[ARM] Use VT vector size, not the array size, for determining if a shuffle corresponds to a VREV instruction

This logic matches that of AArch64's REVMask detection.

Author: AZero13

llvm/lib/Target/ARM/ARMTargetTransformInfo.h

@@ -347,6 +347,7 @@ inline bool isVREVMask(ArrayRef<int> M, EVT VT, unsigned BlockSize) {
   if (EltSz != 8 && EltSz != 16 && EltSz != 32)
     return false;
 
+  unsigned NumElts = VT.getVectorNumElements();
   unsigned BlockElts = M[0] + 1;
   // If the first shuffle index is UNDEF, be optimistic.
   if (M[0] < 0)
@@ -355,7 +356,7 @@ inline bool isVREVMask(ArrayRef<int> M, EVT VT, unsigned BlockSize) {
   if (BlockSize <= EltSz || BlockSize != BlockElts * EltSz)
     return false;
 
-  for (unsigned i = 0, e = M.size(); i < e; ++i) {
+  for (unsigned i = 0; i < NumElts; ++i) {
     if (M[i] < 0)
       continue; // ignore UNDEF indices
     if ((unsigned)M[i] != (i - i % BlockElts) + (BlockElts - 1 - i % BlockElts))

llvm/test/Analysis/CostModel/ARM/shuffle.ll

@@ -103,11 +103,11 @@ define void @reverse() {
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 128 for instruction: %v8i32 = shufflevector <8 x i32> undef, <8 x i32> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %v2i64 = shufflevector <2 x i64> undef, <2 x i64> undef, <2 x i32> <i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 128 for instruction: %v4i64 = shufflevector <4 x i64> undef, <4 x i64> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
-; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v2f16 = shufflevector <2 x half> undef, <2 x half> undef, <2 x i32> <i32 1, i32 0>
-; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v4f16 = shufflevector <4 x half> undef, <4 x half> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %v2f16 = shufflevector <2 x half> undef, <2 x half> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %v4f16 = shufflevector <4 x half> undef, <4 x half> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 32 for instruction: %v8f16 = shufflevector <8 x half> undef, <8 x half> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %v16f16 = shufflevector <16 x half> undef, <16 x half> undef, <16 x i32> <i32 15, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
-; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v2f32 = shufflevector <2 x float> undef, <2 x float> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %v2f32 = shufflevector <2 x float> undef, <2 x float> undef, <2 x i32> <i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %v4f32 = shufflevector <4 x float> undef, <4 x float> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 32 for instruction: %v8f32 = shufflevector <8 x float> undef, <8 x float> undef, <8 x i32> <i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %v2f64 = shufflevector <2 x double> undef, <2 x double> undef, <2 x i32> <i32 1, i32 0>
@@ -254,11 +254,11 @@ define void @select() {
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 128 for instruction: %v8i32 = shufflevector <8 x i32> undef, <8 x i32> undef, <8 x i32> <i32 8, i32 1, i32 10, i32 11, i32 4, i32 5, i32 6, i32 15>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %v2i64 = shufflevector <2 x i64> undef, <2 x i64> undef, <2 x i32> <i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 128 for instruction: %v4i64 = shufflevector <4 x i64> undef, <4 x i64> undef, <4 x i32> <i32 0, i32 5, i32 2, i32 7>
-; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v2f16 = shufflevector <2 x half> undef, <2 x half> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %v2f16 = shufflevector <2 x half> undef, <2 x half> undef, <2 x i32> <i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %v4f16 = shufflevector <4 x half> undef, <4 x half> undef, <4 x i32> <i32 0, i32 5, i32 2, i32 7>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 32 for instruction: %v8f16 = shufflevector <8 x half> undef, <8 x half> undef, <8 x i32> <i32 8, i32 1, i32 10, i32 11, i32 4, i32 5, i32 6, i32 15>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %v16f16 = shufflevector <16 x half> undef, <16 x half> undef, <16 x i32> <i32 0, i32 17, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
-; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v2f32 = shufflevector <2 x float> undef, <2 x float> undef, <2 x i32> <i32 1, i32 0>
+; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %v2f32 = shufflevector <2 x float> undef, <2 x float> undef, <2 x i32> <i32 1, i32 0>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %v4f32 = shufflevector <4 x float> undef, <4 x float> undef, <4 x i32> <i32 0, i32 5, i32 2, i32 7>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 32 for instruction: %v8f32 = shufflevector <8 x float> undef, <8 x float> undef, <8 x i32> <i32 8, i32 1, i32 10, i32 11, i32 4, i32 5, i32 6, i32 15>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %v2f64 = shufflevector <2 x double> undef, <2 x double> undef, <2 x i32> <i32 1, i32 0>
@@ -333,7 +333,7 @@ define void @vrev2() {
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v4i32 = shufflevector <4 x i32> undef, <4 x i32> undef, <4 x i32> <i32 1, i32 0, i32 3, i32 2>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 128 for instruction: %v8i32 = shufflevector <8 x i32> undef, <8 x i32> undef, <8 x i32> <i32 1, i32 0, i32 3, i32 2, i32 5, i32 4, i32 7, i32 6>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 128 for instruction: %v4i64 = shufflevector <4 x i64> undef, <4 x i64> undef, <4 x i32> <i32 1, i32 0, i32 3, i32 2>
-; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v4f16 = shufflevector <4 x half> undef, <4 x half> undef, <4 x i32> <i32 1, i32 0, i32 3, i32 2>
+; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 16 for instruction: %v4f16 = shufflevector <4 x half> undef, <4 x half> undef, <4 x i32> <i32 1, i32 0, i32 3, i32 2>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v8f16 = shufflevector <8 x half> undef, <8 x half> undef, <8 x i32> <i32 1, i32 0, i32 3, i32 2, i32 5, i32 4, i32 7, i32 6>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 64 for instruction: %v16f16 = shufflevector <16 x half> undef, <16 x half> undef, <16 x i32> <i32 1, i32 0, i32 3, i32 2, i32 5, i32 4, i32 7, i32 6, i32 9, i32 8, i32 11, i32 10, i32 13, i32 12, i32 15, i32 14>
 ; CHECK-MVE-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: %v4f32 = shufflevector <4 x float> undef, <4 x float> undef, <4 x i32> <i32 1, i32 0, i32 3, i32 2>