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[SROA] Improve handleling of assumes bundles by SROA

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This patch fixes this crash https://gcc.godbolt.org/z/Ps8d1e
And gives SROA the ability to remove assumes if it allows promoting an alloca to register
Without removing assumes when it can't promote to register.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D86570
This commit is contained in:
Tyker 2020-08-28 21:46:16 +02:00
parent 2d55005b0d
commit 70c01602af
5 changed files with 56 additions and 10 deletions
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2
include/llvm/IR/Value.h
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@ -484,7 +484,7 @@ public:
void dropDroppableUsesIn(User &Usr);
/// Remove the droppable use \p U.
void dropDroppableUse(Use &U);
static void dropDroppableUse(Use &U);
/// Check if this value is used in the specified basic block.
bool isUsedInBasicBlock(const BasicBlock *BB) const;

2
lib/IR/Value.cpp
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@ -205,7 +205,7 @@ void Value::dropDroppableUse(Use &U) {
else {
U.set(UndefValue::get(U.get()->getType()));
CallInst::BundleOpInfo &BOI = Assume->getBundleOpInfoForOperand(OpNo);
BOI.Tag = getContext().pImpl->getOrInsertBundleTag("ignore");
BOI.Tag = Assume->getContext().pImpl->getOrInsertBundleTag("ignore");
}
return;
}

19
lib/Transforms/Scalar/SROA.cpp
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@ -268,6 +268,11 @@ public:
/// Access the dead users for this alloca.
ArrayRef<Instruction *> getDeadUsers() const { return DeadUsers; }
/// Access Uses that should be dropped if the alloca is promotable.
ArrayRef<Use *> getDeadUsesIfPromotable() const {
return DeadUseIfPromotable;
}
/// Access the dead operands referring to this alloca.
///
/// These are operands which have cannot actually be used to refer to the
@ -322,6 +327,9 @@ private:
/// they come from outside of the allocated space.
SmallVector<Instruction *, 8> DeadUsers;
/// Uses which will become dead if can promote the alloca.
SmallVector<Use *, 8> DeadUseIfPromotable;
/// Operands which will become dead if we rewrite the alloca.
///
/// These are operands that in their particular use can be replaced with
@ -926,8 +934,10 @@ private:
// FIXME: What about debug intrinsics? This matches old behavior, but
// doesn't make sense.
void visitIntrinsicInst(IntrinsicInst &II) {
if (II.isDroppable())
if (II.isDroppable()) {
AS.DeadUseIfPromotable.push_back(U);
return;
}
if (!IsOffsetKnown)
return PI.setAborted(&II);
@ -4350,6 +4360,13 @@ AllocaInst *SROA::rewritePartition(AllocaInst &AI, AllocaSlices &AS,
}
if (Promotable) {
for (Use *U : AS.getDeadUsesIfPromotable()) {
auto *OldInst = dyn_cast<Instruction>(U->get());
Value::dropDroppableUse(*U);
if (OldInst)
if (isInstructionTriviallyDead(OldInst))
DeadInsts.insert(OldInst);
}
if (PHIUsers.empty() && SelectUsers.empty()) {
// Promote the alloca.
PromotableAllocas.push_back(NewAI);

32
test/Transforms/SROA/assume.ll Normal file
View File

@ -0,0 +1,32 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -sroa -S | FileCheck %s
source_filename = "tmp.cpp"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%struct.n.2 = type { i8 }
%struct.bi = type { %class.as }
%class.as = type { %class.ao }
%class.ao = type { %class.ai }
%class.ai = type { i32, i32 }
define linkonce_odr dso_local void @_ZN2bg2baIiEC2ES_() unnamed_addr align 2 {
; CHECK-LABEL: @_ZN2bg2baIiEC2ES_(
; CHECK-NEXT: entry:
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "ignore"(%struct.bi* undef) ]
; CHECK-NEXT: ret void
;
entry:
%y = alloca i64, align 8
store i64 undef, i64* %y, align 8
%0 = bitcast i64* %y to %struct.n.2*
%1 = bitcast %struct.n.2* %0 to %struct.bi*
call void @llvm.assume(i1 true) [ "nonnull"(%struct.bi* %1) ]
ret void
}
; Function Attrs: nofree norecurse nounwind willreturn
declare void @llvm.assume(i1) #0
attributes #0 = { nofree norecurse nounwind willreturn }

11
test/Transforms/SROA/ignore-droppable.ll
View File

@ -38,9 +38,8 @@ define void @negative_assume_condition_use() {
define void @positive_multiple_assume_uses() {
; CHECK-LABEL: @positive_multiple_assume_uses(
; CHECK-NEXT: [[A:%.*]] = alloca { i8, i16 }, align 8
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"({ i8, i16 }* [[A]], i64 8), "align"({ i8, i16 }* [[A]], i64 16) ]
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "nonnull"({ i8, i16 }* [[A]]), "align"({ i8, i16 }* [[A]], i64 2) ]
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "ignore"({ i8, i16 }* undef, i64 8), "ignore"({ i8, i16 }* undef, i64 16) ]
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "ignore"({ i8, i16 }* undef), "ignore"({ i8, i16 }* undef, i64 2) ]
; CHECK-NEXT: ret void
;
%A = alloca {i8, i16}
@ -52,10 +51,8 @@ define void @positive_multiple_assume_uses() {
define void @positive_gep_assume_uses() {
; CHECK-LABEL: @positive_gep_assume_uses(
; CHECK-NEXT: [[A:%.*]] = alloca { i8, i16 }, align 8
; CHECK-NEXT: [[B:%.*]] = getelementptr { i8, i16 }, { i8, i16 }* [[A]], i32 0, i32 0
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "align"(i8* [[B]], i64 8), "align"(i8* [[B]], i64 16) ]
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "nonnull"(i8* [[B]]), "align"(i8* [[B]], i64 2) ]
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "ignore"(i8* undef, i64 8), "ignore"(i8* undef, i64 16) ]
; CHECK-NEXT: call void @llvm.assume(i1 true) [ "ignore"(i8* undef), "ignore"(i8* undef, i64 2) ]
; CHECK-NEXT: ret void
;
%A = alloca {i8, i16}