[llvm-branch-commits] [llvm] a4914dc - [SLP] do not traverse constant uses

[Sanjay Patel via llvm-branch-commits]

Author: Anton Rapetov
Date: 2021-01-22T08:14:09-05:00
New Revision: a4914dc1f2b4a49cf488d3be7a01fe7238c889d8

URL: https://github.com/llvm/llvm-project/commit/a4914dc1f2b4a49cf488d3be7a01fe7238c889d8
DIFF: https://github.com/llvm/llvm-project/commit/a4914dc1f2b4a49cf488d3be7a01fe7238c889d8.diff

LOG: [SLP] do not traverse constant uses

Walking the use list of a Constant (particularly, ConstantData)
is not scalable, since a given constant may be used by many
instructinos in many functions in many modules.

Differential Revision: https://reviews.llvm.org/D94713

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index cee388e62bf2..78ce4870588c 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -987,6 +987,14 @@ class BoUpSLP {
       std::array<std::pair<Value *, int>, 2> Values = {{LHS, RHS}};
       for (int Idx = 0, IdxE = Values.size(); Idx != IdxE; ++Idx) {
         Value *V = Values[Idx].first;
+        if (isa<Constant>(V)) {
+          // Since this is a function pass, it doesn't make semantic sense to
+          // walk the users of a subclass of Constant. The users could be in
+          // another function, or even another module that happens to be in
+          // the same LLVMContext.
+          continue;
+        }
+
         // Calculate the absolute lane, using the minimum relative lane of LHS
         // and RHS as base and Idx as the offset.
         int Ln = std::min(LHS.second, RHS.second) + Idx;