Avoid analyzing instructions in blocks not reachable from the entry block.
They are lots of trouble, and they don't matter. This fixes PR6559.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98103 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index b979f33..15f072d 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -3101,9 +3101,16 @@
return getUnknown(V);
unsigned Opcode = Instruction::UserOp1;
- if (Instruction *I = dyn_cast<Instruction>(V))
+ if (Instruction *I = dyn_cast<Instruction>(V)) {
Opcode = I->getOpcode();
- else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
+
+ // Don't attempt to analyze instructions in blocks that aren't
+ // reachable. Such instructions don't matter, and they aren't required
+ // to obey basic rules for definitions dominating uses which this
+ // analysis depends on.
+ if (!DT->isReachableFromEntry(I->getParent()))
+ return getUnknown(V);
+ } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
Opcode = CE->getOpcode();
else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
return getConstant(CI);
diff --git a/test/Analysis/ScalarEvolution/unreachable-code.ll b/test/Analysis/ScalarEvolution/unreachable-code.ll
new file mode 100644
index 0000000..51d9398
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/unreachable-code.ll
@@ -0,0 +1,13 @@
+; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
+
+; CHECK: %t = add i64 %t, 1
+; CHECK: --> %t
+
+define void @foo() {
+entry:
+ ret void
+
+dead:
+ %t = add i64 %t, 1
+ ret void
+}