Don't crash analyzing certain quadratics (addrec of {X,+,Y,+,1}).

We're still waiting on code that actually analyzes them properly.

llvm-svn: 58592

2 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index e0750053eb9..ceded879b0f 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -2604,6 +2604,11 @@ SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
     // The divisions must be performed as signed divisions.
     APInt NegB(-B);
     APInt TwoA( A << 1 );
+    if (TwoA.isMinValue()) {
+      SCEV *CNC = new SCEVCouldNotCompute();
+      return std::make_pair(CNC, CNC);
+    }
+
     ConstantInt *Solution1 = ConstantInt::get((NegB + SqrtVal).sdiv(TwoA));
     ConstantInt *Solution2 = ConstantInt::get((NegB - SqrtVal).sdiv(TwoA));
 
diff --git a/llvm/test/Analysis/ScalarEvolution/2008-11-02-QuadraticCrash.ll b/llvm/test/Analysis/ScalarEvolution/2008-11-02-QuadraticCrash.ll
new file mode 100644
index 00000000000..c6cb87fca14
--- /dev/null
+++ b/llvm/test/Analysis/ScalarEvolution/2008-11-02-QuadraticCrash.ll
@@ -0,0 +1,21 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution
+; PR1827
+
+declare void @use(i32)
+
+define void @foo() {
+entry:
+	br label %loop_1
+
+loop_1:		; preds = %loop_1, %entry
+	%a = phi i32 [ 2, %entry ], [ %b, %loop_1 ]		; <i32> [#uses=2]
+	%c = phi i32 [ 5, %entry ], [ %d, %loop_1 ]		; <i32> [#uses=1]
+	%b = add i32 %a, 1		; <i32> [#uses=1]
+	%d = add i32 %c, %a		; <i32> [#uses=3]
+	%A = icmp ult i32 %d, 50		; <i1> [#uses=1]
+	br i1 %A, label %loop_1, label %endloop
+
+endloop:		; preds = %loop_1
+	call void @use(i32 %d)
+	ret void
+}