[llvm] r307521 - [ArgumentPromotion] Change use of removed argument in llvm.dbg.value to undef

[Mikael Holmen via llvm-commits]

Author: uabelho
Date: Sun Jul  9 23:07:24 2017
New Revision: 307521

URL: http://llvm.org/viewvc/llvm-project?rev=307521&view=rev
Log:
[ArgumentPromotion] Change use of removed argument in llvm.dbg.value to undef

Summary:
This solves PR33641.

When removing a dead argument we must also handle possibly existing calls
to llvm.dbg.value that use the removed argument. Now we change the use
of the otherwise dead argument to an undef for some other pass to cleanup
later.

If the calls are left untouched, they will later on cause errors:
 "function-local metadata used in wrong function"
since the ArgumentPromotion rewrites the code by creating a new function
with the wanted signature, but the metadata is not recreated so the new
function may then erroneously use metadata from the old function.

Reviewers: mstorsjo, rnk, arsenm

Reviewed By: rnk

Subscribers: wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D34874

Added:
    llvm/trunk/test/Transforms/ArgumentPromotion/pr33641_remove_arg_dbgvalue.ll
Modified:
    llvm/trunk/lib/Transforms/IPO/ArgumentPromotion.cpp

Modified: llvm/trunk/lib/Transforms/IPO/ArgumentPromotion.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/ArgumentPromotion.cpp?rev=307521&r1=307520&r2=307521&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/ArgumentPromotion.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/ArgumentPromotion.cpp Sun Jul  9 23:07:24 2017
@@ -124,6 +124,10 @@ doPromotion(Function *F, SmallPtrSetImpl
     } else if (I->use_empty()) {
       // Dead argument (which are always marked as promotable)
       ++NumArgumentsDead;
+
+      // There may be remaining metadata uses of the argument for things like
+      // llvm.dbg.value. Replace them with undef.
+      I->replaceAllUsesWith(UndefValue::get(I->getType()));
     } else {
       // Okay, this is being promoted. This means that the only uses are loads
       // or GEPs which are only used by loads

Added: llvm/trunk/test/Transforms/ArgumentPromotion/pr33641_remove_arg_dbgvalue.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/ArgumentPromotion/pr33641_remove_arg_dbgvalue.ll?rev=307521&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/ArgumentPromotion/pr33641_remove_arg_dbgvalue.ll (added)
+++ llvm/trunk/test/Transforms/ArgumentPromotion/pr33641_remove_arg_dbgvalue.ll Sun Jul  9 23:07:24 2017
@@ -0,0 +1,38 @@
+; RUN: opt -argpromotion -verify -dse -S %s -o - | FileCheck %s
+
+; Fix for PR33641. ArgumentPromotion removed the argument to bar but left the call to
+; dbg.value which still used the removed argument.
+
+%p_t = type i16*
+%fun_t = type void (%p_t)*
+
+define void @foo() {
+  %tmp = alloca %fun_t
+  store %fun_t @bar, %fun_t* %tmp
+  ret void
+}
+
+define internal void @bar(%p_t %p)  {
+  call void @llvm.dbg.value(metadata %p_t %p, i64 0, metadata !4, metadata !5), !dbg !6
+  ret void
+}
+
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1)
+!1 = !DIFile(filename: "test.c", directory: "")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = distinct !DISubprogram(name: "bar", unit: !0)
+!4 = !DILocalVariable(name: "p", scope: !3)
+!5 = !DIExpression()
+!6 = !DILocation(line: 1, column: 1, scope: !3)
+
+; The %p argument should be removed, and the use of it in dbg.value should be
+; changed to undef.
+; CHECK:      define internal void @bar() {
+; CHECK-NEXT:   call void @llvm.dbg.value(metadata i16* undef
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }