[mlir][affine] Add unit tests for isProjectedPermutation (#114775)

The only way to test `isProjectedPermutation` is through unit tests. The
concept of "projected permutations" is tricky to document and these
tests are a good source documentation of the expected/intended
behavoiur. Hence these additional unit tests.

Author: banach-space

mlir/unittests/IR/AffineMapTest.cpp

@@ -21,3 +21,58 @@ TEST(AffineMapTest, inferMapFromAffineExprs) {
   map.replace(replacements);
   EXPECT_EQ(map, map);
 }
+
+TEST(AffineMapTest, isProjectedPermutation) {
+  MLIRContext ctx;
+  OpBuilder b(&ctx);
+
+  // 1. Empty map
+  AffineMap map1 = b.getEmptyAffineMap();
+  EXPECT_TRUE(map1.isProjectedPermutation());
+
+  // 2. Map with a symbol
+  AffineMap map2 = AffineMap::get(0, 1, &ctx);
+  EXPECT_FALSE(map2.isProjectedPermutation());
+
+  // 3. The result map is {0} and zero results are _allowed_.
+  auto zero = b.getAffineConstantExpr(0);
+  AffineMap map3 = AffineMap::get(1, 0, {zero}, &ctx);
+  EXPECT_TRUE(map3.isProjectedPermutation(/*allowZeroInResults=*/true));
+
+  // 4. The result map is {0} and zero results are _not allowed_
+  AffineMap map4 = AffineMap::get(1, 0, {zero}, &ctx);
+  EXPECT_FALSE(map4.isProjectedPermutation(/*allowZeroInResults=*/false));
+
+  // 5. The number of results > inputs
+  AffineMap map5 = AffineMap::get(1, 0, {zero, zero}, &ctx);
+  EXPECT_FALSE(map5.isProjectedPermutation(/*allowZeroInResults=*/true));
+
+  // 6. A constant result that's not a {0}
+  auto one = b.getAffineConstantExpr(1);
+  AffineMap map6 = AffineMap::get(1, 0, {one}, &ctx);
+  EXPECT_FALSE(map6.isProjectedPermutation(/*allowZeroInResults=*/true));
+
+  // 7. Not a dim expression
+  auto d0 = b.getAffineDimExpr(0);
+  auto d1 = b.getAffineDimExpr(1);
+
+  auto sum = d0 + d1;
+  AffineMap map7 = AffineMap::get(2, 0, {sum}, &ctx);
+  EXPECT_FALSE(map7.isProjectedPermutation());
+
+  // 8. (d0, d1, d2, d3, d4, d5) ->(d5, d3, d0, d1, d2, d4)
+  auto d2 = b.getAffineDimExpr(2);
+  auto d3 = b.getAffineDimExpr(3);
+  auto d4 = b.getAffineDimExpr(4);
+  auto d5 = b.getAffineDimExpr(5);
+  AffineMap map8 = AffineMap::get(6, 0, {d5, d3, d0, d1, d2, d4}, &ctx);
+  EXPECT_TRUE(map8.isProjectedPermutation());
+
+  // 9. (d0, d1, d2, d3, d4, d5) ->(d5, d3, d0 + d1, d2, d4)
+  AffineMap map9 = AffineMap::get(6, 0, {d5, d3, sum, d2, d4}, &ctx);
+  EXPECT_FALSE(map9.isProjectedPermutation());
+
+  // 10. (d0, d1, d2, d3, d4, d5) ->(d5, d3, d2, d4)
+  AffineMap map10 = AffineMap::get(6, 0, {d5, d3, d2, d4}, &ctx);
+  EXPECT_TRUE(map10.isProjectedPermutation());
+}