[llvm] 3fa231f - Add SimplifyTypeTests pass.
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llvm-commits at lists.llvm.org
Thu Jun 5 11:09:24 PDT 2025
Author: Peter Collingbourne
Date: 2025-06-05T11:09:20-07:00
New Revision: 3fa231f47c584005981f49294e07801f90a35bfe
URL: https://github.com/llvm/llvm-project/commit/3fa231f47c584005981f49294e07801f90a35bfe
DIFF: https://github.com/llvm/llvm-project/commit/3fa231f47c584005981f49294e07801f90a35bfe.diff
LOG: Add SimplifyTypeTests pass.
This pass figures out whether inlining has exposed a constant address to
a lowered type test, and remove the test if so and the address is known
to pass the test. Unfortunately this pass ends up needing to reverse
engineer what LowerTypeTests did; this is currently inherent to the design
of ThinLTO importing where LowerTypeTests needs to run at the start.
Reviewers: teresajohnson
Reviewed By: teresajohnson
Pull Request: https://github.com/llvm/llvm-project/pull/141327
Added:
llvm/test/Transforms/SimplifyTypeTests/basic.ll
Modified:
llvm/include/llvm/Transforms/IPO/LowerTypeTests.h
llvm/lib/Passes/PassBuilderPipelines.cpp
llvm/lib/Passes/PassRegistry.def
llvm/lib/Transforms/IPO/LowerTypeTests.cpp
llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/Transforms/IPO/LowerTypeTests.h b/llvm/include/llvm/Transforms/IPO/LowerTypeTests.h
index 02adcd8bfd45d..40f2d2c4fadf7 100644
--- a/llvm/include/llvm/Transforms/IPO/LowerTypeTests.h
+++ b/llvm/include/llvm/Transforms/IPO/LowerTypeTests.h
@@ -223,6 +223,11 @@ class LowerTypeTestsPass : public PassInfoMixin<LowerTypeTestsPass> {
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
};
+class SimplifyTypeTestsPass : public PassInfoMixin<SimplifyTypeTestsPass> {
+public:
+ PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
+};
+
} // end namespace llvm
#endif // LLVM_TRANSFORMS_IPO_LOWERTYPETESTS_H
diff --git a/llvm/lib/Passes/PassBuilderPipelines.cpp b/llvm/lib/Passes/PassBuilderPipelines.cpp
index 452baf2da5125..a99146d5eaa34 100644
--- a/llvm/lib/Passes/PassBuilderPipelines.cpp
+++ b/llvm/lib/Passes/PassBuilderPipelines.cpp
@@ -1287,6 +1287,9 @@ PassBuilder::buildModuleSimplificationPipeline(OptimizationLevel Level,
// and argument promotion.
MPM.addPass(DeadArgumentEliminationPass());
+ if (Phase == ThinOrFullLTOPhase::ThinLTOPostLink)
+ MPM.addPass(SimplifyTypeTestsPass());
+
if (Phase != ThinOrFullLTOPhase::ThinLTOPreLink)
MPM.addPass(CoroCleanupPass());
diff --git a/llvm/lib/Passes/PassRegistry.def b/llvm/lib/Passes/PassRegistry.def
index fe6f13477bb12..f761d0dab09a8 100644
--- a/llvm/lib/Passes/PassRegistry.def
+++ b/llvm/lib/Passes/PassRegistry.def
@@ -101,6 +101,7 @@ MODULE_PASS("jmc-instrumenter", JMCInstrumenterPass())
MODULE_PASS("lower-emutls", LowerEmuTLSPass())
MODULE_PASS("lower-global-dtors", LowerGlobalDtorsPass())
MODULE_PASS("lower-ifunc", LowerIFuncPass())
+MODULE_PASS("simplify-type-tests", SimplifyTypeTestsPass())
MODULE_PASS("lowertypetests", LowerTypeTestsPass())
MODULE_PASS("fatlto-cleanup", FatLtoCleanup())
MODULE_PASS("pgo-force-function-attrs", PGOForceFunctionAttrsPass(PGOOpt ? PGOOpt->ColdOptType : PGOOptions::ColdFuncOpt::Default))
diff --git a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
index de9efc5b25b4b..d1695a88aa5bc 100644
--- a/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
+++ b/llvm/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -19,11 +19,14 @@
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/TinyPtrVector.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/PostDominators.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/TypeMetadataUtils.h"
#include "llvm/Analysis/ValueTracking.h"
@@ -2472,3 +2475,94 @@ PreservedAnalyses LowerTypeTestsPass::run(Module &M,
return PreservedAnalyses::all();
return PreservedAnalyses::none();
}
+
+PreservedAnalyses SimplifyTypeTestsPass::run(Module &M,
+ ModuleAnalysisManager &AM) {
+ bool Changed = false;
+ // Figure out whether inlining has exposed a constant address to a lowered
+ // type test, and remove the test if so and the address is known to pass the
+ // test. Unfortunately this pass ends up needing to reverse engineer what
+ // LowerTypeTests did; this is currently inherent to the design of ThinLTO
+ // importing where LowerTypeTests needs to run at the start.
+ //
+ // We look for things like:
+ //
+ // sub (i64 ptrtoint (ptr @_Z2fpv to i64), i64 ptrtoint (ptr
+ // @__typeid__ZTSFvvE_global_addr to i64))
+ //
+ // which gets replaced with 0 if _Z2fpv (more specifically _Z2fpv.cfi, the
+ // function referred to by the jump table) is a member of the type _ZTSFvv, as
+ // well as things like
+ //
+ // icmp eq ptr @_Z2fpv, @__typeid__ZTSFvvE_global_addr
+ //
+ // which gets replaced with true if _Z2fpv is a member.
+ for (auto &GV : M.globals()) {
+ if (!GV.getName().starts_with("__typeid_") ||
+ !GV.getName().ends_with("_global_addr"))
+ continue;
+ // __typeid_foo_global_addr -> foo
+ auto *MD = MDString::get(M.getContext(),
+ GV.getName().substr(9, GV.getName().size() - 21));
+ auto MaySimplifyPtr = [&](Value *Ptr) {
+ if (auto *GV = dyn_cast<GlobalValue>(Ptr))
+ if (auto *CFIGV = M.getNamedValue((GV->getName() + ".cfi").str()))
+ Ptr = CFIGV;
+ return isKnownTypeIdMember(MD, M.getDataLayout(), Ptr, 0);
+ };
+ auto MaySimplifyInt = [&](Value *Op) {
+ auto *PtrAsInt = dyn_cast<ConstantExpr>(Op);
+ if (!PtrAsInt || PtrAsInt->getOpcode() != Instruction::PtrToInt)
+ return false;
+ return MaySimplifyPtr(PtrAsInt->getOperand(0));
+ };
+ for (User *U : make_early_inc_range(GV.users())) {
+ if (auto *CI = dyn_cast<ICmpInst>(U)) {
+ if (CI->getPredicate() == CmpInst::ICMP_EQ &&
+ MaySimplifyPtr(CI->getOperand(0))) {
+ // This is an equality comparison (TypeTestResolution::Single case in
+ // lowerTypeTestCall). In this case we just replace the comparison
+ // with true.
+ CI->replaceAllUsesWith(ConstantInt::getTrue(M.getContext()));
+ CI->eraseFromParent();
+ Changed = true;
+ }
+ }
+ auto *CE = dyn_cast<ConstantExpr>(U);
+ if (!CE || CE->getOpcode() != Instruction::PtrToInt)
+ continue;
+ for (Use &U : make_early_inc_range(CE->uses())) {
+ auto *CE = dyn_cast<ConstantExpr>(U.getUser());
+ if (U.getOperandNo() == 1 && CE &&
+ CE->getOpcode() == Instruction::Sub &&
+ MaySimplifyInt(CE->getOperand(0))) {
+ // This is a computation of PtrOffset as generated by
+ // LowerTypeTestsModule::lowerTypeTestCall above. If
+ // isKnownTypeIdMember passes we just pretend it evaluated to 0. This
+ // should cause later passes to remove the range and alignment checks.
+ // The bitset checks won't be removed but those are uncommon.
+ CE->replaceAllUsesWith(ConstantInt::get(CE->getType(), 0));
+ Changed = true;
+ }
+ auto *CI = dyn_cast<ICmpInst>(U.getUser());
+ if (U.getOperandNo() == 1 && CI &&
+ CI->getPredicate() == CmpInst::ICMP_EQ &&
+ MaySimplifyInt(CI->getOperand(0))) {
+ // This is an equality comparison. Unlike in the case above it
+ // remained as an integer compare.
+ CI->replaceAllUsesWith(ConstantInt::getTrue(M.getContext()));
+ CI->eraseFromParent();
+ Changed = true;
+ }
+ }
+ }
+ }
+
+ if (!Changed)
+ return PreservedAnalyses::all();
+ PreservedAnalyses PA = PreservedAnalyses::none();
+ PA.preserve<DominatorTreeAnalysis>();
+ PA.preserve<PostDominatorTreeAnalysis>();
+ PA.preserve<LoopAnalysis>();
+ return PA;
+}
diff --git a/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll b/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
index ed13402e1c4b1..62bb02d9b3c40 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-defaults.ll
@@ -159,6 +159,7 @@
; CHECK-O-NEXT: Invalidating analysis: ShouldNotRunFunctionPassesAnalysis
; CHECK-O-NEXT: Invalidating analysis: InlineAdvisorAnalysis
; CHECK-O-NEXT: Running pass: DeadArgumentEliminationPass
+; CHECK-O-NEXT: Running pass: SimplifyTypeTestsPass
; CHECK-O-NEXT: Running pass: CoroCleanupPass
; CHECK-POSTLINK-O-NEXT: Running pass: GlobalOptPass
; CHECK-POSTLINK-O-NEXT: Running pass: GlobalDCEPass
diff --git a/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll b/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
index c82c34f7ff01e..0da7a9f73bdce 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
@@ -143,6 +143,7 @@
; CHECK-O-NEXT: Invalidating analysis: ShouldNotRunFunctionPassesAnalysis
; CHECK-O-NEXT: Invalidating analysis: InlineAdvisorAnalysis
; CHECK-O-NEXT: Running pass: DeadArgumentEliminationPass
+; CHECK-O-NEXT: Running pass: SimplifyTypeTestsPass
; CHECK-O-NEXT: Running pass: CoroCleanupPass
; CHECK-O-NEXT: Running pass: GlobalOptPass
; CHECK-O-NEXT: Running pass: GlobalDCEPass
diff --git a/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll b/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
index d375747547d61..38b7890682783 100644
--- a/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
+++ b/llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
@@ -152,6 +152,7 @@
; CHECK-O-NEXT: Invalidating analysis: ShouldNotRunFunctionPassesAnalysis
; CHECK-O-NEXT: Invalidating analysis: InlineAdvisorAnalysis
; CHECK-O-NEXT: Running pass: DeadArgumentEliminationPass
+; CHECK-O-NEXT: Running pass: SimplifyTypeTestsPass
; CHECK-O-NEXT: Running pass: CoroCleanupPass
; CHECK-O-NEXT: Running pass: GlobalOptPass
; CHECK-O-NEXT: Running pass: GlobalDCEPass
diff --git a/llvm/test/Transforms/SimplifyTypeTests/basic.ll b/llvm/test/Transforms/SimplifyTypeTests/basic.ll
new file mode 100644
index 0000000000000..8f9dffa2ace98
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyTypeTests/basic.ll
@@ -0,0 +1,46 @@
+; Test that a lowered type test for a type is simplified to true
+; if the target is a constant member of that type.
+
+; RUN: opt -S %s -passes=simplify-type-tests | FileCheck %s
+
+; Test that the simplification does not occur if the type is wrong.
+
+; RUN: sed -e 's/"_ZTSFvvE"/"wrongtype"/g' %s | opt -S -passes=simplify-type-tests | FileCheck --check-prefix=WRONGTYPE %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+ at __typeid__ZTSFvvE_global_addr = external hidden global [0 x i8], code_model "small"
+
+define void @_Z2fpv.cfi() !type !0 {
+ ret void
+}
+
+define i64 @main() {
+ %1 = icmp eq ptr @_Z2fpv, @__typeid__ZTSFvvE_global_addr
+ ; CHECK: br i1 true
+ ; WRONGTYPE: br i1 %
+ br i1 %1, label %3, label %2
+
+2:
+ tail call void @llvm.ubsantrap(i8 2)
+ unreachable
+
+3:
+ ; CHECK: br i1 true
+ ; WRONGTYPE: br i1 %
+ %c = icmp eq i64 ptrtoint (ptr @_Z2fpv to i64), ptrtoint (ptr @__typeid__ZTSFvvE_global_addr to i64)
+ br i1 %c, label %4, label %2
+
+4:
+ tail call void @_Z2fpv()
+ ; CHECK: ret i64 0
+ ; WRONGTYPE: ret i64 sub
+ ret i64 sub (i64 ptrtoint (ptr @_Z2fpv to i64), i64 ptrtoint (ptr @__typeid__ZTSFvvE_global_addr to i64))
+}
+
+declare void @llvm.ubsantrap(i8 immarg)
+
+declare hidden void @_Z2fpv()
+
+!0 = !{i64 0, !"_ZTSFvvE"}
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