[llvm] 205246c - [CompileTime] [Passes] Avoid computing unnecessary analyses. NFC

[Anna Thomas via llvm-commits]

Author: Anna Thomas
Date: 2022-04-29T10:00:06-04:00
New Revision: 205246cb64358aa6f03b54d47d73708122d76bbf

URL: https://github.com/llvm/llvm-project/commit/205246cb64358aa6f03b54d47d73708122d76bbf
DIFF: https://github.com/llvm/llvm-project/commit/205246cb64358aa6f03b54d47d73708122d76bbf.diff

LOG: [CompileTime] [Passes] Avoid computing unnecessary analyses. NFC

Similar to c515b2f39e77, If there are no loops in the function as seen
through LI, we should avoid computing the remaining expensive analyses
(such as SCEV, BPI).  Reordered the analyses requests and early return
if there are no loops.

The logic of avoiding expensive analyses is applied to LoopVectorizer,
LoopLoadElimination and LoopUnrollPass, i.e. all function passes which operate
on loops.

This is an NFC with compile time improvement.

Differential Revision: https://reviews.llvm.org/D124529

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
    llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/test/Transforms/SCCP/preserve-analysis.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp b/llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
index 090653557301a..1877ac1dfd083 100644
--- a/llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopLoadElimination.cpp
@@ -706,8 +706,12 @@ FunctionPass *llvm::createLoopLoadEliminationPass() {
 
 PreservedAnalyses LoopLoadEliminationPass::run(Function &F,
                                                FunctionAnalysisManager &AM) {
-  auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
   auto &LI = AM.getResult<LoopAnalysis>(F);
+  // There are no loops in the function. Return before computing other expensive
+  // analyses.
+  if (LI.empty())
+    return PreservedAnalyses::all();
+  auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
   auto &TTI = AM.getResult<TargetIRAnalysis>(F);
   auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);

diff  --git a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
index 9a3cd07a7f98c..45fbf2a858529 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
@@ -1545,8 +1545,12 @@ PreservedAnalyses LoopFullUnrollPass::run(Loop &L, LoopAnalysisManager &AM,
 
 PreservedAnalyses LoopUnrollPass::run(Function &F,
                                       FunctionAnalysisManager &AM) {
-  auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
   auto &LI = AM.getResult<LoopAnalysis>(F);
+  // There are no loops in the function. Return before computing other expensive
+  // analyses.
+  if (LI.empty())
+    return PreservedAnalyses::all();
+  auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
   auto &TTI = AM.getResult<TargetIRAnalysis>(F);
   auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
   auto &AC = AM.getResult<AssumptionAnalysis>(F);

diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index fa95c9caf9e50..3bedf4bc17910 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -10732,8 +10732,12 @@ LoopVectorizeResult LoopVectorizePass::runImpl(
 
 PreservedAnalyses LoopVectorizePass::run(Function &F,
                                          FunctionAnalysisManager &AM) {
-    auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
     auto &LI = AM.getResult<LoopAnalysis>(F);
+    // There are no loops in the function. Return before computing other expensive
+    // analyses.
+    if (LI.empty())
+      return PreservedAnalyses::all();
+    auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
     auto &TTI = AM.getResult<TargetIRAnalysis>(F);
     auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
     auto &BFI = AM.getResult<BlockFrequencyAnalysis>(F);

diff  --git a/llvm/test/Transforms/SCCP/preserve-analysis.ll b/llvm/test/Transforms/SCCP/preserve-analysis.ll
index a332e73d2524a..86ae5d9a9375e 100644
--- a/llvm/test/Transforms/SCCP/preserve-analysis.ll
+++ b/llvm/test/Transforms/SCCP/preserve-analysis.ll
@@ -5,10 +5,8 @@
 
 ; NEW-PM-DAG: Running analysis: LoopAnalysis on test
 ; NEW-PM-DAG: Running analysis: DominatorTreeAnalysis on test
-; NEW-PM-DAG: Running analysis: AssumptionAnalysis on test
-; NEW-PM-DAG: Running analysis: TargetLibraryAnalysis on test
-; NEW-PM-DAG: Running analysis: TargetIRAnalysis on test
 ; NEW-PM: Running pass: SCCPPass on test
+; NEW-PM: Running analysis: TargetLibraryAnalysis on test
 ; NEW-PM-NOT: Running analysis: LoopAnalysis on test
 ; NEW-PM-NOT: Running analysis: DominatorTreeAnalysis on test
 ; NEW-PM-NOT: Running analysis: AssumptionAnalysis on test