Identify and hoist definitively invariant loads
As a first step in the direction of assumed invariant loads (loads
that are not written in some context) we now detect and hoist
definitively invariant loads. These invariant loads will be preloaded
in the code generation and used in the optimized version of the SCoP.
If the load is only conditionally executed the preloaded version will
also only be executed under the same condition, hence we will never
access memory that wouldn't have been accessed otherwise. This is also
the most distinguishing feature to licm.
As hoisting can make statements empty we will simplify the SCoP and
remove empty statements that would otherwise cause artifacts in the
code generation.
Differential Revision: http://reviews.llvm.org/D13194
llvm-svn: 248861
diff --git a/polly/lib/CodeGen/CodeGeneration.cpp b/polly/lib/CodeGen/CodeGeneration.cpp
index 96d0938..53aac25 100644
--- a/polly/lib/CodeGen/CodeGeneration.cpp
+++ b/polly/lib/CodeGen/CodeGeneration.cpp
@@ -146,8 +146,9 @@
auto SplitBlock = StartBlock->getSinglePredecessor();
Builder.SetInsertPoint(SplitBlock->getTerminator());
NodeBuilder.addParameters(S.getContext());
+ NodeBuilder.preloadInvariantLoads();
Value *RTC = buildRTC(Builder, NodeBuilder.getExprBuilder());
- SplitBlock->getTerminator()->setOperand(0, RTC);
+ Builder.GetInsertBlock()->getTerminator()->setOperand(0, RTC);
Builder.SetInsertPoint(StartBlock->begin());
NodeBuilder.create(AstRoot);