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Support for taking the max of module flags when linking, use for PIE/PIC

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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
This commit is contained in:
Teresa Johnson
2017-05-23 00:08:00 +00:00
parent 0c7d4d7e21
commit 2db1369c1f
7 changed files with 43 additions and 14 deletions
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4
llvm/lib/IR/Module.cpp
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@@ -481,7 +481,7 @@ PICLevel::Level Module::getPICLevel() const {
}
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() const {
}
void Module::setPIELevel(PIELevel::Level PL) {
addModuleFlag(ModFlagBehavior::Error, "PIE Level", PL);
addModuleFlag(ModFlagBehavior::Max, "PIE Level", PL);
}
void Module::setProfileSummary(Metadata *M) {