[llvm] r260892 - Tweak the LICM code to reuse the first sub-loop instead of creating a new one
Roman Gareev via llvm-commits
llvm-commits at lists.llvm.org
Mon Feb 15 06:48:51 PST 2016
Author: romangareev
Date: Mon Feb 15 08:48:50 2016
New Revision: 260892
URL: http://llvm.org/viewvc/llvm-project?rev=260892&view=rev
Log:
Tweak the LICM code to reuse the first sub-loop instead of creating a new one
LICM starts with an *empty* AST, and then merges in each sub-loop. While the
add code is appropriate for sub-loop 2 and up, it's utterly unnecessary for
sub-loop 1. If the AST starts off empty, we can just clone/move the contents
of the subloop into the containing AST.
Reviewed-by: Philip Reames <listmail at philipreames.com>
Differential Revision: http://reviews.llvm.org/D16753
Modified:
llvm/trunk/lib/Transforms/Scalar/LICM.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LICM.cpp?rev=260892&r1=260891&r2=260892&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp Mon Feb 15 08:48:50 2016
@@ -164,6 +164,11 @@ namespace {
/// Simple Analysis hook. Delete loop L from alias set map.
void deleteAnalysisLoop(Loop *L) override;
+
+ /// Returns an owning pointer to an alias set which incorporates aliasing
+ /// info from all subloops of L, but does not include instructions in L
+ /// itself.
+ AliasSetTracker *collectAliasInfoFromSubLoops(Loop *L);
};
}
@@ -202,20 +207,7 @@ bool LICM::runOnLoop(Loop *L, LPPassMana
assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form.");
- CurAST = new AliasSetTracker(*AA);
- // Collect Alias info from subloops.
- for (Loop *InnerL : L->getSubLoops()) {
- AliasSetTracker *InnerAST = LoopToAliasSetMap[InnerL];
- assert(InnerAST && "Where is my AST?");
-
- // What if InnerLoop was modified by other passes ?
- CurAST->add(*InnerAST);
-
- // Once we've incorporated the inner loop's AST into ours, we don't need the
- // subloop's anymore.
- delete InnerAST;
- LoopToAliasSetMap.erase(InnerL);
- }
+ CurAST = collectAliasInfoFromSubLoops(L);
CurLoop = L;
@@ -1065,6 +1057,32 @@ bool llvm::promoteLoopAccessesToScalars(
return Changed;
}
+/// Returns an owning pointer to an alias set which incorporates aliasing info
+/// from all subloops of L, but does not include instructions in L itself.
+///
+AliasSetTracker *LICM::collectAliasInfoFromSubLoops(Loop *L) {
+ AliasSetTracker *CurAST = nullptr;
+ for (Loop *InnerL : L->getSubLoops()) {
+ AliasSetTracker *InnerAST = LoopToAliasSetMap[InnerL];
+ assert(InnerAST && "Where is my AST?");
+
+ if (CurAST != nullptr) {
+ // What if InnerLoop was modified by other passes ?
+ CurAST->add(*InnerAST);
+
+ // Once we've incorporated the inner loop's AST into ours, we don't need
+ // the subloop's anymore.
+ delete InnerAST;
+ } else {
+ CurAST = InnerAST;
+ }
+ LoopToAliasSetMap.erase(InnerL);
+ }
+ if (CurAST == nullptr)
+ CurAST = new AliasSetTracker(*AA);
+ return CurAST;
+}
+
/// Simple analysis hook. Clone alias set info.
///
void LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) {
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