[PATCH] D42378: [X86][SSE] Avoid calls to combineX86ShufflesRecursively that can't combine to target shuffles (PR32037)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: spatel, andreadb, craig.topper, rnk, hfinkel.

Don't bother making recursive calls to combineX86ShufflesRecursively if we have more shuffle source operands than will be combined together with the remaining recursive depth.

See https://bugs.llvm.org/show_bug.cgi?id=32037#c26 and https://bugs.llvm.org/show_bug.cgi?id=32037#c27 for the reduction in compile times from this patch.


Repository:
  rL LLVM

https://reviews.llvm.org/D42378

Files:
  lib/Target/X86/X86ISelLowering.cpp


Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -29244,7 +29244,8 @@
     TargetLowering::DAGCombinerInfo &DCI, const X86Subtarget &Subtarget) {
   // Bound the depth of our recursive combine because this is ultimately
   // quadratic in nature.
-  if (Depth > 8)
+  const int MaxRecursionDepth = 8;
+  if (Depth > MaxRecursionDepth)
     return SDValue();
 
   // Directly rip through bitcasts to find the underlying operand.
@@ -29397,13 +29398,17 @@
   // See if we can recurse into each shuffle source op (if it's a target
   // shuffle). The source op should only be combined if it either has a
   // single use (i.e. current Op) or all its users have already been combined.
-  for (int i = 0, e = Ops.size(); i < e; ++i)
-    if (Ops[i].getNode()->hasOneUse() ||
-        SDNode::areOnlyUsersOf(CombinedNodes, Ops[i].getNode()))
-      if (SDValue Res = combineX86ShufflesRecursively(
-              Ops, i, Root, Mask, CombinedNodes, Depth + 1, HasVariableMask,
-              DAG, DCI, Subtarget))
-        return Res;
+  // Don't recurse if we already have more source ops than we can combine in
+  // the remaining recursion depth.
+  if (Ops.size() < (unsigned)(MaxRecursionDepth - Depth)) {
+    for (int i = 0, e = Ops.size(); i < e; ++i)
+      if (Ops[i].getNode()->hasOneUse() ||
+          SDNode::areOnlyUsersOf(CombinedNodes, Ops[i].getNode()))
+        if (SDValue Res = combineX86ShufflesRecursively(
+                Ops, i, Root, Mask, CombinedNodes, Depth + 1, HasVariableMask,
+                DAG, DCI, Subtarget))
+          return Res;
+  }
 
   // Attempt to constant fold all of the constant source ops.
   if (SDValue Cst = combineX86ShufflesConstants(


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