Assume intrinsic handling in globalopt

[nlewycky]

This looks correct, but probably not enough.

The point of assumes is that you need them because you're assuming something you don't know, and which globalopt probably also doesn't know. For instance, that a load from an external is equal to some particular value. Globalopt will stop processing when it sees that load, and never get to the assume.

test/Transforms/GlobalOpt/assume.ll

12

What's up with the personality? Is this needed for the testcase?

[Prazek]

test/Transforms/GlobalOpt/assume.ll

12

ok, got rid of it #copypasting

lib/Transforms/IPO/GlobalOpt.cpp

if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
             } else {
               DEBUG(dbgs() << "Found a global var, but can not treat it as an "
                     "invariant.\n");
             }
           }
           // Continue even if we do nothing.
           ++CurInst;
           continue;
+        } else if (II->getIntrinsicID() == Intrinsic::assume) {
+          DEBUG(dbgs() << "Skipping assume intrinsic.\n");
+          ++CurInst;
+          continue;
         }
 
         DEBUG(dbgs() << "Unknown intrinsic. Can not evaluate.\n");
         return false;
       }
 
       // Resolve function pointers.
       Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));

test/Transforms/GlobalOpt/assume.ll

+; RUN: opt -S -globalopt < %s | FileCheck %s
+
+; CHECK: @tmp = global i32 42
+
[e-mail]_ctors = appending global [1 x { i32, void ()* }] [{ i32, void ()* } { i32 65535, void ()* @_GLOBAL__I_a }]
+@tmp = global i32 0
+
+define i32 @TheAnswerToLifeTheUniverseAndEverything() {
+  ret i32 42
+}
+
+define void @_GLOBAL__I_a() personality i8* undef {
+enter:
+  %tmp1 = call i32 @TheAnswerToLifeTheUniverseAndEverything()
+  store i32 %tmp1, i32* @tmp
+  %cmp = icmp eq i32 %tmp1, 42
+  call void @llvm.assume(i1 %cmp)
+  ret void
+}
+
+declare void @llvm.assume(i1)