When analyzing params/args for readnone/readonly, don't forget to consider that a pointer argument may be passed through a callsite to the return, and that we may need to analyze it. Fixes a bug reported on llvm-dev: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-May/073098.html

llvm-svn: 209870

llvm/lib/Transforms/IPO/FunctionAttrs.cpp

@@ -449,14 +449,29 @@ determinePointerReadAttrs(Argument *A,
 
     case Instruction::Call:
     case Instruction::Invoke: {
+      bool Captures = true;
+
+      if (I->getType()->isVoidTy())
+        Captures = false;
+
+      auto AddUsersToWorklistIfCapturing = [&] {
+        if (Captures)
+          for (Use &UU : I->uses())
+            if (Visited.insert(&UU))
+              Worklist.push_back(&UU);
+      };
+
       CallSite CS(I);
-      if (CS.doesNotAccessMemory())
+      if (CS.doesNotAccessMemory()) {
+        AddUsersToWorklistIfCapturing();
         continue;
+      }
 
       Function *F = CS.getCalledFunction();
       if (!F) {
         if (CS.onlyReadsMemory()) {
           IsRead = true;
+          AddUsersToWorklistIfCapturing();
           continue;
         }
         return Attribute::None;
@@ -471,6 +486,7 @@ determinePointerReadAttrs(Argument *A,
                    "More params than args in non-varargs call.");
             return Attribute::None;
           }
+          Captures &= !CS.doesNotCapture(A - B);
           if (SCCNodes.count(AI))
             continue;
           if (!CS.onlyReadsMemory() && !CS.onlyReadsMemory(A - B))
@@ -479,6 +495,7 @@ determinePointerReadAttrs(Argument *A,
             IsRead = true;
         }
       }
+      AddUsersToWorklistIfCapturing();
       break;
     }
 

llvm/test/Transforms/FunctionAttrs/nocapture.ll

@@ -68,7 +68,7 @@ define i1* @lookup_bit(i32* %q, i32 %bitno) readnone nounwind {
 	ret i1* %lookup
 }
 
-; CHECK: define i1 @c7(i32* readnone %q, i32 %bitno)
+; CHECK: define i1 @c7(i32* readonly %q, i32 %bitno)
 define i1 @c7(i32* %q, i32 %bitno) {
 	%ptr = call i1* @lookup_bit(i32* %q, i32 %bitno)
 	%val = load i1* %ptr

llvm/test/Transforms/FunctionAttrs/readattrs.ll

@@ -51,3 +51,17 @@ define void @test6_2(i8** %p, i8* %q) {
 define void @test7_1(i32* inalloca %a) {
   ret void
 }
+
+; CHECK: define i32* @test8_1(i32* readnone %p)
+define i32* @test8_1(i32* %p) {
+entry:
+  ret i32* %p
+}
+
+; CHECK: define void @test8_2(i32* %p)
+define void @test8_2(i32* %p) {
+entry:
+  %call = call i32* @test8_1(i32* %p)
+  store i32 10, i32* %call, align 4
+  ret void
+}