From 3f2ffe0423fdf58e2f07e32a27089c68011d4125 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Fri, 7 Nov 2014 08:54:19 +0000
Subject: [PATCH] SCCP: overdefined calls cannot become constant

We would attempt to fold away a call instruction which had been marked
overdefined.  However, it's not valid to transition to constant from
overdefined.

This fixes PR21512.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221513 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/SCCP.cpp       |  3 +++
 test/Transforms/SCCP/ipsccp-basic.ll | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 32be3e0cdbf..e973cdbf44c 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -1107,6 +1107,9 @@ CallOverdefined:
         Operands.push_back(State.getConstant());
       }
 
+      if (getValueState(I).isOverdefined())
+        return;
+
       // If we can constant fold this, mark the result of the call as a
       // constant.
       if (Constant *C = ConstantFoldCall(F, Operands, TLI))
diff --git a/test/Transforms/SCCP/ipsccp-basic.ll b/test/Transforms/SCCP/ipsccp-basic.ll
index c1c6c926fd9..107b7af2c1d 100644
--- a/test/Transforms/SCCP/ipsccp-basic.ll
+++ b/test/Transforms/SCCP/ipsccp-basic.ll
@@ -227,3 +227,23 @@ entry:
 ; CHECK-LABEL: define internal i32 @test10b(
 ; CHECK: ret i32 undef
 }
+
+;;======================== test11
+
+define i64 @test11a() {
+  %xor = xor i64 undef, undef
+  ret i64 %xor
+; CHECK-LABEL: define i64 @test11a
+; CHECK: ret i64 0
+}
+
+define void @test11b() {
+  %call1 = call i64 @test11a()
+  %call2 = call i64 @llvm.ctpop.i64(i64 %call1)
+  ret void
+; CHECK-LABEL: define void @test11b
+; CHECK: %[[call1:.*]] = call i64 @test11a()
+; CHECK: %[[call2:.*]] = call i64 @llvm.ctpop.i64(i64 0)
+}
+
+declare i64 @llvm.ctpop.i64(i64)