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[IPSCCP] Push constant struct params into callees #111805

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120 changes: 120 additions & 0 deletions llvm/lib/Transforms/IPO/SCCP.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
#include "llvm/IR/AttributeMask.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ModRef.h"
Expand Down Expand Up @@ -265,6 +266,125 @@ static bool runIPSCCP(
}
}

// If a function has one use, has an alloca parameter, and its caller has
// nothing but geps/stores to the alloca, push the alloca definition and all
// stores/geps into the caller. For now, rely on argpromotion to clean up the
// dead arguments left in the caller
for (auto &F : M) {
if (F.hasOneUse() && canTrackArgumentsInterprocedurally(&F)) {
CallInst *CI = dyn_cast<CallInst>(*F.user_begin());
if (!CI)
continue;
for (auto &Arg : CI->args()) {
auto AI = dyn_cast<AllocaInst>(Arg);
if (!AI)
continue;

auto GetAllocaUsers = [&CI](AllocaInst *AI,
SmallVector<Value *> &AllocaUsers) -> bool {
for (User *U : AI->users()) {
if (U == CI)
continue;

auto I = dyn_cast<Instruction>(U);
if (!I)
continue;
switch (I->getOpcode()) {
default: {
return false;
}
case Instruction::Store: {
auto SI = cast<StoreInst>(U);
if (SI->isVolatile() || !isa<Constant>(SI->getValueOperand())) {
return false;
}
AllocaUsers.push_back(SI);
break;
}
case Instruction::GetElementPtr: {
auto GEP = cast<GetElementPtrInst>(U);
auto SI = dyn_cast<StoreInst>(*GEP->users().begin());
if (GEP->getNumUses() != 1 || !SI ||
!isa<Constant>(SI->getValueOperand())) {
return false;
}
AllocaUsers.push_back(GEP);
break;
}
}
}
return !AllocaUsers.empty();
};

SmallVector<Value *> AllocaUsers;
if (!GetAllocaUsers(AI, AllocaUsers))
continue;

// Copy uses of the Alloca to the callee
IRBuilder<> B(&F.getEntryBlock().front());
DataLayout DL = AI->getDataLayout();
AllocaInst *NewAI =
B.CreateAlloca(AI->getAllocatedType(), nullptr, AI->getName());
F.getArg(Arg.getOperandNo())->replaceAllUsesWith(NewAI);
NewAI->setAlignment(AI->getAlign());

for (auto U : AllocaUsers) {
switch (cast<Instruction>(U)->getOpcode()) {
default:
llvm_unreachable("Illegal user type in AllocaUsers");
case Instruction::Store: {
auto SI = cast<StoreInst>(U);
auto NewStore = B.CreateStore(SI->getValueOperand(), NewAI);
NewStore->setAlignment(SI->getAlign());
break;
}
case Instruction::GetElementPtr: {
auto GEP = cast<GetElementPtrInst>(U);

SmallVector<Value *> GepIndices;
for (unsigned i = 0; i < GEP->getNumIndices(); i++)
GepIndices.push_back(GEP->getOperand(i + 1));

GetElementPtrInst *NewGep = cast<GetElementPtrInst>(
B.CreateGEP(GEP->getSourceElementType(), NewAI, GepIndices));
NewGep->setNoWrapFlags(GEP->getNoWrapFlags());

auto SI = cast<StoreInst>(*GEP->users().begin());
auto NewStore = B.CreateStore(SI->getValueOperand(), NewGep);
NewStore->setAlignment(SI->getAlign());
}
}
}

// Remove old uses of the Alloca in the caller
while (!AllocaUsers.empty()) {
Instruction *I = cast<Instruction>(AllocaUsers.pop_back_val());
switch (I->getOpcode()) {
default:
llvm_unreachable("Illegal user type when removing Alloca users");
case Instruction::Store: {
I->removeFromParent();
I->deleteValue();
break;
}
case Instruction::GetElementPtr: {
auto SI = cast<Instruction>(*I->users().begin());
SI->removeFromParent();
SI->deleteValue();
I->removeFromParent();
I->deleteValue();
}
}
}
MadeChanges = true;

// TODO:
// - delete dead params here instead of relying on argpromotion
// - remove empty alloca instruction
}
}
}

// If we inferred constant or undef return values for a function, we replaced
// all call uses with the inferred value. This means we don't need to bother
// actually returning anything from the function. Replace all return
Expand Down
6 changes: 2 additions & 4 deletions llvm/test/Transforms/PhaseOrdering/dce-after-argument-promotion.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -9,10 +9,8 @@

define internal void @f(ptr byval(%struct.ss) align 8 %b, ptr byval(i32) align 4 %X) noinline nounwind {
; CHECK-LABEL: define {{[^@]+}}@f
; CHECK-SAME: (i32 [[B_0:%.*]]){{[^#]*}} #[[ATTR0:[0-9]+]] {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TEMP:%.*]] = add i32 [[B_0]], 1
; CHECK-NEXT: store i32 [[TEMP]], ptr [[DUMMY]], align 4
; CHECK-NEXT: store i32 2, ptr [[DUMMY]], align 4
; CHECK-NEXT: ret void
;
entry:
Expand All @@ -27,7 +25,7 @@ define i32 @test(ptr %X) {
; CHECK-LABEL: define {{[^@]+}}@test
; CHECK-SAME: (ptr {{[^%]*}} [[X:%.*]]){{[^#]*}} #[[ATTR1:[0-9]+]] {
; CHECK-NEXT: entry:
; CHECK-NEXT: tail call {{.*}}void @f(i32 1)
; CHECK-NEXT: tail call {{.*}}void @f()
; CHECK-NEXT: ret i32 0
;
entry:
Expand Down
102 changes: 102 additions & 0 deletions llvm/test/Transforms/SCCP/push_stores.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,102 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -passes=ipsccp,argpromotion < %s | FileCheck %s

@sudoku0 = internal global [9 x [9 x i32]] zeroinitializer
@sudoku1 = internal global [9 x [9 x i32]] zeroinitializer

declare void @callee2(ptr nocapture nonnull readonly %0)

define internal i64 @callee(ptr nocapture readonly %0, ptr nocapture readonly %1) local_unnamed_addr {
; CHECK-LABEL: define internal i64 @callee() local_unnamed_addr {
; CHECK-NEXT: [[TMP1:%.*]] = alloca { ptr, i64 }, align 8
; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i8, ptr [[TMP1]], i64 8
; CHECK-NEXT: store i64 4, ptr [[TMP2]], align 8
; CHECK-NEXT: store ptr @sudoku1, ptr [[TMP1]], align 8
; CHECK-NEXT: [[TMP3:%.*]] = alloca { ptr, i64 }, align 8
; CHECK-NEXT: [[TMP4:%.*]] = getelementptr inbounds i8, ptr [[TMP3]], i64 8
; CHECK-NEXT: store i64 4, ptr [[TMP4]], align 8
; CHECK-NEXT: store ptr @sudoku0, ptr [[TMP3]], align 8
; CHECK-NEXT: [[MEGASTRUCT:%.*]] = alloca { ptr, ptr, { ptr, i64 }, { ptr, i64 } }, align 8
; CHECK-NEXT: [[ALLOCA0:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[ALLOCA1:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[TMP5:%.*]] = load ptr, ptr [[TMP3]], align 8
; CHECK-NEXT: [[GEP_0_1:%.*]] = getelementptr inbounds i8, ptr [[TMP3]], i64 8
; CHECK-NEXT: [[TMP6:%.*]] = load i64, ptr [[GEP_0_1]], align 8
; CHECK-NEXT: [[TMP7:%.*]] = load ptr, ptr [[TMP3]], align 8
; CHECK-NEXT: [[GEP_1_1:%.*]] = getelementptr inbounds i8, ptr [[TMP1]], i64 8
; CHECK-NEXT: [[TMP8:%.*]] = load i64, ptr [[GEP_1_1]], align 8
; CHECK-NEXT: store ptr [[ALLOCA0]], ptr [[MEGASTRUCT]], align 8
; CHECK-NEXT: [[MEGASTRUCT_GEP_1:%.*]] = getelementptr inbounds i8, ptr [[MEGASTRUCT]], i64 8
; CHECK-NEXT: store ptr [[ALLOCA1]], ptr [[MEGASTRUCT_GEP_1]], align 8
; CHECK-NEXT: [[MEGASTRUCT_GEP_2:%.*]] = getelementptr inbounds i8, ptr [[MEGASTRUCT]], i64 16
; CHECK-NEXT: store ptr [[TMP5]], ptr [[MEGASTRUCT_GEP_2]], align 8
; CHECK-NEXT: [[MEGASTRUCT_GEP_3:%.*]] = getelementptr inbounds i8, ptr [[MEGASTRUCT]], i64 24
; CHECK-NEXT: store i64 [[TMP6]], ptr [[MEGASTRUCT_GEP_3]], align 8
; CHECK-NEXT: [[MEGASTRUCT_GEP_4:%.*]] = getelementptr inbounds i8, ptr [[MEGASTRUCT]], i64 32
; CHECK-NEXT: store ptr [[TMP7]], ptr [[MEGASTRUCT_GEP_4]], align 8
; CHECK-NEXT: [[MEGASTRUCT_GEP_5:%.*]] = getelementptr inbounds i8, ptr [[MEGASTRUCT]], i64 40
; CHECK-NEXT: store i64 [[TMP8]], ptr [[MEGASTRUCT_GEP_5]], align 8
; CHECK-NEXT: call fastcc void @callee2(ptr [[MEGASTRUCT]])
; CHECK-NEXT: ret i64 poison
;
%megastruct = alloca { ptr, ptr, { ptr, i64 }, { ptr, i64 } }

%alloca0 = alloca i32, align 4
%alloca1 = alloca i32, align 4

%3 = load ptr, ptr %0, align 8
%gep.0.1 = getelementptr inbounds i8, ptr %0, i64 8
%4 = load i64, ptr %gep.0.1, align 8

%5 = load ptr, ptr %0, align 8
%gep.1.1 = getelementptr inbounds i8, ptr %1, i64 8
%6 = load i64, ptr %gep.1.1, align 8

store ptr %alloca0, ptr %megastruct, align 8
%megastruct.gep.1 = getelementptr inbounds i8, ptr %megastruct, i64 8
store ptr %alloca1, ptr %megastruct.gep.1, align 8

%megastruct.gep.2 = getelementptr inbounds i8, ptr %megastruct, i64 16
store ptr %3, ptr %megastruct.gep.2, align 8

%megastruct.gep.3 = getelementptr inbounds i8, ptr %megastruct, i64 24
store i64 %4, ptr %megastruct.gep.3, align 8

%megastruct.gep.4 = getelementptr inbounds i8, ptr %megastruct, i64 32
store ptr %5, ptr %megastruct.gep.4, align 8

%megastruct.gep.5 = getelementptr inbounds i8, ptr %megastruct, i64 40
store i64 %6, ptr %megastruct.gep.5, align 8

call fastcc void @callee2(ptr %megastruct)
ret i64 1
}

define i64 @caller() local_unnamed_addr {
; CHECK-LABEL: define i64 @caller() local_unnamed_addr {
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @callee()
; CHECK-NEXT: ret i64 1
;
%1 = alloca { ptr, i64 }, align 8
%2 = alloca { ptr, i64 }, align 8

store ptr @sudoku0, ptr %1, align 8
%.gep0 = getelementptr inbounds i8, ptr %1, i64 8
store i64 4, ptr %.gep0, align 8

store ptr @sudoku1, ptr %2, align 8
%.gep1 = getelementptr inbounds i8, ptr %2, i64 8
store i64 4, ptr %.gep1, align 8

%p = call i64 @callee(ptr nonnull %1, ptr nonnull %2)
ret i64 %p
}

define i64 @m() local_unnamed_addr {
; CHECK-LABEL: define i64 @m() local_unnamed_addr {
; CHECK-NEXT: [[TMP1:%.*]] = call i64 @caller()
; CHECK-NEXT: ret i64 1
;
%1 = call i64 @caller()
ret i64 %1
}