From 239fd44f7a68aae4b2e8b6f1738ef9e8fd4ddc01 Mon Sep 17 00:00:00 2001
From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Fri, 19 Oct 2012 16:37:30 +0000
Subject: [PATCH] SCEVExpander: Don't crash when trying to merge two constant
 phis.

Just constant fold them so they can't cause any trouble. Fixes PR12627.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166286 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ScalarEvolutionExpander.cpp      | 11 ++++++++
 .../2012-10-19-congruent-constant.ll          | 27 +++++++++++++++++++
 .../IndVarSimplify/no-iv-rewrite.ll           |  1 -
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/IndVarSimplify/2012-10-19-congruent-constant.ll

diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index 5c2a49e767f..f18c50e0709 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -1618,6 +1618,17 @@ unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
          PEnd = Phis.end(); PIter != PEnd; ++PIter) {
     PHINode *Phi = *PIter;
 
+    // Fold constant phis. They may be congruent to other constant phis and
+    // would confuse the logic below that expects proper IVs.
+    if (Value *V = Phi->hasConstantValue()) {
+      Phi->replaceAllUsesWith(V);
+      DeadInsts.push_back(Phi);
+      ++NumElim;
+      DEBUG_WITH_TYPE(DebugType, dbgs()
+                      << "INDVARS: Eliminated constant iv: " << *Phi << '\n');
+      continue;
+    }
+
     if (!SE.isSCEVable(Phi->getType()))
       continue;
 
diff --git a/test/Transforms/IndVarSimplify/2012-10-19-congruent-constant.ll b/test/Transforms/IndVarSimplify/2012-10-19-congruent-constant.ll
new file mode 100644
index 00000000000..5c478669d29
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/2012-10-19-congruent-constant.ll
@@ -0,0 +1,27 @@
+; RUN: opt -S -indvars < %s | FileCheck %s
+
+; PR12627
+define void @test1(i32 %x) nounwind uwtable ssp {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %phi1 = phi i1 [ false, %entry ], [ %cmpa, %for.body ]
+  %phi2 = phi i1 [ false, %entry ], [ %cmpb, %for.body ]
+  %i.07 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  tail call void @aux(i1 %phi1, i1 %phi2) nounwind
+  %cmpa = icmp sgt i32 %i.07, 200
+  %cmpb = icmp sgt i32 %i.07, 100
+  %inc = add nsw i32 %i.07, 1
+  %exitcond = icmp eq i32 %inc, 100
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  ret void
+
+; CHECK: @test1
+; CHECK-NOT: phi i1
+; CHECK: call void @aux(i1 false, i1 false)
+}
+
+declare void @aux(i1, i1)
diff --git a/test/Transforms/IndVarSimplify/no-iv-rewrite.ll b/test/Transforms/IndVarSimplify/no-iv-rewrite.ll
index bfdd000e38e..507f695e67c 100644
--- a/test/Transforms/IndVarSimplify/no-iv-rewrite.ll
+++ b/test/Transforms/IndVarSimplify/no-iv-rewrite.ll
@@ -199,7 +199,6 @@ entry:
 ; back to the loop iv.
 ;
 ; CHECK: loop:
-; CHECK: phi i32
 ; CHECK-NOT: phi
 ; CHECK: exit:
 loop:
-- 
2.34.1