llvm-D38765-gvn_5.0.patch
From c65eb3a4b70a119da41ff2d3ebce0b037f92cba7 Mon Sep 17 00:00:00 2001
From: Davide Italiano <davide@freebsd.org>
Date: Wed, 11 Oct 2017 04:21:51 +0000
Subject: [PATCH] [GVN] Don't replace constants with constants.
This fixes PR34908. Patch by Alex Crichton!
Differential Revision: https://reviews.llvm.org/D38765
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315429 91177308-0d34-0410-b5e6-96231b3b80d8
---
lib/Transforms/Scalar/GVN.cpp | 5 +++++
test/Transforms/GVN/pr34908.ll | 13 +++++++++++++
2 files changed, 18 insertions(+)
create mode 100644 test/Transforms/GVN/pr34908.ll
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index 4e24d755c26..c3cc2375e3b 100644
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -1362,6 +1362,11 @@ bool GVN::processAssumeIntrinsic(IntrinsicInst *IntrinsicI) {
}
markInstructionForDeletion(IntrinsicI);
return false;
+ } else if (isa<Constant>(V)) {
+ // If it's not false, and constant, it must evaluate to true. This means our
+ // assume is assume(true), and thus, pointless, and we don't want to do
+ // anything more here.
+ return false;
}
Constant *True = ConstantInt::getTrue(V->getContext());
diff --git a/test/Transforms/GVN/pr34908.ll b/test/Transforms/GVN/pr34908.ll
new file mode 100644
index 00000000000..c2b58ad34a6
--- /dev/null
+++ b/test/Transforms/GVN/pr34908.ll
@@ -0,0 +1,13 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -gvn -S | FileCheck %s
+
+define i1 @foo() {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT: call void @llvm.assume(i1 undef)
+; CHECK-NEXT: ret i1 undef
+;
+ call void @llvm.assume(i1 undef)
+ ret i1 undef
+}
+
+declare void @llvm.assume(i1)