[llvm] r303590 - Support for taking the max of module flags when linking, use for PIE/PIC
Teresa Johnson via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 8 07:15:41 PDT 2017
Hi Steven,
Sorry about that. I'm out on vacation for another week, do you want to send
a patch to fix in the meantime?
Teresa
On Mon, Aug 7, 2017 at 10:16 AM, Steven Wu <stevenwu at apple.com> wrote:
> Hi Teresa
>
> I think this commit introduces bitcode compatibility issue. Here is the
> situation:
> If I need to link a bitcode static library into my project. The library is
> built with old compiler which has PIC module flag:
> !0 = !{i32 1, !"PIC Level", i32 2}
> The LTO object I built with latest compiler will have:
> !0 = !{i32 7, !"PIC Level", i32 2}
> When linking, libLTO will error: linking module flags 'PIC Level': IDs
> have conflicting behaviors
>
> My suggestion will be add AutoUpgrade to upgrade PIC Level from old
> bitcode to Module::Max. This should be cleaner than a hack in the IRMover
> to create an exception for this case.
>
> Also, LangRef need to updated to add the new behavior.
>
> Steven
>
> > On May 22, 2017, at 5:08 PM, Teresa Johnson via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
> >
> > Author: tejohnson
> > Date: Mon May 22 19:08:00 2017
> > New Revision: 303590
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=303590&view=rev
> > Log:
> > Support for taking the max of module flags when linking, use for PIE/PIC
> >
> > Summary:
> > Add Max ModFlagBehavior, which can be used to take the max of two
> > module flag values when merging modules. Use it for the PIE and PIC
> > levels.
> >
> > This avoids an error when we try to import from a module built -fpic
> > into a module built -fPIC, for example. For both PIE and PIC levels,
> > this will be legal, since the code generation gets more conservative
> > as the level is increased. Therefore we can take the max instead of
> > somehow trying to block importing between modules compiled with
> > different levels.
> >
> > Reviewers: tmsriram, pcc
> >
> > Subscribers: llvm-commits
> >
> > Differential Revision: https://reviews.llvm.org/D33418
> >
> > Modified:
> > llvm/trunk/include/llvm/IR/Module.h
> > llvm/trunk/lib/IR/Module.cpp
> > llvm/trunk/lib/IR/Verifier.cpp
> > llvm/trunk/lib/Linker/IRMover.cpp
> > llvm/trunk/test/Linker/Inputs/module-flags-pic-2-b.ll
> > llvm/trunk/test/Linker/module-flags-pic-2-a.ll
> > llvm/trunk/test/Verifier/module-flags-1.ll
> >
> > Modified: llvm/trunk/include/llvm/IR/Module.h
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/
> llvm/IR/Module.h?rev=303590&r1=303589&r2=303590&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/include/llvm/IR/Module.h (original)
> > +++ llvm/trunk/include/llvm/IR/Module.h Mon May 22 19:08:00 2017
> > @@ -139,9 +139,12 @@ public:
> > /// during the append operation.
> > AppendUnique = 6,
> >
> > + /// Takes the max of the two values, which are required to be
> integers.
> > + Max = 7,
> > +
> > // Markers:
> > ModFlagBehaviorFirstVal = Error,
> > - ModFlagBehaviorLastVal = AppendUnique
> > + ModFlagBehaviorLastVal = Max
> > };
> >
> > /// Checks if Metadata represents a valid ModFlagBehavior, and stores
> the
> >
> > Modified: llvm/trunk/lib/IR/Module.cpp
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/
> Module.cpp?rev=303590&r1=303589&r2=303590&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/lib/IR/Module.cpp (original)
> > +++ llvm/trunk/lib/IR/Module.cpp Mon May 22 19:08:00 2017
> > @@ -481,7 +481,7 @@ PICLevel::Level Module::getPICLevel() co
> > }
> >
> > void Module::setPICLevel(PICLevel::Level PL) {
> > - addModuleFlag(ModFlagBehavior::Error, "PIC Level", PL);
> > + addModuleFlag(ModFlagBehavior::Max, "PIC Level", PL);
> > }
> >
> > PIELevel::Level Module::getPIELevel() const {
> > @@ -495,7 +495,7 @@ PIELevel::Level Module::getPIELevel() co
> > }
> >
> > void Module::setPIELevel(PIELevel::Level PL) {
> > - addModuleFlag(ModFlagBehavior::Error, "PIE Level", PL);
> > + addModuleFlag(ModFlagBehavior::Max, "PIE Level", PL);
> > }
> >
> > void Module::setProfileSummary(Metadata *M) {
> >
> > Modified: llvm/trunk/lib/IR/Verifier.cpp
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/
> Verifier.cpp?rev=303590&r1=303589&r2=303590&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/lib/IR/Verifier.cpp (original)
> > +++ llvm/trunk/lib/IR/Verifier.cpp Mon May 22 19:08:00 2017
> > @@ -1282,6 +1282,13 @@ Verifier::visitModuleFlag(const MDNode *
> > // These behavior types accept any value.
> > break;
> >
> > + case Module::Max: {
> > + Assert(mdconst::dyn_extract_or_null<ConstantInt>(Op->
> getOperand(2)),
> > + "invalid value for 'max' module flag (expected constant
> integer)",
> > + Op->getOperand(2));
> > + break;
> > + }
> > +
> > case Module::Require: {
> > // The value should itself be an MDNode with two operands, a flag ID
> (an
> > // MDString), and a value.
> >
> > Modified: llvm/trunk/lib/Linker/IRMover.cpp
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Linker/
> IRMover.cpp?rev=303590&r1=303589&r2=303590&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/lib/Linker/IRMover.cpp (original)
> > +++ llvm/trunk/lib/Linker/IRMover.cpp Mon May 22 19:08:00 2017
> > @@ -1157,6 +1157,11 @@ Error IRLinker::linkModuleFlagsMetadata(
> > mdconst::extract<ConstantInt>(DstOp->getOperand(0));
> > unsigned DstBehaviorValue = DstBehavior->getZExtValue();
> >
> > + auto overrideDstValue = [&]() {
> > + DstModFlags->setOperand(DstIndex, SrcOp);
> > + Flags[ID].first = SrcOp;
> > + };
> > +
> > // If either flag has override behavior, handle it first.
> > if (DstBehaviorValue == Module::Override) {
> > // Diagnose inconsistent flags which both have override behavior.
> > @@ -1167,8 +1172,7 @@ Error IRLinker::linkModuleFlagsMetadata(
> > continue;
> > } else if (SrcBehaviorValue == Module::Override) {
> > // Update the destination flag to that of the source.
> > - DstModFlags->setOperand(DstIndex, SrcOp);
> > - Flags[ID].first = SrcOp;
> > + overrideDstValue();
> > continue;
> > }
> >
> > @@ -1204,6 +1208,15 @@ Error IRLinker::linkModuleFlagsMetadata(
> > }
> > continue;
> > }
> > + case Module::Max: {
> > + ConstantInt *DstValue =
> > + mdconst::extract<ConstantInt>(DstOp->getOperand(2));
> > + ConstantInt *SrcValue =
> > + mdconst::extract<ConstantInt>(SrcOp->getOperand(2));
> > + if (SrcValue->getZExtValue() > DstValue->getZExtValue())
> > + overrideDstValue();
> > + break;
> > + }
> > case Module::Append: {
> > MDNode *DstValue = cast<MDNode>(DstOp->getOperand(2));
> > MDNode *SrcValue = cast<MDNode>(SrcOp->getOperand(2));
> >
> > Modified: llvm/trunk/test/Linker/Inputs/module-flags-pic-2-b.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Linker/Inputs/module-flags-pic-2-b.ll?rev=303590&r1=
> 303589&r2=303590&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/test/Linker/Inputs/module-flags-pic-2-b.ll (original)
> > +++ llvm/trunk/test/Linker/Inputs/module-flags-pic-2-b.ll Mon May 22
> 19:08:00 2017
> > @@ -1,3 +1,4 @@
> > -!0 = !{ i32 1, !"PIC Level", i32 2 }
> > +!0 = !{ i32 7, !"PIC Level", i32 2 }
> > +!1 = !{ i32 7, !"PIE Level", i32 2 }
> >
> > -!llvm.module.flags = !{!0}
> > +!llvm.module.flags = !{!0, !1}
> >
> > Modified: llvm/trunk/test/Linker/module-flags-pic-2-a.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Linker/module-flags-pic-2-a.ll?rev=303590&r1=303589&r2=303590&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/test/Linker/module-flags-pic-2-a.ll (original)
> > +++ llvm/trunk/test/Linker/module-flags-pic-2-a.ll Mon May 22 19:08:00
> 2017
> > @@ -1,10 +1,11 @@
> > -; RUN: not llvm-link %s %p/Inputs/module-flags-pic-2-b.ll -S -o - 2> %t
> > -; RUN: FileCheck --check-prefix=CHECK-ERRORS < %t %s
> > +; RUN: llvm-link %s %p/Inputs/module-flags-pic-2-b.ll -S -o - |
> FileCheck %s
> >
> > -; test linking modules with two different PIC levels
> > +; test linking modules with two different PIC and PIE levels
> >
> > -!0 = !{ i32 1, !"PIC Level", i32 1 }
> > +!0 = !{ i32 7, !"PIC Level", i32 1 }
> > +!1 = !{ i32 7, !"PIE Level", i32 1 }
> >
> > -!llvm.module.flags = !{!0}
> > +!llvm.module.flags = !{!0, !1}
> >
> > -; CHECK-ERRORS: ERROR: linking module flags 'PIC Level': IDs have
> conflicting values
> > +; CHECK: !0 = !{i32 7, !"PIC Level", i32 2}
> > +; CHECK: !1 = !{i32 7, !"PIE Level", i32 2}
> >
> > Modified: llvm/trunk/test/Verifier/module-flags-1.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Verifier/module-flags-1.ll?rev=303590&r1=303589&r2=303590&view=diff
> > ============================================================
> ==================
> > --- llvm/trunk/test/Verifier/module-flags-1.ll (original)
> > +++ llvm/trunk/test/Verifier/module-flags-1.ll Mon May 22 19:08:00 2017
> > @@ -41,6 +41,10 @@
> > ; CHECK-NOT: invalid value for 'append'-type module flag (expected a
> metadata node)
> > !18 = !{i32 5, !"flag-4", !{i32 57}}
> >
> > +; Check that any 'max' module flags are valid.
> > +; CHECK: invalid value for 'max' module flag (expected constant integer)
> > +!19 = !{i32 7, !"max", !"max"}
> > +
> > ; Check that any 'require' module flags are valid.
> > ; CHECK: invalid requirement on flag, flag is not present in module
> > !11 = !{i32 3, !"bar", !{!"no-such-flag", i32 52}}
> > @@ -54,4 +58,4 @@
> >
> > !llvm.module.flags = !{
> > !0, !1, !2, !3, !4, !5, !6, !7, !8, !9, !10, !11, !12, !13, !14, !15,
> > - !16, !17, !18 }
> > + !16, !17, !18, !19 }
> >
> >
> > _______________________________________________
> > llvm-commits mailing list
> > llvm-commits at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>
>
--
Teresa Johnson | Software Engineer | tejohnson at google.com | 408-460-2413
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