[SCEV] Don't create SCEV expressions that break LCSSA

Prevent `createNodeFromSelectLikePHI` from creating SCEV expressions
that break LCSSA.

A better fix for the same issue is to teach SCEVExpander to not break
LCSSA by inserting PHI nodes at appropriate places.  That's planned for
the future.

Fixes PR25360.

llvm-svn: 251756

1 files changed, 33 insertions, 0 deletions

diff --git a/llvm/test/Transforms/IndVarSimplify/pr25360.ll b/llvm/test/Transforms/IndVarSimplify/pr25360.ll
new file mode 100644
index 00000000000..9f6df7051ea
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/pr25360.ll
@@ -0,0 +1,33 @@
+; RUN: opt -indvars -S < %s | FileCheck %s
+
+
+; Ensure that does not crash
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @f() {
+; CHECK-LABEL: @f(
+entry:
+  br label %for.end
+
+for.condt:                         ; preds = %for.end
+  br i1 true, label %for.cond.0, label %for.end
+
+for.end:                                          ; preds = %for.body.3
+  %inc = select i1 undef, i32 2, i32 1
+  br i1 false, label %for.condt, label %for.cond.0
+
+for.cond.0:                       ; preds = %for.end, %for.condt
+  %init = phi i32 [ 0, %for.condt ], [ %inc, %for.end ]
+  br i1 true, label %for.end.13, label %for.body.9
+
+for.body.9:                                       ; preds = %for.body.9, %for.cond.0
+  %p1.addr.22 = phi i32 [ %inc10, %for.body.9 ], [ %init, %for.cond.0 ]
+  %inc10 = add i32 %p1.addr.22, 1
+  br i1 true, label %for.end.13, label %for.body.9
+
+for.end.13:                                       ; preds = %for.cond.7.for.end.13_crit_edge, %for.cond.0
+  %p1.addr.2.lcssa = phi i32 [ %inc10, %for.body.9 ], [ %init, %for.cond.0 ]
+  ret void
+}