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, 13 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/PrologEpilogInserter.cpp b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
index 959dd7df58e..3a77af0cc49 100644
--- a/llvm/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/llvm/lib/CodeGen/PrologEpilogInserter.cpp
@@ -35,6 +35,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetFrameLowering.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetMachine.h"
@@ -46,6 +47,11 @@ using namespace llvm;
 char PEI::ID = 0;
 char &llvm::PrologEpilogCodeInserterID = PEI::ID;
 
+static cl::opt<uint64_t>
+WarnStackSize("warn-stack-size", cl::Hidden,
+              cl::desc("Warn for stack size bigger than the given"
+                       " number"));
+
 INITIALIZE_PASS_BEGIN(PEI, "prologepilog",
                 "Prologue/Epilogue Insertion", false, false)
 INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
@@ -128,6 +134,13 @@ bool PEI::runOnMachineFunction(MachineFunction &Fn) {
   // Clear any vregs created by virtual scavenging.
   Fn.getRegInfo().clearVirtRegs();
 
+  // Warn on stack size when we exceeds the given limit.
+  MachineFrameInfo *MFI = Fn.getFrameInfo();
+  if (WarnStackSize.getNumOccurrences() > 0 &&
+      WarnStackSize < MFI->getStackSize())
+    errs() << "warning: Stack size limit exceeded (" << MFI->getStackSize()
+           << ") in " << Fn.getName()  << ".\n";
+
   delete RS;
   clearAllSets();
   return true;