[PM] Introduce an analysis set used to preserve all analyses over

a function's CFG when that CFG is unchanged.

This allows transformation passes to simply claim they preserve the CFG
and analysis passes to check for the CFG being preserved to remove the
fanout of all analyses being listed in all passes.

I've gone through and removed or cleaned up as many of the comments
reminding us to do this as I could.

Differential Revision: https://reviews.llvm.org/D28627

llvm-svn: 292054

3 files changed, 8 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Utils/LCSSA.cpp b/llvm/lib/Transforms/Utils/LCSSA.cpp
index 68c6b74d5e5..2671840a8bb 100644
--- a/llvm/lib/Transforms/Utils/LCSSA.cpp
+++ b/llvm/lib/Transforms/Utils/LCSSA.cpp
@@ -395,8 +395,8 @@ PreservedAnalyses LCSSAPass::run(Function &F, FunctionAnalysisManager &AM) {
   if (!formLCSSAOnAllLoops(&LI, DT, SE))
     return PreservedAnalyses::all();
 
-  // FIXME: This should also 'preserve the CFG'.
   PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
   PA.preserve<BasicAA>();
   PA.preserve<GlobalsAA>();
   PA.preserve<SCEVAA>();
diff --git a/llvm/lib/Transforms/Utils/Mem2Reg.cpp b/llvm/lib/Transforms/Utils/Mem2Reg.cpp
index 24b3b12930a..4984c3cc2a7 100644
--- a/llvm/lib/Transforms/Utils/Mem2Reg.cpp
+++ b/llvm/lib/Transforms/Utils/Mem2Reg.cpp
@@ -59,8 +59,9 @@ PreservedAnalyses PromotePass::run(Function &F, FunctionAnalysisManager &AM) {
   if (!promoteMemoryToRegister(F, DT, AC))
     return PreservedAnalyses::all();
 
-  // FIXME: This should also 'preserve the CFG'.
-  return PreservedAnalyses::none();
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  return PA;
 }
 
 namespace {
diff --git a/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp b/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp
index 1220490123c..432a2c5479b 100644
--- a/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyInstructions.cpp
@@ -136,6 +136,8 @@ PreservedAnalyses InstSimplifierPass::run(Function &F,
   bool Changed = runImpl(F, &DT, &TLI, &AC);
   if (!Changed)
     return PreservedAnalyses::all();
-  // FIXME: This should also 'preserve the CFG'.
-  return PreservedAnalyses::none();
+
+  PreservedAnalyses PA;
+  PA.preserveSet<CFGAnalyses>();
+  return PA;
 }