:
-; CHECK-NEXT:    EMIT vp<[[CAN_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[CAN_IV_NEXT:%.+]]>, vector.body ]
+; CHECK-NEXT:    EMIT-SCALAR vp<[[CAN_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[CAN_IV_NEXT:%.+]]>, vector.body ]
 ; CHECK-NEXT:    vp<[[DEV_IV:%.+]]> = DERIVED-IV ir<%n> + vp<[[CAN_IV]]> * ir<-1>
 ; CHECK-NEXT:    CLONE ir<%i.0> = add nsw vp<[[DEV_IV]]>, ir<-1>
 ; CHECK-NEXT:    CLONE ir<%idxprom> = zext ir<%i.0>
@@ -444,7 +444,7 @@ define void @vector_reverse_f32(ptr nocapture noundef writeonly %A, ptr nocaptur
 ; CHECK-NEXT:  Successor(s): vector.body
 ; CHECK-EMPTY:
 ; CHECK-NEXT:  vector.body:
-; CHECK-NEXT:    EMIT vp<[[CAN_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[CAN_IV_NEXT:%.+]]>, vector.body ]
+; CHECK-NEXT:    EMIT-SCALAR vp<[[CAN_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[CAN_IV_NEXT:%.+]]>, vector.body ]
 ; CHECK-NEXT:    vp<[[DEV_IV:%.+]]> = DERIVED-IV ir<%n> + vp<[[CAN_IV]]> * ir<-1>
 ; CHECK-NEXT:    CLONE ir<%i.0> = add nsw vp<[[DEV_IV]]>, ir<-1>
 ; CHECK-NEXT:    CLONE ir<%idxprom> = zext ir<%i.0>

llvm/test/Transforms/LoopVectorize/RISCV/vplan-vp-intrinsics-fixed-order-recurrence.ll

@@ -27,7 +27,7 @@ define void @first_order_recurrence(ptr noalias %A, ptr noalias %B, i64 %TC) {
 ; IF-EVL-NEXT:     EMIT vp<[[IV:%[0-9]+]]> = CANONICAL-INDUCTION
 ; IF-EVL-NEXT:     EXPLICIT-VECTOR-LENGTH-BASED-IV-PHI vp<[[EVL_PHI:%[0-9]+]]> = phi ir<0>, vp<[[IV_NEXT:%.+]]>
 ; IF-EVL-NEXT:     FIRST-ORDER-RECURRENCE-PHI ir<[[FOR_PHI:%.+]]> = phi ir<33>, ir<[[LD:%.+]]>
-; IF-EVL-NEXT:     EMIT vp<[[PREV_EVL:%.+]]> = phi [ vp<[[VF32]]>, vector.ph ], [ vp<[[EVL:%.+]]>, vector.body ]
+; IF-EVL-NEXT:     EMIT-SCALAR vp<[[PREV_EVL:%.+]]> = phi [ vp<[[VF32]]>, vector.ph ], [ vp<[[EVL:%.+]]>, vector.body ]
 ; IF-EVL-NEXT:     EMIT vp<[[AVL:%.+]]> = sub ir<%TC>, vp<[[EVL_PHI]]>
 ; IF-EVL-NEXT:     EMIT vp<[[EVL]]> = EXPLICIT-VECTOR-LENGTH vp<[[AVL]]>
 ; IF-EVL-NEXT:     vp<[[ST:%[0-9]+]]> = SCALAR-STEPS vp<[[EVL_PHI]]>, ir<1>

llvm/test/Transforms/LoopVectorize/RISCV/vplan-vp-select-intrinsics.ll

@@ -31,8 +31,8 @@
  ; IF-EVL-NEXT: Successor(s): vector.body
  ; IF-EVL-EMPTY:
  ; IF-EVL-NEXT: vector.body:
- ; IF-EVL-NEXT:   EMIT vp<[[IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[IV_NEXT_EXIT:%.+]]>, vector.body ]
- ; IF-EVL-NEXT:   EMIT vp<[[EVL_PHI:%.+]]>  = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[IV_NEX:%.+]]>, vector.body ]
+ ; IF-EVL-NEXT:   EMIT-SCALAR vp<[[IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[IV_NEXT_EXIT:%.+]]>, vector.body ]
+ ; IF-EVL-NEXT:   EMIT-SCALAR vp<[[EVL_PHI:%.+]]>  = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[IV_NEX:%.+]]>, vector.body ]
  ; IF-EVL-NEXT:   EMIT vp<[[AVL:%.+]]> = sub ir<%N>, vp<[[EVL_PHI]]>
  ; IF-EVL-NEXT:   EMIT vp<[[EVL:%.+]]> = EXPLICIT-VECTOR-LENGTH vp<[[AVL]]>
  ; IF-EVL-NEXT:   CLONE ir<[[GEP1:%.+]]> = getelementptr inbounds ir<%b>, vp<[[EVL_PHI]]>

llvm/test/Transforms/LoopVectorize/vplan-predicate-switch.ll

@@ -18,7 +18,7 @@ define void @switch4_default_common_dest_with_case(ptr %start, ptr %end) {
 ; CHECK-NEXT: Successor(s): vector.body
 ; CHECK-EMPTY:
 ; CHECK-NEXT: vector.body:
-; CHECK-NEXT:   EMIT vp<[[CAN_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[CAN_IV_NEXT:%.+]]>, default.2 ]
+; CHECK-NEXT:   EMIT-SCALAR vp<[[CAN_IV:%.+]]> = phi [ ir<0>, ir-bb<vector.ph> ], [ vp<[[CAN_IV_NEXT:%.+]]>, default.2 ]
 ; CHECK-NEXT:   vp<[[STEPS:%.+]]> = SCALAR-STEPS vp<[[CAN_IV]]>, ir<1>, ir<2>
 ; CHECK-NEXT:   EMIT vp<[[PTR:%.+]]> = ptradd ir<%start>, vp<[[STEPS]]>
 ; CHECK-NEXT:   vp<[[WIDE_PTR:%.+]]> = vector-pointer vp<[[PTR]]>

llvm/unittests/Transforms/Vectorize/VPlanVerifierTest.cpp

@@ -171,7 +171,7 @@ TEST_F(VPVerifierTest, VPPhiIncomingValueDoesntDominateIncomingBlock) {
   EXPECT_STREQ("Incoming def at index 0 does not dominate incoming block!\n"
                "  EMIT vp<%2> = add ir<0>\n"
                "  does not dominate preheader for\n"
-               "  EMIT vp<%1> = phi [ vp<%2>, preheader ]",
+               "  EMIT-SCALAR vp<%1> = phi [ vp<%2>, preheader ]",
                ::testing::internal::GetCapturedStderr().c_str());
 #else
   EXPECT_STREQ("Incoming def at index 0 does not dominate incoming block!\n", ::