[llvm] [InstCombine] If inst in unreachable refers to an inst change it to poison (#65107) (PR #78444)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 6 00:41:32 PST 2024
https://github.com/nikic updated https://github.com/llvm/llvm-project/pull/78444
>From fef88f37b547a72ca20712626213fa562d1e8adc Mon Sep 17 00:00:00 2001
From: Hanbum Park <kese111 at gmail.com>
Date: Sat, 20 Jan 2024 04:22:57 +0900
Subject: [PATCH 1/2] [InstCombine] If Inst in unreachable refers to Inst
change it to poison (#65107)
Instructions in unreachable basic blocks are removed, but terminators
are not. In this case, even instructions that are only referenced by
a terminator, such as a return instruction, cannot be processed
properly.
This patch changes the operand of terminator instruction in an
unreachable basic block to poison if it refers to the instruction,
allowing the instruction to be properly processed.
---
llvm/include/llvm/Transforms/Utils/Local.h | 7 +
.../InstCombine/InstructionCombining.cpp | 9 +-
llvm/lib/Transforms/Utils/Local.cpp | 22 ++-
.../InstCombine/phi-select-constant.ll | 3 +-
llvm/test/Transforms/InstCombine/pr63791.ll | 2 +-
.../InstCombine/sink_to_unreachable.ll | 154 ++++++++++++++++++
.../InstCombine/unreachable-code.ll | 57 +++++++
7 files changed, 246 insertions(+), 8 deletions(-)
diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index 2df3c9049c7d62..e8bda9a7895ceb 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -357,6 +357,13 @@ Value *salvageDebugInfoImpl(Instruction &I, uint64_t CurrentLocOps,
bool replaceAllDbgUsesWith(Instruction &From, Value &To, Instruction &DomPoint,
DominatorTree &DT);
+/// If a terminator in an unreachable basic block has an operand of type
+/// Instruction, transform it into poison. Return true if any operands
+/// are changed to poison. Original Values prior to being changed to poison
+/// are returned to PoisonedValues.
+bool handleUnreachableTerminator(Instruction *I,
+ SmallVectorImpl<Value *> &PoisonedValues);
+
/// Remove all instructions from a basic block other than its terminator
/// and any present EH pad instructions. Returns a pair where the first element
/// is the number of instructions (excluding debug info intrinsics) that have
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index b1e2262fac4794..78b69da63690d5 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3231,9 +3231,12 @@ void InstCombinerImpl::handleUnreachableFrom(
MadeIRChange = true;
}
- // RemoveDIs: to match behaviour in dbg.value mode, drop debug-info on
- // terminator too.
- BB->getTerminator()->dropDbgValues();
+ SmallVector<Value *> Changed;
+ if (handleUnreachableTerminator(BB->getTerminator(), Changed)) {
+ MadeIRChange = true;
+ for (Value *V : Changed)
+ addToWorklist(cast<Instruction>(V));
+ }
// Handle potentially dead successors.
for (BasicBlock *Succ : successors(BB))
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index e4aa25f7ac6ad3..2fd9f44e53f0bb 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -2762,6 +2762,23 @@ bool llvm::replaceAllDbgUsesWith(Instruction &From, Value &To,
return false;
}
+bool llvm::handleUnreachableTerminator(
+ Instruction *I, SmallVectorImpl<Value *> &PoisonedValues) {
+ bool Changed = false;
+ // RemoveDIs: erase debug-info on this instruction manually.
+ I->dropDbgValues();
+ for (Use &U : I->operands()) {
+ Value *Op = U.get();
+ if (isa<Instruction>(Op) && !Op->getType()->isTokenTy()) {
+ U.set(PoisonValue::get(Op->getType()));
+ PoisonedValues.push_back(Op);
+ Changed = true;
+ }
+ }
+
+ return Changed;
+}
+
std::pair<unsigned, unsigned>
llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) {
unsigned NumDeadInst = 0;
@@ -2769,8 +2786,9 @@ llvm::removeAllNonTerminatorAndEHPadInstructions(BasicBlock *BB) {
// Delete the instructions backwards, as it has a reduced likelihood of
// having to update as many def-use and use-def chains.
Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
- // RemoveDIs: erasing debug-info must be done manually.
- EndInst->dropDbgValues();
+ SmallVector<Value *> Uses;
+ handleUnreachableTerminator(EndInst, Uses);
+
while (EndInst != &BB->front()) {
// Delete the next to last instruction.
Instruction *Inst = &*--EndInst->getIterator();
diff --git a/llvm/test/Transforms/InstCombine/phi-select-constant.ll b/llvm/test/Transforms/InstCombine/phi-select-constant.ll
index 1260ef47f65ef4..601a3d208a0841 100644
--- a/llvm/test/Transforms/InstCombine/phi-select-constant.ll
+++ b/llvm/test/Transforms/InstCombine/phi-select-constant.ll
@@ -140,12 +140,11 @@ end:
define i16 @sink_to_unreachable_crash(i1 %a) {
; CHECK-LABEL: @sink_to_unreachable_crash(
; CHECK-NEXT: entry:
-; CHECK-NEXT: [[S:%.*]] = select i1 [[A:%.*]], i16 0, i16 5
; CHECK-NEXT: br label [[INF_LOOP:%.*]]
; CHECK: inf_loop:
; CHECK-NEXT: br label [[INF_LOOP]]
; CHECK: unreachable:
-; CHECK-NEXT: ret i16 [[S]]
+; CHECK-NEXT: ret i16 poison
;
entry:
%s = select i1 %a, i16 0, i16 5
diff --git a/llvm/test/Transforms/InstCombine/pr63791.ll b/llvm/test/Transforms/InstCombine/pr63791.ll
index a489b2e3e6221a..78cc1130fb33f0 100644
--- a/llvm/test/Transforms/InstCombine/pr63791.ll
+++ b/llvm/test/Transforms/InstCombine/pr63791.ll
@@ -17,7 +17,7 @@ define void @y() {
; CHECK: for.cond5.preheader.i:
; CHECK-NEXT: br i1 false, label [[FOR_INC19_I:%.*]], label [[FOR_COND1_LOOPEXIT_I:%.*]]
; CHECK: for.inc19.i:
-; CHECK-NEXT: br i1 false, label [[FOR_INC19_I]], label [[FOR_COND1_LOOPEXIT_I]]
+; CHECK-NEXT: br i1 poison, label [[FOR_INC19_I]], label [[FOR_COND1_LOOPEXIT_I]]
;
entry:
br label %for.cond.i
diff --git a/llvm/test/Transforms/InstCombine/sink_to_unreachable.ll b/llvm/test/Transforms/InstCombine/sink_to_unreachable.ll
index e788b634da8868..02ed22217854ea 100644
--- a/llvm/test/Transforms/InstCombine/sink_to_unreachable.ll
+++ b/llvm/test/Transforms/InstCombine/sink_to_unreachable.ll
@@ -157,3 +157,157 @@ bb3:
%p = phi i32 [0, %bb1], [%a, %bb2]
ret i32 %p
}
+
+define i1 @sink_to_unreachable_ret(i16 %X) {
+; CHECK-LABEL: @sink_to_unreachable_ret(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: br i1 true, label [[LOOP]], label [[UNREACH:%.*]]
+; CHECK: unreach:
+; CHECK-NEXT: ret i1 poison
+;
+entry:
+ br label %loop
+
+loop:
+ %p = icmp sgt i16 %X, 16
+ br i1 true, label %loop, label %unreach
+
+unreach:
+ ret i1 %p
+}
+
+define void @sink_to_unreachable_condbr(i16 %X) {
+; CHECK-LABEL: @sink_to_unreachable_condbr(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: br i1 true, label [[LOOP]], label [[UNREACH:%.*]]
+; CHECK: unreach:
+; CHECK-NEXT: br i1 poison, label [[DUMMY:%.*]], label [[LOOP]]
+; CHECK: dummy:
+; CHECK-NEXT: unreachable
+;
+entry:
+ br label %loop
+
+loop:
+ %p = icmp sgt i16 %X, 16
+ br i1 true, label %loop, label %unreach
+
+unreach:
+ br i1 %p, label %dummy, label %loop
+
+dummy:
+ unreachable
+}
+
+define void @sink_to_unreachable_switch(i16 %X) {
+; CHECK-LABEL: @sink_to_unreachable_switch(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: br i1 true, label [[LOOP]], label [[UNREACH:%.*]]
+; CHECK: unreach:
+; CHECK-NEXT: switch i16 poison, label [[UNREACH_RET:%.*]] [
+; CHECK-NEXT: ]
+; CHECK: unreach.ret:
+; CHECK-NEXT: unreachable
+;
+entry:
+ br label %loop
+
+loop:
+ %quantum = srem i16 %X, 32
+ br i1 true, label %loop, label %unreach
+
+unreach:
+ switch i16 %quantum, label %unreach.ret []
+
+unreach.ret:
+ unreachable
+}
+
+define void @sink_to_unreachable_indirectbr(ptr %Ptr) {
+; CHECK-LABEL: @sink_to_unreachable_indirectbr(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: br i1 true, label [[LOOP]], label [[UNREACH:%.*]]
+; CHECK: unreach:
+; CHECK-NEXT: indirectbr ptr poison, [label %loop]
+;
+entry:
+ br label %loop
+
+loop:
+ %gep = getelementptr inbounds ptr, ptr %Ptr, i16 1
+ br i1 true, label %loop, label %unreach
+
+unreach:
+ indirectbr ptr %gep, [label %loop]
+}
+
+define void @sink_to_unreachable_invoke(ptr %Ptr) personality ptr @__CxxFrameHandler3 {
+; CHECK-LABEL: @sink_to_unreachable_invoke(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[LOOP:%.*]]
+; CHECK: loop:
+; CHECK-NEXT: br i1 true, label [[LOOP]], label [[UNREACH:%.*]]
+; CHECK: unreach:
+; CHECK-NEXT: invoke void poison(i1 false)
+; CHECK-NEXT: to label [[DUMMY:%.*]] unwind label [[ICATCH_DISPATCH:%.*]]
+; CHECK: unreach2:
+; CHECK-NEXT: invoke void @__CxxFrameHandler3(ptr poison)
+; CHECK-NEXT: to label [[DUMMY]] unwind label [[ICATCH_DISPATCH]]
+; CHECK: unreach3:
+; CHECK-NEXT: [[CLEAN:%.*]] = cleanuppad within none []
+; CHECK-NEXT: invoke void @__CxxFrameHandler3(ptr poison) [ "funclet"(token [[CLEAN]]) ]
+; CHECK-NEXT: to label [[DUMMY]] unwind label [[ICATCH_DISPATCH]]
+; CHECK: icatch.dispatch:
+; CHECK-NEXT: [[TMP1:%.*]] = catchswitch within none [label %icatch] unwind to caller
+; CHECK: icatch:
+; CHECK-NEXT: [[TMP2:%.*]] = catchpad within [[TMP1]] [ptr null, i32 64, ptr null]
+; CHECK-NEXT: catchret from [[TMP2]] to label [[DUMMY2:%.*]]
+; CHECK: dummy:
+; CHECK-NEXT: ret void
+; CHECK: dummy2:
+; CHECK-NEXT: ret void
+;
+entry:
+ br label %loop
+
+loop:
+ %gep = getelementptr inbounds ptr, ptr %Ptr, i16 1
+ br i1 true, label %loop, label %unreach
+
+unreach:
+ invoke void %gep(i1 false)
+ to label %dummy unwind label %icatch.dispatch
+
+unreach2:
+ invoke void @__CxxFrameHandler3(ptr %gep)
+ to label %dummy unwind label %icatch.dispatch
+
+unreach3:
+ %clean = cleanuppad within none []
+ invoke void @__CxxFrameHandler3(ptr %gep) [ "funclet"(token %clean) ]
+ to label %dummy unwind label %icatch.dispatch
+
+icatch.dispatch:
+ %tmp1 = catchswitch within none [label %icatch] unwind to caller
+
+icatch:
+ %tmp2 = catchpad within %tmp1 [ptr null, i32 64, ptr null]
+ catchret from %tmp2 to label %dummy2
+
+dummy:
+ ret void
+
+dummy2:
+ ret void
+}
+
+declare void @may_throw()
+declare i32 @__CxxFrameHandler3(...)
diff --git a/llvm/test/Transforms/InstCombine/unreachable-code.ll b/llvm/test/Transforms/InstCombine/unreachable-code.ll
index 72ef1c79f3a8e5..bb4be9fa71f83c 100644
--- a/llvm/test/Transforms/InstCombine/unreachable-code.ll
+++ b/llvm/test/Transforms/InstCombine/unreachable-code.ll
@@ -540,6 +540,63 @@ bb2:
br label %bb
}
+declare void @invoke(ptr)
+declare i32 @__gxx_personality_v0(...)
+define void @test(i1 %x) personality ptr @__gxx_personality_v0 {
+; CHECK-LABEL: define void @test
+; CHECK-SAME: (i1 [[X:%.*]]) personality ptr @__gxx_personality_v0 {
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br i1 [[X]], label [[IF_ELSE:%.*]], label [[CLEAN1:%.*]]
+; CHECK: if.else:
+; CHECK-NEXT: store i32 1, ptr undef, align 4
+; CHECK-NEXT: invoke void @invoke(ptr poison)
+; CHECK-NEXT: to label [[CONT:%.*]] unwind label [[LPAD5:%.*]]
+; CHECK: cont:
+; CHECK-NEXT: invoke void @invoke(ptr poison)
+; CHECK-NEXT: to label [[CLEAN1]] unwind label [[LPAD6:%.*]]
+; CHECK: lpad5:
+; CHECK-NEXT: [[TMP0:%.*]] = landingpad { ptr, i32 }
+; CHECK-NEXT: cleanup
+; CHECK-NEXT: br label [[CLEAN1]]
+; CHECK: lpad6:
+; CHECK-NEXT: [[TMP1:%.*]] = landingpad { ptr, i32 }
+; CHECK-NEXT: cleanup
+; CHECK-NEXT: br label [[CLEAN2:%.*]]
+; CHECK: clean1:
+; CHECK-NEXT: ret void
+; CHECK: clean2:
+; CHECK-NEXT: ret void
+;
+entry:
+ %ref = alloca ptr
+ br i1 %x, label %if.else, label %clean1
+
+if.else:
+ store i32 1, ptr undef
+ invoke void @invoke(ptr %ref)
+ to label %cont unwind label %lpad5
+
+cont:
+ invoke void @invoke(ptr %ref)
+ to label %clean1 unwind label %lpad6
+
+lpad5:
+ %13 = landingpad { ptr, i32 }
+ cleanup
+ br label %clean1
+
+lpad6:
+ %14 = landingpad { ptr, i32 }
+ cleanup
+ br label %clean2
+
+clean1:
+ ret void
+
+clean2:
+ ret void
+}
+
;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
; DEFAULT_ITER: {{.*}}
; MAX1: {{.*}}
>From 5f59287a68b062d71e39c7429a933682361946fc Mon Sep 17 00:00:00 2001
From: Nikita Popov <github at npopov.com>
Date: Wed, 6 Mar 2024 09:41:26 +0100
Subject: [PATCH 2/2] Update llvm/include/llvm/Transforms/Utils/Local.h
Co-authored-by: Yingwei Zheng <dtcxzyw at qq.com>
---
llvm/include/llvm/Transforms/Utils/Local.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/include/llvm/Transforms/Utils/Local.h b/llvm/include/llvm/Transforms/Utils/Local.h
index e8bda9a7895ceb..001f61cecc3d2f 100644
--- a/llvm/include/llvm/Transforms/Utils/Local.h
+++ b/llvm/include/llvm/Transforms/Utils/Local.h
@@ -360,7 +360,7 @@ bool replaceAllDbgUsesWith(Instruction &From, Value &To, Instruction &DomPoint,
/// If a terminator in an unreachable basic block has an operand of type
/// Instruction, transform it into poison. Return true if any operands
/// are changed to poison. Original Values prior to being changed to poison
-/// are returned to PoisonedValues.
+/// are returned in \p PoisonedValues.
bool handleUnreachableTerminator(Instruction *I,
SmallVectorImpl<Value *> &PoisonedValues);
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