[SCEV] Do not insert if it is already in cache

This is fix for the crash caused by ScalarEvolution::getTruncateExpr.

It expects that if it checked the condition that SCEV is not in UniqueSCEVs cache in
the beginning that it will not be there inside this method.

However during recursion and transformation/simplification for sub expression,
it is possible that these modifications will end up with the same SCEV as we started from.

So we must always check whether SCEV is in cache and do not insert item if it is already there.

Reviewers: sanjoy, mkazantsev, craig.topper	
Reviewed By: sanjoy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D41380

llvm-svn: 321472

2 files changed, 82 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 2a8088dc445..f34549ae52b 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -1268,7 +1268,11 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
     }
     if (!hasTrunc)
       return getAddExpr(Operands);
-    UniqueSCEVs.FindNodeOrInsertPos(ID, IP);  // Mutates IP, returns NULL.
+    // In spite we checked in the beginning that ID is not in the cache,
+    // it is possible that during recursion and different modification
+    // ID came to cache, so if we found it, just return it.
+    if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP))
+      return S;
   }
 
   // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
@@ -1284,7 +1288,11 @@ const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
     }
     if (!hasTrunc)
       return getMulExpr(Operands);
-    UniqueSCEVs.FindNodeOrInsertPos(ID, IP);  // Mutates IP, returns NULL.
+    // In spite we checked in the beginning that ID is not in the cache,
+    // it is possible that during recursion and different modification
+    // ID came to cache, so if we found it, just return it.
+    if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP))
+      return S;
   }
 
   // If the input value is a chrec scev, truncate the chrec's operands.
diff --git a/llvm/test/Analysis/ScalarEvolution/truncate.ll b/llvm/test/Analysis/ScalarEvolution/truncate.ll
new file mode 100644
index 00000000000..e9bd39d7a26
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/truncate.ll
@@ -0,0 +1,72 @@
+; RUN: opt < %s -analyze -scalar-evolution
+; RUN: opt < %s -passes='print<scalar-evolution>'
+; Regression test for assert ScalarEvolution::getTruncateExpr.
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @snork(i8* %arg, i8 %arg1, i64 %arg2) {
+bb:
+  br label %bb12
+
+bb3:                                              ; preds = %bb34
+  br i1 true, label %bb4, label %bb12
+
+bb4:                                              ; preds = %bb3
+  br label %bb6
+
+bb5:                                              ; preds = %bb6
+  ret void
+
+bb6:                                              ; preds = %bb6, %bb4
+  %tmp = phi i64 [ %tmp28, %bb4 ], [ %tmp10, %bb6 ]
+  %tmp7 = phi i32 [ 3, %bb4 ], [ %tmp11, %bb6 ]
+  %tmp8 = trunc i64 %tmp to i32
+  %tmp9 = sdiv i32 %tmp8, %tmp7
+  %tmp10 = add i64 %tmp, -1
+  %tmp11 = add i32 %tmp9, %tmp7
+  br i1 true, label %bb5, label %bb6
+
+bb12:                                             ; preds = %bb3, %bb
+  br label %bb13
+
+bb13:                                             ; preds = %bb34, %bb12
+  %tmp14 = phi i64 [ %arg2, %bb12 ], [ %tmp28, %bb34 ]
+  %tmp15 = phi i8 [ %arg1, %bb12 ], [ %tmp26, %bb34 ]
+  %tmp16 = phi i32 [ 1, %bb12 ], [ %tmp35, %bb34 ]
+  %tmp17 = add i8 %tmp15, -1
+  %tmp18 = sext i8 %tmp17 to i64
+  %tmp19 = sub i64 1, %tmp14
+  %tmp20 = add i64 %tmp19, %tmp18
+  %tmp21 = trunc i64 %tmp20 to i32
+  %tmp22 = icmp eq i32 %tmp21, 0
+  br i1 %tmp22, label %bb32, label %bb23
+
+bb23:                                             ; preds = %bb13
+  br i1 true, label %bb25, label %bb24
+
+bb24:                                             ; preds = %bb23
+  br label %bb25
+
+bb25:                                             ; preds = %bb24, %bb23
+  %tmp26 = add i8 %tmp15, -2
+  %tmp27 = sext i8 %tmp26 to i64
+  %tmp28 = sub i64 %tmp27, %tmp20
+  %tmp29 = trunc i64 %tmp28 to i32
+  %tmp30 = icmp eq i32 %tmp29, 0
+  br i1 %tmp30, label %bb31, label %bb34
+
+bb31:                                             ; preds = %bb25
+  br label %bb33
+
+bb32:                                             ; preds = %bb13
+  br label %bb33
+
+bb33:                                             ; preds = %bb32, %bb31
+  unreachable
+
+bb34:                                             ; preds = %bb25
+  %tmp35 = add nuw nsw i32 %tmp16, 2
+  %tmp36 = icmp ugt i32 %tmp16, 52
+  br i1 %tmp36, label %bb3, label %bb13
+}