CodePrepare: Do not require canonical induction variables for scev based mode

llvm-svn: 177593

2 files changed, 72 insertions, 5 deletions

diff --git a/polly/lib/CodePreparation.cpp b/polly/lib/CodePreparation.cpp
index b1d48e04bda..b954e101929 100644
--- a/polly/lib/CodePreparation.cpp
+++ b/polly/lib/CodePreparation.cpp
@@ -13,6 +13,7 @@
 //
 //===----------------------------------------------------------------------===//
 #include "polly/LinkAllPasses.h"
+#include "polly/CodeGen/BlockGenerators.h"
 #include "polly/Support/ScopHelper.h"
 
 #include "llvm/IR/Instruction.h"
@@ -47,6 +48,7 @@ class CodePreparation : public FunctionPass {
 
   // LoopInfo to compute canonical induction variable.
   LoopInfo *LI;
+  ScalarEvolution *SE;
 
   // Clear the context.
   void clear();
@@ -92,11 +94,21 @@ bool CodePreparation::eliminatePHINodes(Function &F) {
     for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->getFirstNonPHI();
         iib != iie; ++iib)
       if (PHINode *PN = cast<PHINode>(iib)) {
-        if (Loop *L = LI->getLoopFor(ibb)) {
-          // Induction variable will be preserved.
-          if (L->getCanonicalInductionVariable() == PN) {
-            PreservedPNs.push_back(PN);
-            continue;
+        if (SCEVCodegen) {
+          if (SE->isSCEVable(PN->getType())) {
+            const SCEV *S = SE->getSCEV(PN);
+            if (!isa<SCEVUnknown>(S) && !isa<SCEVCouldNotCompute>(S)) {
+              PreservedPNs.push_back(PN);
+              continue;
+            }
+          }
+        } else {
+          if (Loop *L = LI->getLoopFor(ibb)) {
+            // Induction variable will be preserved.
+            if (L->getCanonicalInductionVariable() == PN) {
+              PreservedPNs.push_back(PN);
+              continue;
+            }
           }
         }
 
@@ -136,6 +148,7 @@ bool CodePreparation::eliminatePHINodes(Function &F) {
 
 void CodePreparation::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<LoopInfo>();
+  AU.addRequired<ScalarEvolution>();
 
   AU.addPreserved<LoopInfo>();
   AU.addPreserved<RegionInfo>();
@@ -145,6 +158,7 @@ void CodePreparation::getAnalysisUsage(AnalysisUsage &AU) const {
 
 bool CodePreparation::runOnFunction(Function &F) {
   LI = &getAnalysis<LoopInfo>();
+  SE = &getAnalysis<ScalarEvolution>();
 
   splitEntryBlockForAlloca(&F.getEntryBlock(), this);
 
diff --git a/polly/test/CodePreparation/if_condition.ll b/polly/test/CodePreparation/if_condition.ll
new file mode 100644
index 00000000000..fde60a25ec0
--- /dev/null
+++ b/polly/test/CodePreparation/if_condition.ll
@@ -0,0 +1,53 @@
+; RUN: opt %loadPolly -polly-prepare -S < %s | FileCheck %s
+; RUN: opt %loadPolly -polly-prepare -S -polly-codegen-scev < %s | FileCheck %s
+
+; void f(long A[], long N) {
+;   long i;
+;   for (i = 0; i < N; ++i)
+;     A[i] = i;
+; }
+
+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"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @f(i64* %A, i64 %N) nounwind {
+entry:
+  fence seq_cst
+  br label %for.i
+; CHECK: entry:
+; CHECK: %value.reg2mem = alloca i64
+; CHECK: br label %entry.split
+
+for.i:
+  %indvar = phi i64 [ 0, %entry ], [ %indvar.next, %merge ]
+  %scevgep = getelementptr i64* %A, i64 %indvar
+  %cmp = icmp eq i64 %indvar, 3
+  br i1 %cmp, label %then, label %else
+
+then:
+  %add_two = add i64 %indvar, 2
+  br label %merge
+; CHECK: then:
+; CHECK:   %add_two = add i64 %indvar, 2
+; CHECK:   store i64 %add_two, i64* %value.reg2mem
+; CHECK:   br label %merge
+
+else:
+  %add_three = add i64 %indvar, 4
+  br label %merge
+; CHECK: else:
+; CHECK:   %add_three = add i64 %indvar, 4
+; CHECK:   store i64 %add_three, i64* %value.reg2mem
+; CHECK:   br label %merge
+
+merge:
+  %value = phi i64 [ %add_two, %then ], [ %add_three, %else ]
+  store i64 %value, i64* %scevgep
+  %indvar.next = add nsw i64 %indvar, 1
+  %exitcond = icmp eq i64 %indvar.next, %N
+  br i1 %exitcond, label %return, label %for.i
+
+return:
+  fence seq_cst
+  ret void
+}