Add a backend option to warn on a given stack size limit.

Option: -mllvm -warn-stack-size=<limit>
Output (if limit is exceeded):
warning: Stack size limit exceeded (<actual size>) in <functionName>.

The longer term plan is to hook that to a clang warning.
PR:4072
<rdar://problem/13987214>

llvm-svn: 183552

1 files changed, 24 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/X86/warn-stack.ll b/llvm/test/CodeGen/X86/warn-stack.ll
new file mode 100644
index 00000000000..0a6a506c7a6
--- /dev/null
+++ b/llvm/test/CodeGen/X86/warn-stack.ll
@@ -0,0 +1,24 @@
+; RUN: llc -march x86 -warn-stack-size=80 < %s 2>&1 >/dev/null | FileCheck %s
+; Check the internal option that warns when the stack size exceeds the
+; given amount.
+; <rdar://13987214>
+
+; CHECK-NOT: nowarn
+define void @nowarn() nounwind ssp {
+entry:
+  %buffer = alloca [12 x i8], align 1
+  %arraydecay = getelementptr inbounds [12 x i8]* %buffer, i64 0, i64 0
+  call void @doit(i8* %arraydecay) nounwind
+  ret void
+}
+
+; CHECK: warning: Stack size limit exceeded (92) in warn.
+define void @warn() nounwind ssp {
+entry:
+  %buffer = alloca [80 x i8], align 1
+  %arraydecay = getelementptr inbounds [80 x i8]* %buffer, i64 0, i64 0
+  call void @doit(i8* %arraydecay) nounwind
+  ret void
+}
+
+declare void @doit(i8*)