[llvm] [SandboxIR] Preserve the order of switch cases after revert. (PR #115577)
Jorge Gorbe Moya via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 12 12:21:35 PST 2024
https://github.com/slackito updated https://github.com/llvm/llvm-project/pull/115577
>From b266ea739a7678804c14c4752dbfd8f7d1beeebe Mon Sep 17 00:00:00 2001
From: Jorge Gorbe Moya <jgorbe at google.com>
Date: Fri, 8 Nov 2024 18:58:59 -0800
Subject: [PATCH 1/4] [SandboxIR] Preserve the order of switch cases after
revert.
Preserving the case order is not strictly necessary to preserve
semantics (for example, operations like SwitchInst::removeCase will
happily swap cases around). However, I'm planning to introduce an
optional verification step for SandboxIR that will use StructuralHash to
compare IR after a revert to the original IR to help catch tracker bugs,
and the order difference triggers a difference there.
---
llvm/include/llvm/SandboxIR/Tracker.h | 6 ++++--
llvm/lib/SandboxIR/Instruction.cpp | 2 +-
llvm/lib/SandboxIR/Tracker.cpp | 14 +++++++++++++-
llvm/unittests/SandboxIR/TrackerTest.cpp | 13 +++++++++++++
4 files changed, 31 insertions(+), 4 deletions(-)
diff --git a/llvm/include/llvm/SandboxIR/Tracker.h b/llvm/include/llvm/SandboxIR/Tracker.h
index 3e3e539a8c7c16..7db0fc23c75fb9 100644
--- a/llvm/include/llvm/SandboxIR/Tracker.h
+++ b/llvm/include/llvm/SandboxIR/Tracker.h
@@ -315,12 +315,14 @@ class SwitchAddCase : public IRChangeBase {
class SwitchRemoveCase : public IRChangeBase {
SwitchInst *Switch;
+ unsigned Index;
ConstantInt *Val;
BasicBlock *Dest;
public:
- SwitchRemoveCase(SwitchInst *Switch, ConstantInt *Val, BasicBlock *Dest)
- : Switch(Switch), Val(Val), Dest(Dest) {}
+ SwitchRemoveCase(SwitchInst *Switch, unsigned Index, ConstantInt *Val,
+ BasicBlock *Dest)
+ : Switch(Switch), Index(Index), Val(Val), Dest(Dest) {}
void revert(Tracker &Tracker) final;
void accept() final {}
#ifndef NDEBUG
diff --git a/llvm/lib/SandboxIR/Instruction.cpp b/llvm/lib/SandboxIR/Instruction.cpp
index df941b2fa81efe..2df51a5947c173 100644
--- a/llvm/lib/SandboxIR/Instruction.cpp
+++ b/llvm/lib/SandboxIR/Instruction.cpp
@@ -1133,7 +1133,7 @@ void SwitchInst::addCase(ConstantInt *OnVal, BasicBlock *Dest) {
SwitchInst::CaseIt SwitchInst::removeCase(CaseIt It) {
auto &Case = *It;
Ctx.getTracker().emplaceIfTracking<SwitchRemoveCase>(
- this, Case.getCaseValue(), Case.getCaseSuccessor());
+ this, Case.getCaseIndex(), Case.getCaseValue(), Case.getCaseSuccessor());
auto *LLVMSwitch = cast<llvm::SwitchInst>(Val);
unsigned CaseNum = It - case_begin();
diff --git a/llvm/lib/SandboxIR/Tracker.cpp b/llvm/lib/SandboxIR/Tracker.cpp
index abcad39330094d..a6f25670c55207 100644
--- a/llvm/lib/SandboxIR/Tracker.cpp
+++ b/llvm/lib/SandboxIR/Tracker.cpp
@@ -170,7 +170,19 @@ void CatchSwitchAddHandler::revert(Tracker &Tracker) {
LLVMCSI->removeHandler(LLVMCSI->handler_begin() + HandlerIdx);
}
-void SwitchRemoveCase::revert(Tracker &Tracker) { Switch->addCase(Val, Dest); }
+void SwitchRemoveCase::revert(Tracker &Tracker) {
+ // removeCase swaps the last case with the deleted one. To revert it, we use
+ // addCase (which adds the new case to the end), and swap the newly-added
+ // value and successor operands to the positions for the original case index.
+ Switch->addCase(Val, Dest);
+ auto ValUseA = Switch->getOperandUse(2 + Index * 2);
+ auto SucUseA = Switch->getOperandUse(2 + Index * 2 + 1);
+ unsigned NumOps = Switch->getNumOperands();
+ auto ValUseB = Switch->getOperandUse(NumOps - 2);
+ auto SucUseB = Switch->getOperandUse(NumOps - 2 + 1);
+ ValUseA.swap(ValUseB);
+ SucUseA.swap(SucUseB);
+}
#ifndef NDEBUG
void SwitchRemoveCase::dump() const {
diff --git a/llvm/unittests/SandboxIR/TrackerTest.cpp b/llvm/unittests/SandboxIR/TrackerTest.cpp
index 6d060854949e1f..71c4c3d0ea9210 100644
--- a/llvm/unittests/SandboxIR/TrackerTest.cpp
+++ b/llvm/unittests/SandboxIR/TrackerTest.cpp
@@ -963,6 +963,19 @@ define void @foo(i32 %cond0, i32 %cond1) {
EXPECT_EQ(Switch->getNumCases(), 2u);
EXPECT_EQ(Switch->findCaseDest(BB0), Zero);
EXPECT_EQ(Switch->findCaseDest(BB1), One);
+
+ // Check order is preserved after reverting multiple removeCase invocations.
+ Ctx.save();
+ Switch->removeCase(Switch->findCaseValue(Zero));
+ Switch->removeCase(Switch->findCaseValue(One));
+ EXPECT_EQ(Switch->getNumCases(), 0u);
+ Ctx.revert();
+ EXPECT_EQ(Switch->getNumCases(), 2u);
+ EXPECT_EQ(Switch->findCaseDest(BB0), Zero);
+ EXPECT_EQ(Switch->findCaseDest(BB1), One);
+ EXPECT_EQ(Switch->getSuccessor(0), OrigDefaultDest);
+ EXPECT_EQ(Switch->getSuccessor(1), BB0);
+ EXPECT_EQ(Switch->getSuccessor(2), BB1);
}
TEST_F(TrackerTest, SelectInst) {
>From 6bccc01ac4e34dabd081d1c4dcfbc50ae616856f Mon Sep 17 00:00:00 2001
From: Jorge Gorbe Moya <jgorbe at google.com>
Date: Mon, 11 Nov 2024 14:06:47 -0800
Subject: [PATCH 2/4] Added a separate "switch preserves successor order" test.
The new test also tests a couple more situations, as requested during
review.
---
llvm/unittests/SandboxIR/TrackerTest.cpp | 76 +++++++++++++++++++++++-
1 file changed, 73 insertions(+), 3 deletions(-)
diff --git a/llvm/unittests/SandboxIR/TrackerTest.cpp b/llvm/unittests/SandboxIR/TrackerTest.cpp
index 71c4c3d0ea9210..077219b52260d7 100644
--- a/llvm/unittests/SandboxIR/TrackerTest.cpp
+++ b/llvm/unittests/SandboxIR/TrackerTest.cpp
@@ -964,18 +964,88 @@ define void @foo(i32 %cond0, i32 %cond1) {
EXPECT_EQ(Switch->findCaseDest(BB0), Zero);
EXPECT_EQ(Switch->findCaseDest(BB1), One);
- // Check order is preserved after reverting multiple removeCase invocations.
+}
+
+TEST_F(TrackerTest, SwitchInstPreservesSuccesorOrder) {
+ parseIR(C, R"IR(
+define void @foo(i32 %cond0) {
+ entry:
+ switch i32 %cond0, label %default [ i32 0, label %bb0
+ i32 1, label %bb1
+ i32 2, label %bb2 ]
+ bb0:
+ ret void
+ bb1:
+ ret void
+ bb2:
+ ret void
+ default:
+ ret void
+}
+)IR");
+ Function &LLVMF = *M->getFunction("foo");
+ auto *LLVMEntry = getBasicBlockByName(LLVMF, "entry");
+
+ sandboxir::Context Ctx(C);
+ [[maybe_unused]] auto &F = *Ctx.createFunction(&LLVMF);
+ auto *Entry = cast<sandboxir::BasicBlock>(Ctx.getValue(LLVMEntry));
+ auto *BB0 = cast<sandboxir::BasicBlock>(
+ Ctx.getValue(getBasicBlockByName(LLVMF, "bb0")));
+ auto *BB1 = cast<sandboxir::BasicBlock>(
+ Ctx.getValue(getBasicBlockByName(LLVMF, "bb1")));
+ auto *BB2 = cast<sandboxir::BasicBlock>(
+ Ctx.getValue(getBasicBlockByName(LLVMF, "bb2")));
+ auto *Switch = cast<sandboxir::SwitchInst>(&*Entry->begin());
+
+ auto *DefaultDest = Switch->getDefaultDest();
+ auto *Zero = sandboxir::ConstantInt::get(sandboxir::Type::getInt32Ty(Ctx), 0);
+ auto *One = sandboxir::ConstantInt::get(sandboxir::Type::getInt32Ty(Ctx), 1);
+ auto *Two = sandboxir::ConstantInt::get(sandboxir::Type::getInt32Ty(Ctx), 2);
+
+ // Check that we can properly revert a removeCase multiple positions apart
+ // from the end of the operand list.
Ctx.save();
Switch->removeCase(Switch->findCaseValue(Zero));
+ EXPECT_EQ(Switch->getNumCases(), 2u);
+ Ctx.revert();
+ EXPECT_EQ(Switch->getNumCases(), 3u);
+ EXPECT_EQ(Switch->findCaseDest(BB0), Zero);
+ EXPECT_EQ(Switch->findCaseDest(BB1), One);
+ EXPECT_EQ(Switch->findCaseDest(BB2), Two);
+ EXPECT_EQ(Switch->getSuccessor(0), DefaultDest);
+ EXPECT_EQ(Switch->getSuccessor(1), BB0);
+ EXPECT_EQ(Switch->getSuccessor(2), BB1);
+ EXPECT_EQ(Switch->getSuccessor(3), BB2);
+
+ // Check that we can properly revert a removeCase of the last case.
+ Ctx.save();
+ Switch->removeCase(Switch->findCaseValue(Two));
+ EXPECT_EQ(Switch->getNumCases(), 2u);
+ Ctx.revert();
+ EXPECT_EQ(Switch->getNumCases(), 3u);
+ EXPECT_EQ(Switch->findCaseDest(BB0), Zero);
+ EXPECT_EQ(Switch->findCaseDest(BB1), One);
+ EXPECT_EQ(Switch->findCaseDest(BB2), Two);
+ EXPECT_EQ(Switch->getSuccessor(0), DefaultDest);
+ EXPECT_EQ(Switch->getSuccessor(1), BB0);
+ EXPECT_EQ(Switch->getSuccessor(2), BB1);
+ EXPECT_EQ(Switch->getSuccessor(3), BB2);
+
+ // Check order is preserved after reverting multiple removeCase invocations.
+ Ctx.save();
Switch->removeCase(Switch->findCaseValue(One));
+ Switch->removeCase(Switch->findCaseValue(Zero));
+ Switch->removeCase(Switch->findCaseValue(Two));
EXPECT_EQ(Switch->getNumCases(), 0u);
Ctx.revert();
- EXPECT_EQ(Switch->getNumCases(), 2u);
+ EXPECT_EQ(Switch->getNumCases(), 3u);
EXPECT_EQ(Switch->findCaseDest(BB0), Zero);
EXPECT_EQ(Switch->findCaseDest(BB1), One);
- EXPECT_EQ(Switch->getSuccessor(0), OrigDefaultDest);
+ EXPECT_EQ(Switch->findCaseDest(BB2), Two);
+ EXPECT_EQ(Switch->getSuccessor(0), DefaultDest);
EXPECT_EQ(Switch->getSuccessor(1), BB0);
EXPECT_EQ(Switch->getSuccessor(2), BB1);
+ EXPECT_EQ(Switch->getSuccessor(3), BB2);
}
TEST_F(TrackerTest, SelectInst) {
>From 120eb87812b3de37a49ae8f14a90dd8a8181a094 Mon Sep 17 00:00:00 2001
From: Jorge Gorbe Moya <jgorbe at google.com>
Date: Mon, 11 Nov 2024 14:17:30 -0800
Subject: [PATCH 3/4] clang-format
---
llvm/unittests/SandboxIR/TrackerTest.cpp | 1 -
1 file changed, 1 deletion(-)
diff --git a/llvm/unittests/SandboxIR/TrackerTest.cpp b/llvm/unittests/SandboxIR/TrackerTest.cpp
index 077219b52260d7..4f2cfa6b06ecd2 100644
--- a/llvm/unittests/SandboxIR/TrackerTest.cpp
+++ b/llvm/unittests/SandboxIR/TrackerTest.cpp
@@ -963,7 +963,6 @@ define void @foo(i32 %cond0, i32 %cond1) {
EXPECT_EQ(Switch->getNumCases(), 2u);
EXPECT_EQ(Switch->findCaseDest(BB0), Zero);
EXPECT_EQ(Switch->findCaseDest(BB1), One);
-
}
TEST_F(TrackerTest, SwitchInstPreservesSuccesorOrder) {
>From 17ea6d8da8b5a6474d52fc7165c11817e31fa4d8 Mon Sep 17 00:00:00 2001
From: Jorge Gorbe Moya <jgorbe at google.com>
Date: Tue, 12 Nov 2024 12:20:56 -0800
Subject: [PATCH 4/4] Avoid depending on llvm::SwitchInst::removeCase impl
details.
---
llvm/include/llvm/SandboxIR/Tracker.h | 13 ++++++------
llvm/lib/SandboxIR/Instruction.cpp | 4 +---
llvm/lib/SandboxIR/Tracker.cpp | 29 +++++++++++++++++----------
3 files changed, 26 insertions(+), 20 deletions(-)
diff --git a/llvm/include/llvm/SandboxIR/Tracker.h b/llvm/include/llvm/SandboxIR/Tracker.h
index 7db0fc23c75fb9..dab20eb809ba08 100644
--- a/llvm/include/llvm/SandboxIR/Tracker.h
+++ b/llvm/include/llvm/SandboxIR/Tracker.h
@@ -315,14 +315,15 @@ class SwitchAddCase : public IRChangeBase {
class SwitchRemoveCase : public IRChangeBase {
SwitchInst *Switch;
- unsigned Index;
- ConstantInt *Val;
- BasicBlock *Dest;
+ struct Case {
+ ConstantInt *Val;
+ BasicBlock *Dest;
+ };
+ SmallVector<Case> Cases;
public:
- SwitchRemoveCase(SwitchInst *Switch, unsigned Index, ConstantInt *Val,
- BasicBlock *Dest)
- : Switch(Switch), Index(Index), Val(Val), Dest(Dest) {}
+ SwitchRemoveCase(SwitchInst *Switch);
+
void revert(Tracker &Tracker) final;
void accept() final {}
#ifndef NDEBUG
diff --git a/llvm/lib/SandboxIR/Instruction.cpp b/llvm/lib/SandboxIR/Instruction.cpp
index 2df51a5947c173..0a7cd95124bb51 100644
--- a/llvm/lib/SandboxIR/Instruction.cpp
+++ b/llvm/lib/SandboxIR/Instruction.cpp
@@ -1131,9 +1131,7 @@ void SwitchInst::addCase(ConstantInt *OnVal, BasicBlock *Dest) {
}
SwitchInst::CaseIt SwitchInst::removeCase(CaseIt It) {
- auto &Case = *It;
- Ctx.getTracker().emplaceIfTracking<SwitchRemoveCase>(
- this, Case.getCaseIndex(), Case.getCaseValue(), Case.getCaseSuccessor());
+ Ctx.getTracker().emplaceIfTracking<SwitchRemoveCase>(this);
auto *LLVMSwitch = cast<llvm::SwitchInst>(Val);
unsigned CaseNum = It - case_begin();
diff --git a/llvm/lib/SandboxIR/Tracker.cpp b/llvm/lib/SandboxIR/Tracker.cpp
index a6f25670c55207..bf3d525ab83cd4 100644
--- a/llvm/lib/SandboxIR/Tracker.cpp
+++ b/llvm/lib/SandboxIR/Tracker.cpp
@@ -170,18 +170,25 @@ void CatchSwitchAddHandler::revert(Tracker &Tracker) {
LLVMCSI->removeHandler(LLVMCSI->handler_begin() + HandlerIdx);
}
+SwitchRemoveCase::SwitchRemoveCase(SwitchInst *Switch): Switch(Switch) {
+ for (const auto& C : Switch->cases()) {
+ Cases.push_back({C.getCaseValue(), C.getCaseSuccessor()});
+ }
+}
+
void SwitchRemoveCase::revert(Tracker &Tracker) {
- // removeCase swaps the last case with the deleted one. To revert it, we use
- // addCase (which adds the new case to the end), and swap the newly-added
- // value and successor operands to the positions for the original case index.
- Switch->addCase(Val, Dest);
- auto ValUseA = Switch->getOperandUse(2 + Index * 2);
- auto SucUseA = Switch->getOperandUse(2 + Index * 2 + 1);
- unsigned NumOps = Switch->getNumOperands();
- auto ValUseB = Switch->getOperandUse(NumOps - 2);
- auto SucUseB = Switch->getOperandUse(NumOps - 2 + 1);
- ValUseA.swap(ValUseB);
- SucUseA.swap(SucUseB);
+ // llvm::SwitchInst doesn't give us any API to insert cases at a specific
+ // index. In order to preserve the original ordering, we save all of them and,
+ // when reverting, clear them all then insert them in the desired order. This
+ // still relies on the fact that `addCase` will insert them at the end, but it
+ // is documented to invalidate `case_end()` so it's probably okay.
+ unsigned NumCases = Switch->getNumCases();
+ for (unsigned I = 0; I < NumCases; ++I) {
+ Switch->removeCase(Switch->case_begin());
+ }
+ for (auto &Case : Cases) {
+ Switch->addCase(Case.Val, Case.Dest);
+ }
}
#ifndef NDEBUG
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