[llvm] dfec0b3 - [FuncSpec] Save compilation time by caching uses for propagation

[Bin Cheng via llvm-commits]

Author: Bin Cheng
Date: 2022-02-16T10:46:26+08:00
New Revision: dfec0b3053b9d433fa3770ff31bc540406db4ba8

URL: https://github.com/llvm/llvm-project/commit/dfec0b3053b9d433fa3770ff31bc540406db4ba8
DIFF: https://github.com/llvm/llvm-project/commit/dfec0b3053b9d433fa3770ff31bc540406db4ba8.diff

LOG: [FuncSpec] Save compilation time by caching uses for propagation

We only need to do propagation on use instructions of the original
value, rather than the replacing const value which might have lots
of irrelavant uses.  This is done by caching uses before replacing.

Differential Revision: https://reviews.llvm.org/D119815

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/FunctionSpecialization.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
index 9b6246b380bf6..832fa468dd3f9 100644
--- a/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp
@@ -344,12 +344,17 @@ class FunctionSpecializer {
     LLVM_DEBUG(dbgs() << "FnSpecialization: Replacing " << *V
                       << "\nFnSpecialization: with " << *Const << "\n");
 
-    V->replaceAllUsesWith(Const);
-
-    for (auto *U : Const->users())
+    // Record uses of V to avoid visiting irrelevant uses of const later.
+    SmallVector<Instruction *> UseInsts;
+    for (auto *U : V->users())
       if (auto *I = dyn_cast<Instruction>(U))
         if (Solver.isBlockExecutable(I->getParent()))
-          Solver.visit(I);
+          UseInsts.push_back(I);
+
+    V->replaceAllUsesWith(Const);
+
+    for (auto *I : UseInsts)
+      Solver.visit(I);
 
     // Remove the instruction from Block and Solver.
     if (auto *I = dyn_cast<Instruction>(V)) {