IslCodegen: Support for run-time conditions

llvm-svn: 194948

4 files changed, 55 insertions, 0 deletions

diff --git a/polly/include/polly/CodeGen/IslAst.h b/polly/include/polly/CodeGen/IslAst.h
index 023d12b27af..6b8a90ac253 100644
--- a/polly/include/polly/CodeGen/IslAst.h
+++ b/polly/include/polly/CodeGen/IslAst.h
@@ -33,6 +33,7 @@ class raw_ostream;
 }
 
 struct isl_ast_node;
+struct isl_ast_expr;
 struct isl_ast_build;
 struct isl_pw_multi_aff;
 
@@ -64,6 +65,14 @@ public:
 
   isl_ast_node *getAst();
 
+  /// @brief Get the run conditon.
+  ///
+  /// Only if the run condition evaluates at run-time to a non-zero value, the
+  /// assumptions that have been taken hold. If the run condition evaluates to
+  /// zero/false some assumptions do not hold and the original code needs to
+  /// be executed.
+  __isl_give isl_ast_expr *getRunCondition();
+
   bool runOnScop(Scop &S);
   void printScop(llvm::raw_ostream &OS) const;
   virtual void getAnalysisUsage(AnalysisUsage &AU) const;
diff --git a/polly/lib/CodeGen/IslAst.cpp b/polly/lib/CodeGen/IslAst.cpp
index 94cc65f4e16..629d86c94f4 100644
--- a/polly/lib/CodeGen/IslAst.cpp
+++ b/polly/lib/CodeGen/IslAst.cpp
@@ -464,6 +464,9 @@ bool IslAstInfo::runOnScop(Scop &Scop) {
 }
 
 __isl_give isl_ast_node *IslAstInfo::getAst() { return Ast->getAst(); }
+__isl_give isl_ast_expr *IslAstInfo::getRunCondition() {
+  return Ast->getRunCondition();
+}
 
 void IslAstInfo::printScop(raw_ostream &OS) const {
   Function *F = S->getRegion().getEntry()->getParent();
diff --git a/polly/lib/CodeGen/IslCodeGeneration.cpp b/polly/lib/CodeGen/IslCodeGeneration.cpp
index 465d1101d3a..cde2a54b80f 100644
--- a/polly/lib/CodeGen/IslCodeGeneration.cpp
+++ b/polly/lib/CodeGen/IslCodeGeneration.cpp
@@ -542,6 +542,7 @@ public:
 
   void addParameters(__isl_take isl_set *Context);
   void create(__isl_take isl_ast_node *Node);
+  IslExprBuilder &getExprBuilder() { return ExprBuilder; }
 
 private:
   IRBuilder<> &Builder;
@@ -1032,6 +1033,17 @@ public:
     IRBuilder<> Builder(StartBlock->begin());
 
     IslNodeBuilder NodeBuilder(Builder, this);
+
+    // Build condition that evaluates at run-time if all assumptions taken
+    // for the scop hold. If we detect some assumptions do not hold, the
+    // original code is executed.
+    Value *V = NodeBuilder.getExprBuilder().create(AstInfo.getRunCondition());
+    Value *Zero = ConstantInt::get(V->getType(), 0);
+    V = Builder.CreateICmp(CmpInst::ICMP_NE, Zero, V);
+    BasicBlock *PrevBB = StartBlock->getUniquePredecessor();
+    BranchInst *Branch = dyn_cast<BranchInst>(PrevBB->getTerminator());
+    Branch->setCondition(V);
+
     NodeBuilder.addParameters(S.getContext());
     NodeBuilder.create(Ast);
     return true;
diff --git a/polly/test/Isl/CodeGen/run-time-condition.ll b/polly/test/Isl/CodeGen/run-time-condition.ll
new file mode 100644
index 00000000000..9d57630abab
--- /dev/null
+++ b/polly/test/Isl/CodeGen/run-time-condition.ll
@@ -0,0 +1,31 @@
+; RUN: opt %loadPolly -basicaa -polly-codegen-isl -S %s | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @run-time-condition(i16* noalias %A, i16* noalias %B) {
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %indvar = phi i64 [ 0, %entry ], [ %inc, %for.body ]
+  %cmp = icmp slt i64 %indvar, 1024
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  %arrayidx = getelementptr inbounds i16* %B, i64 0
+  %load = load i16* %arrayidx
+  %add10 = add nsw i16 %load, 1
+  %arrayidx13 = getelementptr inbounds i16* %A, i64 %indvar
+  store i16 %add10, i16* %arrayidx13, align 2
+  %inc = add nsw i64 %indvar, 1
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  ret void
+}
+
+; The trivial case, no run-time checks required.
+;
+; CHECK: polly.split_new_and_old:
+; CHECK:  br i1 true, label %polly.start, label %for.cond