PMB: Add an importing WPD pass to the start of the ThinLTO backend pipeline.
Differential Revision: https://reviews.llvm.org/D30008
llvm-svn: 295260
diff --git a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
index bfc6bbd..1913b50 100644
--- a/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -830,8 +830,22 @@
if (VerifyInput)
PM.add(createVerifierPass());
- if (Summary)
+ if (Summary) {
+ // These passes import type identifier resolutions for whole-program
+ // devirtualization and CFI. They must run early because other passes may
+ // disturb the specific instruction patterns that these passes look for,
+ // creating dependencies on resolutions that may not appear in the summary.
+ //
+ // For example, GVN may transform the pattern assume(type.test) appearing in
+ // two basic blocks into assume(phi(type.test, type.test)), which would
+ // transform a dependency on a WPD resolution into a dependency on a type
+ // identifier resolution for CFI.
+ //
+ // Also, WPD has access to more precise information than ICP and can
+ // devirtualize more effectively, so it should operate on the IR first.
+ PM.add(createWholeProgramDevirtPass(PassSummaryAction::Import, Summary));
PM.add(createLowerTypeTestsPass(PassSummaryAction::Import, Summary));
+ }
populateModulePassManager(PM);