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
llvm-svn: 303590
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 21e8048..ffb9ad2 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/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.