[CaptureTracking] Support operand bundles conservatively

[sanjoy]

Summary

Earlier CaptureTracking would assume all "interesting" operands to a
call or invoke were its arguments. With operand bundles this is no
longer true.

Note: an earlier change got doesNotCapture working correctly with
operand bundles.

This change uses DSE to test the changes to CaptureTracking. DSE is a
vehicle for testing only, and is not directly involved in this change.

[sanjoy]

• rebase over changes to dependencies

[reames]

lib/Analysis/CaptureTracking.cpp

256 ↗

(On Diff #39150)

arg_iterator is somewhat the wrong name for the iterator now.

[sanjoy]

• rebase over changes to dependencies

[sanjoy]

• use data_operand_iterator instead of arg_iterator

[reames]

LGTM

llvm/trunk/lib/Analysis/CaptureTracking.cpp

case Instruction::Invoke: {
 
       // Not captured if only passed via 'nocapture' arguments.  Note that
       // calling a function pointer does not in itself cause the pointer to
       // be captured.  This is a subtle point considering that (for example)
       // the callee might return its own address.  It is analogous to saying
       // that loading a value from a pointer does not cause the pointer to be
       // captured, even though the loaded value might be the pointer itself
       // (think of self-referential objects).
-      CallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
-      for (CallSite::arg_iterator A = B; A != E; ++A)
+      CallSite::data_operand_iterator B =
+        CS.data_operands_begin(), E = CS.data_operands_end();
+      for (CallSite::data_operand_iterator A = B; A != E; ++A)
         if (A->get() == V && !CS.doesNotCapture(A - B))
           // The parameter is not marked 'nocapture' - captured.
           if (Tracker->captured(U))
             return;
       break;
     }
     case Instruction::Load:
       // Loading from a pointer does not cause it to be captured.

llvm/trunk/test/Feature/OperandBundles/dse.ll

+; RUN: opt -S -dse < %s | FileCheck %s
+
+declare void @f()
+declare noalias i8* @malloc(i32) nounwind
+
+define void @test_0() {
+; CHECK-LABEL: @test_0(
+  %m = call i8* @malloc(i32 24)
+  tail call void @f() [ "unknown"(i8* %m) ]
+; CHECK: store i8 -19, i8* %m
+  store i8 -19, i8* %m
+  ret void
+}
+
+define i8* @test_1() {
+; CHECK-LABEL: @test_1(
+  %m = call i8* @malloc(i32 24)
+  tail call void @f() [ "unknown"(i8* %m) ]
+  store i8 -19, i8* %m
+  tail call void @f()
+  store i8 101, i8* %m
+
+; CHECK: tail call void @f() [ "unknown"(i8* %m) ]
+; CHECK: store i8 -19, i8* %m
+; CHECK: tail call void @f()
+; CHECK: store i8 101, i8* %m
+
+  ret i8* %m
+}