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
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303590 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/IR/Module.h b/include/llvm/IR/Module.h
index 3024d9e..5e1f680 100644
--- a/include/llvm/IR/Module.h
+++ b/include/llvm/IR/Module.h
@@ -139,9 +139,12 @@
/// 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
diff --git a/lib/IR/Module.cpp b/lib/IR/Module.cpp
index 12c258d..95673e5 100644
--- a/lib/IR/Module.cpp
+++ b/lib/IR/Module.cpp
@@ -481,7 +481,7 @@
}
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 @@
}
void Module::setPIELevel(PIELevel::Level PL) {
- addModuleFlag(ModFlagBehavior::Error, "PIE Level", PL);
+ addModuleFlag(ModFlagBehavior::Max, "PIE Level", PL);
}
void Module::setProfileSummary(Metadata *M) {
diff --git a/lib/IR/Verifier.cpp b/lib/IR/Verifier.cpp
index 21e8048..ffb9ad2 100644
--- a/lib/IR/Verifier.cpp
+++ b/lib/IR/Verifier.cpp
@@ -1282,6 +1282,13 @@
// 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.
diff --git a/lib/Linker/IRMover.cpp b/lib/Linker/IRMover.cpp
index c0af21a..defad19 100644
--- a/lib/Linker/IRMover.cpp
+++ b/lib/Linker/IRMover.cpp
@@ -1157,6 +1157,11 @@
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 @@
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 @@
}
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));
diff --git a/test/Linker/Inputs/module-flags-pic-2-b.ll b/test/Linker/Inputs/module-flags-pic-2-b.ll
index 0d78caf..f652edd 100644
--- a/test/Linker/Inputs/module-flags-pic-2-b.ll
+++ b/test/Linker/Inputs/module-flags-pic-2-b.ll
@@ -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}
diff --git a/test/Linker/module-flags-pic-2-a.ll b/test/Linker/module-flags-pic-2-a.ll
index e09af6b..8898d72 100644
--- a/test/Linker/module-flags-pic-2-a.ll
+++ b/test/Linker/module-flags-pic-2-a.ll
@@ -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}
diff --git a/test/Verifier/module-flags-1.ll b/test/Verifier/module-flags-1.ll
index 36bcb33..ff82c28 100644
--- a/test/Verifier/module-flags-1.ll
+++ b/test/Verifier/module-flags-1.ll
@@ -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 }
