[PATCH] D75201: [ThinLTO/LowerTypeTests] Handle unpromoted local type ids

[Teresa Johnson via Phabricator via llvm-commits]

tejohnson created this revision.
tejohnson added reviewers: evgeny777, pcc.
Herald added subscribers: dexonsmith, steven_wu, hiraditya, inglorion.
Herald added a project: LLVM.

Fixes an issue that cropped up after the changes in D73242 <https://reviews.llvm.org/D73242> to delay
the lowering of type tests. LTT couldn't handle any type tests with
non-string type id (which happens for local vtables, which we try to
promote during the compile step but cannot always when there are no
exported symbols).

We can simply treat the same as having an Unknown resolution, which
delays their lowering, still allowing such type tests to be used in
subsequent optimization (e.g. planned usage during ICP). The final
lowering which simply removes these handles them fine.

Beefed up an existing ThinLTO test for such unpromoted type ids so that
the internal vtable isn't removed before lower type tests, which hides
the problem.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75201

Files:
  llvm/lib/Transforms/IPO/LowerTypeTests.cpp
  llvm/test/ThinLTO/X86/nodevirt-nonpromoted-typeid.ll


Index: llvm/test/ThinLTO/X86/nodevirt-nonpromoted-typeid.ll
===================================================================
--- llvm/test/ThinLTO/X86/nodevirt-nonpromoted-typeid.ll
+++ llvm/test/ThinLTO/X86/nodevirt-nonpromoted-typeid.ll
@@ -33,6 +33,8 @@
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-grtev4-linux-gnu"
 
+ at llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @g, i8* null }]
+
 %struct.D = type { i32 (...)** }
 
 @_ZTV1D = internal constant { [3 x i8*] } { [3 x i8*] [i8* null, i8* undef, i8* bitcast (i32 (%struct.D*, i32)* @_ZN1D1mEi to i8*)] }, !type !3
@@ -57,6 +59,23 @@
 ; CHECK-IR-LABEL: ret i32
 ; CHECK-IR-LABEL: }
 
+; Function Attrs: inlinehint nounwind uwtable
+define internal void @_ZN1DC2Ev(%struct.D* %this) unnamed_addr align 2 {
+entry:
+  %this.addr = alloca %struct.D*, align 8
+  store %struct.D* %this, %struct.D** %this.addr, align 8
+  %this1 = load %struct.D*, %struct.D** %this.addr
+  %0 = bitcast %struct.D* %this1 to i32 (...)***
+  store i32 (...)** bitcast (i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV1D, i64 0, inrange i32 0, i64 2) to i32 (...)**), i32 (...)*** %0, align 8
+  ret void
+}
+
+define internal void @g() section ".text.startup" {
+  %d = alloca %struct.D, align 8
+  call void @_ZN1DC2Ev(%struct.D* %d)
+  ret void
+}
+
 declare i1 @llvm.type.test(i8*, metadata)
 declare void @llvm.assume(i1)
 
Index: llvm/lib/Transforms/IPO/LowerTypeTests.cpp
===================================================================
--- llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -1040,9 +1040,11 @@
     report_fatal_error("Second argument of llvm.type.test must be metadata");
 
   auto TypeIdStr = dyn_cast<MDString>(TypeIdMDVal->getMetadata());
+  // If this is a local unpromoted type, which doesn't have a metadata string,
+  // treat as Unknown and delay lowering, so that we can still utilize it for
+  // later optimizations.
   if (!TypeIdStr)
-    report_fatal_error(
-        "Second argument of llvm.type.test must be a metadata string");
+    return;
 
   TypeIdLowering TIL = importTypeId(TypeIdStr->getString());
   Value *Lowered = lowerTypeTestCall(TypeIdStr, CI, TIL);


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D75201.246797.patch
Type: text/x-patch
Size: 2342 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200226/0e015657/attachment.bin>