Merge rust-lang#72

72: A couple of misc bits in ykllvm r=ltratt a=vext01



Co-authored-by: Edd Barrett <vext01@gmail.com>

Author: bors[bot]

llvm/lib/Transforms/Yk/LivenessAnalysis.cpp

@@ -119,13 +119,14 @@ LivenessAnalysis::LivenessAnalysis(Function *Func) {
     }
   }
 
-  // A function implicitly defines its arguments.
-  //
-  // To propagate the arguments properly we pretend that the first instruction
-  // in the entry block defines the arguments.
+  // Normally the live range of a variable starts at the instruction that
+  // defines it. No instruction defines the function's arguments, but it is
+  // important that we don't report them dead. We make function arguments live
+  // at the start of the function by adding them into the `In` set of the first
+  // instruction.
   Instruction *FirstInst = &*Func->getEntryBlock().begin();
   for (auto &Arg : Func->args())
-    Defs[FirstInst].insert(&Arg);
+    In[FirstInst].insert(&Arg);
 
   // Compute the live sets for each instruction.
   //

llvm/lib/Transforms/Yk/StackMaps.cpp

@@ -52,7 +52,7 @@ class YkStackmaps : public ModulePass {
       if (F.empty()) // skip declarations.
         continue;
       LivenessAnalysis LA(&F);
-      for (BasicBlock &BB : F)
+      for (BasicBlock &BB : F) {
         for (Instruction &I : BB) {
           if (isa<CallInst>(I)) {
             CallInst &CI = cast<CallInst>(I);
@@ -78,6 +78,7 @@ class YkStackmaps : public ModulePass {
             SMCalls.insert({&I, LA.getLiveVarsBefore(&I)});
           }
         }
+      }
     }
 
     Function *SMFunc = Intrinsic::getDeclaration(&M, SMFuncID);