[llvm] [mlir] andrzej/disable flat transpose scalable (PR #115338)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Andrzej Warzyński (banach-space)

<details>
<summary>Changes</summary>

- **[ValueTracking] Don't special case depth for phi of select (#<!-- -->114996)**
- **[mlir][vector] Disable `vector.flat_transpose` for scalable vectors (#<!-- -->102573)**


---
Full diff: https://github.com/llvm/llvm-project/pull/115338.diff


3 Files Affected:

- (modified) llvm/lib/Analysis/ValueTracking.cpp (+8-10) 
- (modified) mlir/include/mlir/Dialect/Vector/IR/VectorOps.td (+6-2) 
- (modified) mlir/test/Dialect/Vector/invalid.mlir (+9) 


``````````diff
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 37cd4caaca71df..ed3fa35c5b8610 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -1565,20 +1565,12 @@ static void computeKnownBitsFromOperator(const Operator *I,
         // Skip direct self references.
         if (IncValue == P) continue;
 
-        // Recurse, but cap the recursion to one level, because we don't
-        // want to waste time spinning around in loops.
-        // TODO: See if we can base recursion limiter on number of incoming phi
-        // edges so we don't overly clamp analysis.
-        unsigned IncDepth = MaxAnalysisRecursionDepth - 1;
-
         // If the Use is a select of this phi, use the knownbit of the other
         // operand to break the recursion.
         if (auto *SI = dyn_cast<SelectInst>(IncValue)) {
-          if (SI->getTrueValue() == P || SI->getFalseValue() == P) {
+          if (SI->getTrueValue() == P || SI->getFalseValue() == P)
             IncValue = SI->getTrueValue() == P ? SI->getFalseValue()
                                                : SI->getTrueValue();
-            IncDepth = Depth + 1;
-          }
         }
 
         // Change the context instruction to the "edge" that flows into the
@@ -1589,7 +1581,13 @@ static void computeKnownBitsFromOperator(const Operator *I,
         RecQ.CxtI = P->getIncomingBlock(u)->getTerminator();
 
         Known2 = KnownBits(BitWidth);
-        computeKnownBits(IncValue, DemandedElts, Known2, IncDepth, RecQ);
+
+        // Recurse, but cap the recursion to one level, because we don't
+        // want to waste time spinning around in loops.
+        // TODO: See if we can base recursion limiter on number of incoming phi
+        // edges so we don't overly clamp analysis.
+        computeKnownBits(IncValue, DemandedElts, Known2,
+                         MaxAnalysisRecursionDepth - 1, RecQ);
 
         // See if we can further use a conditional branch into the phi
         // to help us determine the range of the value.
diff --git a/mlir/include/mlir/Dialect/Vector/IR/VectorOps.td b/mlir/include/mlir/Dialect/Vector/IR/VectorOps.td
index 3f45d0804e0450..6fe897cca79926 100644
--- a/mlir/include/mlir/Dialect/Vector/IR/VectorOps.td
+++ b/mlir/include/mlir/Dialect/Vector/IR/VectorOps.td
@@ -2770,11 +2770,11 @@ def Vector_FlatTransposeOp : Vector_Op<"flat_transpose", [Pure,
                  TCresVTEtIsSameAsOpBase<0, 0>>]>,
     Arguments<(
       // TODO: tighten vector element types that make sense.
-      ins VectorOfRankAndType<[1],
+      ins FixedVectorOfRankAndType<[1],
             [AnySignlessInteger, AnySignedInteger, Index, AnyFloat]>:$matrix,
           I32Attr:$rows, I32Attr:$columns)>,
     Results<(
-      outs VectorOfRankAndType<[1],
+      outs FixedVectorOfRankAndType<[1],
              [AnySignlessInteger, AnySignedInteger, Index, AnyFloat]>:$res)> {
   let summary = "Vector matrix transposition on flattened 1-D MLIR vectors";
   let description = [{
@@ -2789,6 +2789,10 @@ def Vector_FlatTransposeOp : Vector_Op<"flat_transpose", [Pure,
     a 2-D matrix with <rows> rows and <columns> columns, and returns the
     transposed matrix in flattened form in 'res'.
 
+    Note, the corresponding LLVM intrinsic, `@llvm.matrix.transpose.*`, does not
+    support scalable vectors. Hence, this Op is only available for fixed-width
+    vectors. Also see:
+
     Also see:
 
     http://llvm.org/docs/LangRef.html#llvm-matrix-transpose-intrinsic
diff --git a/mlir/test/Dialect/Vector/invalid.mlir b/mlir/test/Dialect/Vector/invalid.mlir
index 56039d04549aa5..d591c60acb64e7 100644
--- a/mlir/test/Dialect/Vector/invalid.mlir
+++ b/mlir/test/Dialect/Vector/invalid.mlir
@@ -1900,3 +1900,12 @@ func.func @matrix_multiply_scalable(%a: vector<[4]xf64>, %b: vector<4xf64>) {
 
   return
 }
+
+// -----
+
+func.func @flat_transpose_scalable(%arg0: vector<[16]xf32>) -> vector<[16]xf32> {
+  // expected-error @+1 {{'vector.flat_transpose' op operand #0 must be fixed-length vector of signless integer or signed integer or index or floating-point values of ranks 1, but got 'vector<[16]xf32>'}}
+  %0 = vector.flat_transpose %arg0 { rows = 4: i32, columns = 4: i32 }
+     : vector<[16]xf32> -> vector<[16]xf32>
+  return %0 : vector<[16]xf32>
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/115338