[PATCH] D80064: [X86] Disable LVI load hardening pass at O0

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: craig.topper, mattdr, sconstab.
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D75936 <https://reviews.llvm.org/D75936> caused a compile-time regression for O0 builds (1.5% for sqlite), because the LVI load hardening pass requires a number of additional analysis passes. While load hardening is only performed if a function attribute is specified, the analysis passes will always be executed.

As it doesn't seem to be possible to only run the analysis passes if necessary, this change disables the LVI load hardening pass entirely at O0, on the assumption that this pass is only relevant for production binaries anyway.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80064

Files:
  lib/Target/X86/X86TargetMachine.cpp
  test/CodeGen/X86/O0-pipeline.ll


Index: test/CodeGen/X86/O0-pipeline.ll
===================================================================
--- test/CodeGen/X86/O0-pipeline.ll
+++ test/CodeGen/X86/O0-pipeline.ll
@@ -55,10 +55,6 @@
 ; CHECK-NEXT:       Fast Register Allocator
 ; CHECK-NEXT:       Bundle Machine CFG Edges
 ; CHECK-NEXT:       X86 FP Stackifier
-; CHECK-NEXT:       MachineDominator Tree Construction
-; CHECK-NEXT:       Machine Natural Loop Construction
-; CHECK-NEXT:       Machine Dominance Frontier Construction
-; CHECK-NEXT:       X86 Load Value Injection (LVI) Load Hardening
 ; CHECK-NEXT:       Fixup Statepoint Caller Saved
 ; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:       Machine Optimization Remark Emitter
Index: lib/Target/X86/X86TargetMachine.cpp
===================================================================
--- lib/Target/X86/X86TargetMachine.cpp
+++ lib/Target/X86/X86TargetMachine.cpp
@@ -497,7 +497,11 @@
 
 void X86PassConfig::addPostRegAlloc() {
   addPass(createX86FloatingPointStackifierPass());
-  addPass(createX86LoadValueInjectionLoadHardeningPass());
+
+  // LVI load hardening requires a number of analysis passes that we do not
+  // want to run at optnone.
+  if (getOptLevel() != CodeGenOpt::None)
+    addPass(createX86LoadValueInjectionLoadHardeningPass());
 }
 
 void X86PassConfig::addPreSched2() { addPass(createX86ExpandPseudoPass()); }


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