[VectorCombine] Add test coverage for reduce(trunc(X)) -> trunc(reduce(X)) folds

Author: RKSimon

llvm/test/Transforms/VectorCombine/X86/reduction-of-truncations.ll

@@ -0,0 +1,89 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -S --passes=vector-combine -mtriple=x86_64-- -mcpu=x86-64    | FileCheck %s --check-prefixes=CHECK,X64
+; RUN: opt < %s -S --passes=vector-combine -mtriple=x86_64-- -mcpu=x86-64-v2 | FileCheck %s --check-prefixes=CHECK,X64
+; RUN: opt < %s -S --passes=vector-combine -mtriple=x86_64-- -mcpu=x86-64-v3 | FileCheck %s --check-prefixes=CHECK,X64
+; RUN: opt < %s -S --passes=vector-combine -mtriple=x86_64-- -mcpu=x86-64-v4 | FileCheck %s --check-prefixes=CHECK,AVX512
+
+;
+; Fold reduce(trunc(X)) -> trunc(reduce(X)) if more cost efficient
+;
+
+; TODO: Cheap AVX512 v8i64 -> v8i32 truncation
+define i32 @reduce_add_trunc_v8i64_i32(<8 x i64> %a0)  {
+; CHECK-LABEL: @reduce_add_trunc_v8i64_i32(
+; CHECK-NEXT:    [[TR:%.*]] = trunc <8 x i64> [[A0:%.*]] to <8 x i32>
+; CHECK-NEXT:    [[RED:%.*]] = tail call i32 @llvm.vector.reduce.add.v8i32(<8 x i32> [[TR]])
+; CHECK-NEXT:    ret i32 [[RED]]
+;
+  %tr = trunc <8 x i64> %a0 to <8 x i32>
+  %red = tail call i32 @llvm.vector.reduce.add.v8i32(<8 x i32> %tr)
+  ret i32 %red
+}
+declare i32 @llvm.vector.reduce.add.v8i32(<8 x i32>)
+
+; TODO: No legal vXi8 multiplication so vXi16 is always cheaper
+define i8 @reduce_mul_trunc_v16i16_i8(<16 x i16> %a0)  {
+; CHECK-LABEL: @reduce_mul_trunc_v16i16_i8(
+; CHECK-NEXT:    [[TR:%.*]] = trunc <16 x i16> [[A0:%.*]] to <16 x i8>
+; CHECK-NEXT:    [[RED:%.*]] = tail call i8 @llvm.vector.reduce.mul.v16i8(<16 x i8> [[TR]])
+; CHECK-NEXT:    ret i8 [[RED]]
+;
+  %tr = trunc <16 x i16> %a0 to <16 x i8>
+  %red = tail call i8 @llvm.vector.reduce.mul.v16i8(<16 x i8> %tr)
+  ret i8 %red
+}
+declare i8 @llvm.vector.reduce.mul.v16i8(<16 x i8>)
+
+define i8 @reduce_or_trunc_v8i32_i8(<8 x i32> %a0)  {
+; CHECK-LABEL: @reduce_or_trunc_v8i32_i8(
+; CHECK-NEXT:    [[TR:%.*]] = trunc <8 x i32> [[A0:%.*]] to <8 x i8>
+; CHECK-NEXT:    [[RED:%.*]] = tail call i8 @llvm.vector.reduce.or.v8i8(<8 x i8> [[TR]])
+; CHECK-NEXT:    ret i8 [[RED]]
+;
+  %tr = trunc <8 x i32> %a0 to <8 x i8>
+  %red = tail call i8 @llvm.vector.reduce.or.v8i32(<8 x i8> %tr)
+  ret i8 %red
+}
+declare i32 @llvm.vector.reduce.or.v8i8(<8 x i8>)
+
+define i8 @reduce_xor_trunc_v16i64_i8(<16 x i64> %a0)  {
+; CHECK-LABEL: @reduce_xor_trunc_v16i64_i8(
+; CHECK-NEXT:    [[TR:%.*]] = trunc <16 x i64> [[A0:%.*]] to <16 x i8>
+; CHECK-NEXT:    [[RED:%.*]] = tail call i8 @llvm.vector.reduce.xor.v16i8(<16 x i8> [[TR]])
+; CHECK-NEXT:    ret i8 [[RED]]
+;
+  %tr = trunc <16 x i64> %a0 to <16 x i8>
+  %red = tail call i8 @llvm.vector.reduce.xor.v16i8(<16 x i8> %tr)
+  ret i8 %red
+}
+declare i8 @llvm.vector.reduce.xor.v16i8(<16 x i8>)
+
+; Negative Test: vXi16 multiply is much cheaper than vXi64
+define i16 @reduce_mul_trunc_v8i64_i16(<8 x i64> %a0)  {
+; CHECK-LABEL: @reduce_mul_trunc_v8i64_i16(
+; CHECK-NEXT:    [[TR:%.*]] = trunc <8 x i64> [[A0:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[RED:%.*]] = tail call i16 @llvm.vector.reduce.mul.v8i16(<8 x i16> [[TR]])
+; CHECK-NEXT:    ret i16 [[RED]]
+;
+  %tr = trunc <8 x i64> %a0 to <8 x i16>
+  %red = tail call i16 @llvm.vector.reduce.mul.v8i16(<8 x i16> %tr)
+  ret i16 %red
+}
+declare i16 @llvm.vector.reduce.mul.v8i16(<8 x i16>)
+
+; Negative Test: min/max reductions can't use pre-truncated types.
+define i8 @reduce_smin_trunc_v16i16_i8(<16 x i16> %a0)  {
+; CHECK-LABEL: @reduce_smin_trunc_v16i16_i8(
+; CHECK-NEXT:    [[TR:%.*]] = trunc <16 x i16> [[A0:%.*]] to <16 x i8>
+; CHECK-NEXT:    [[RED:%.*]] = tail call i8 @llvm.vector.reduce.smin.v16i8(<16 x i8> [[TR]])
+; CHECK-NEXT:    ret i8 [[RED]]
+;
+  %tr = trunc <16 x i16> %a0 to <16 x i8>
+  %red = tail call i8 @llvm.vector.reduce.smin.v16i8(<16 x i8> %tr)
+  ret i8 %red
+}
+declare i8 @llvm.vector.reduce.smin.v16i8(<16 x i8>)
+
+;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+; AVX512: {{.*}}
+; X64: {{.*}}