[Inliner] Add per-inlining verification.

Previously, there was an -Xllvm option to verify after all inlining to a
particlar caller.  That makes it a chore to track down which apply's
inlining resulted in invalid code.  Here, a new option is added that
verifies after each run of the inliner.

Author: nate-chandler

lib/SILOptimizer/Mandatory/MandatoryInlining.cpp

@@ -50,6 +50,8 @@ extern llvm::cl::opt<bool> SILPrintInliningCallerBefore;
 
 extern llvm::cl::opt<bool> SILPrintInliningCallerAfter;
 
+extern llvm::cl::opt<bool> EnableVerifyAfterEachInlining;
+
 extern void printInliningDetailsCallee(StringRef passName, SILFunction *caller,
                                        SILFunction *callee);
 
@@ -972,6 +974,16 @@ runOnFunctionRecursively(SILOptFunctionBuilder &FuncBuilder, SILFunction *F,
       // later.
       changedFunctions.insert(F);
 
+      if (EnableVerifyAfterEachInlining) {
+        if (invalidatedStackNesting) {
+          StackNesting::fixNesting(F);
+          changedFunctions.insert(F);
+          invalidatedStackNesting = false;
+        }
+
+        F->verify();
+      }
+
       // Resume inlining within nextBB, which contains only the inlined
       // instructions and possibly instructions in the original call block that
       // have not yet been visited.

lib/SILOptimizer/Transforms/PerformanceInliner.cpp

@@ -63,6 +63,12 @@ llvm::cl::opt<bool> SILPrintInliningCallerAfter(
     llvm::cl::desc(
         "Print functions into which another function has been inlined."));
 
+llvm::cl::opt<bool> EnableVerifyAfterEachInlining(
+    "sil-inline-verify-after-each-inline", llvm::cl::init(false),
+    llvm::cl::desc(
+        "Run sil verification after inlining each found callee apply "
+        "site into a caller."));
+
 //===----------------------------------------------------------------------===//
 //                           Printing Helpers
 //===----------------------------------------------------------------------===//
@@ -1038,6 +1044,20 @@ bool SILPerformanceInliner::inlineCallsIntoFunction(SILFunction *Caller) {
     if (SILPrintInliningCallerAfter) {
       printInliningDetailsCallerAfter(PassName, Caller, Callee);
     }
+    if (EnableVerifyAfterEachInlining) {
+      deleter.cleanupDeadInstructions();
+
+      // The inliner splits blocks at call sites. Re-merge trivial branches to
+      // reestablish a canonical CFG.
+      mergeBasicBlocks(Caller);
+
+      if (invalidatedStackNesting) {
+        StackNesting::fixNesting(Caller);
+        invalidatedStackNesting = false;
+      }
+
+      Caller->verify();
+    }
   }
   deleter.cleanupDeadInstructions();