[Polly] [PPCGCodeGeneration] Handle failing of invariant load hoisting gracefully.

To do this, we replicate what `CodeGeneration` does. We expose
`markNodeUnreachable` from `CodeGeneration` to `PPCGCodeGeneration`.

Differential Revision: https://reviews.llvm.org/D36457

llvm-svn: 310350

1 files changed, 26 insertions, 9 deletions

diff --git a/polly/lib/CodeGen/PPCGCodeGeneration.cpp b/polly/lib/CodeGen/PPCGCodeGeneration.cpp
index d3a13edc3b6..3ab1b6496c3 100644
--- a/polly/lib/CodeGen/PPCGCodeGeneration.cpp
+++ b/polly/lib/CodeGen/PPCGCodeGeneration.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "polly/CodeGen/PPCGCodeGeneration.h"
+#include "polly/CodeGen/CodeGeneration.h"
 #include "polly/CodeGen/IslAst.h"
 #include "polly/CodeGen/IslNodeBuilder.h"
 #include "polly/CodeGen/Utils.h"
@@ -3373,7 +3374,6 @@ public:
     // TODO: Handle LICM
     auto SplitBlock = StartBlock->getSinglePredecessor();
     Builder.SetInsertPoint(SplitBlock->getTerminator());
-    NodeBuilder.addParameters(S->getContext().release());
 
     isl_ast_build *Build = isl_ast_build_alloc(S->getIslCtx());
     isl_ast_expr *Condition = IslAst::buildRunCondition(*S, Build);
@@ -3383,17 +3383,34 @@ public:
 
     // preload invariant loads. Note: This should happen before the RTC
     // because the RTC may depend on values that are invariant load hoisted.
-    if (!NodeBuilder.preloadInvariantLoads())
-      report_fatal_error("preloading invariant loads failed in function: " +
-                         S->getFunction().getName() +
-                         " | Scop Region: " + S->getNameStr());
+    if (!NodeBuilder.preloadInvariantLoads()) {
+      DEBUG(dbgs() << "preloading invariant loads failed in function: " +
+                          S->getFunction().getName() +
+                          " | Scop Region: " + S->getNameStr());
+      // adjust the dominator tree accordingly.
+      auto *ExitingBlock = StartBlock->getUniqueSuccessor();
+      assert(ExitingBlock);
+      auto *MergeBlock = ExitingBlock->getUniqueSuccessor();
+      assert(MergeBlock);
+      polly::markBlockUnreachable(*StartBlock, Builder);
+      polly::markBlockUnreachable(*ExitingBlock, Builder);
+      auto *ExitingBB = S->getExitingBlock();
+      assert(ExitingBB);
+
+      DT->changeImmediateDominator(MergeBlock, ExitingBB);
+      DT->eraseNode(ExitingBlock);
+      isl_ast_expr_free(Condition);
+      isl_ast_node_free(Root);
+    } else {
 
-    Value *RTC = NodeBuilder.createRTC(Condition);
-    Builder.GetInsertBlock()->getTerminator()->setOperand(0, RTC);
+      NodeBuilder.addParameters(S->getContext().release());
+      Value *RTC = NodeBuilder.createRTC(Condition);
+      Builder.GetInsertBlock()->getTerminator()->setOperand(0, RTC);
 
-    Builder.SetInsertPoint(&*StartBlock->begin());
+      Builder.SetInsertPoint(&*StartBlock->begin());
 
-    NodeBuilder.create(Root);
+      NodeBuilder.create(Root);
+    }
 
     /// In case a sequential kernel has more surrounding loops as any parallel
     /// kernel, the SCoP is probably mostly sequential. Hence, there is no