[PATCH] D49108: [CVP] Handle instructions with no user. No need to create CVPLattice state. This handles terminator instructions and more.

[Xin Tong via Phabricator via llvm-commits]

trentxintong created this revision.
trentxintong added reviewers: davide, mssimpso.

I tested this pass by concatenating all the code from the
llvm/lib/Analysis/ folder and do clang -g followed by opt
(~/llvmoss/build/bin/opt  -called-value-propagation analysis.dbg.ll
-time-passes -f -o out). I get
~7% speedup for the pass. I expect some of the gain come from skipping terminator
instructions.

I did not run CTMark, because I do not expect this to show up measureably
in the benchmark.

Before patch:
=============

-------------------------------------------------------------------------
-------------------------------------------------------------------------

  ... Pass execution timing report ...

-------------------------------------------------------------------------
-------------------------------------------------------------------------

  Total Execution Time: 3.5970 seconds (3.5957 wall clock)
  
   ---User Time---   --System Time--   --User+System--   ---Wall Time---

- Name --- 2.0163 ( 59.2%)   0.1050 ( 54.8%)   2.1212 ( 59.0%)   2.1213 ( 59.0%)

Bitcode Writer

  0.6797 ( 20.0%)   0.0595 ( 31.1%)   0.7391 ( 20.5%)   0.7378 ( 20.5%)

Module Verifier

  0.7096 ( 20.8%)   0.0270 ( 14.1%)   0.7366 ( 20.5%)   0.7366 ( 20.5%)

Called Value Propagation

  3.4056 (100.0%)   0.1914 (100.0%)   3.5970 (100.0%)   3.5957 (100.0%)

Total

After patch:
============

-------------------------------------------------------------------------
-------------------------------------------------------------------------

  ... Pass execution timing report ...

-------------------------------------------------------------------------
-------------------------------------------------------------------------

  Total Execution Time: 3.4911 seconds (3.4896 wall clock)
  
   ---User Time---   --System Time--   --User+System--   ---Wall Time---

- Name --- 1.9794 ( 59.9%)   0.1050 ( 56.0%)   2.0844 ( 59.7%)   2.0844 ( 59.7%)

Bitcode Writer

  0.6717 ( 20.3%)   0.0546 ( 29.1%)   0.7263 ( 20.8%)   0.7247 ( 20.8%)

Module Verifier

  0.6525 ( 19.8%)   0.0280 ( 14.9%)   0.6804 ( 19.5%)   0.6805 ( 19.5%)

Called Value Propagation

  3.3036 (100.0%)   0.1876 (100.0%)   3.4911 (100.0%)   3.4896 (100.0%)

Total


Repository:
  rL LLVM

https://reviews.llvm.org/D49108

Files:
  lib/Transforms/IPO/CalledValuePropagation.cpp


Index: lib/Transforms/IPO/CalledValuePropagation.cpp
===================================================================
--- lib/Transforms/IPO/CalledValuePropagation.cpp
+++ lib/Transforms/IPO/CalledValuePropagation.cpp
@@ -345,6 +345,9 @@
   void visitInst(Instruction &I,
                  DenseMap<CVPLatticeKey, CVPLatticeVal> &ChangedValues,
                  SparseSolver<CVPLatticeKey, CVPLatticeVal> &SS) {
+    // Simply bail if this instruction has no user.
+    if (I.use_empty())
+      return;
     auto RegI = CVPLatticeKey(&I, IPOGrouping::Register);
     ChangedValues[RegI] = getOverdefinedVal();
   }


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