Add a test for r307754

As promised in D35003.

Uses -codegenprepare instead of -instcombine since we hit the same
buggy path anyway, and CGP lets us keep this test really simple
(instcombine likes turning the alloca T, N into alloca [N x T], which
hides the bug this is testing for).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307811 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/test/Transforms/CodeGenPrepare/crash-on-large-allocas.ll b/test/Transforms/CodeGenPrepare/crash-on-large-allocas.ll
new file mode 100644 (file)
index 0000000..3808c0e
--- /dev/null
+++ b/test/Transforms/CodeGenPrepare/crash-on-large-allocas.ll
@@ -0,0 +1,16 @@
+; RUN: opt -S -codegenprepare %s -o - | FileCheck %s
+;
+; Ensure that we don't {crash,return a bad value} when given an alloca larger
+; than what a pointer can represent.
+
+target datalayout = "p:16:16"
+
+; CHECK-LABEL: @alloca_overflow_is_unknown(
+define i16 @alloca_overflow_is_unknown() {
+  %i = alloca i8, i32 65537
+  %j = call i16 @llvm.objectsize.i16.p0i8(i8* %i, i1 false, i1 false)
+  ; CHECK: ret i16 -1
+  ret i16 %j
+}
+
+declare i16 @llvm.objectsize.i16.p0i8(i8*, i1, i1)