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

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 32be3e0cdbfde5fa84025a91a74fdf2e9d14d345..e973cdbf44c80d190234cc605aaeb1b3c993bc79 100644 (file)
--- 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 c1c6c926fd9b636aa46eecd6cbef351869d02d4d..107b7af2c1dcfcb56311c197ecd668059cd725d1 100644 (file)
--- 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)