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[DSE] Transform memset + malloc --> calloc (PR25892) 

After this change DSE can eliminate malloc + memset and emit calloc.
It's https://reviews.llvm.org/D101440 follow-up.

Differential Revision: https://reviews.llvm.org/D103009
This commit is contained in:
Dawid Jurczak 2021-07-05 11:42:17 +02:00
parent 5f08219322
commit 43234b1595
2 changed files with 188 additions and 14 deletions
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78
llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -56,6 +56,7 @@
#include "llvm/IR/DataLayout.h" #include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h" #include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h" #include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h" #include "llvm/IR/InstIterator.h"
#include "llvm/IR/InstrTypes.h" #include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h" #include "llvm/IR/Instruction.h"
@ -78,6 +79,7 @@
#include "llvm/Support/raw_ostream.h" #include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h" #include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/AssumeBundleBuilder.h" #include "llvm/Transforms/Utils/AssumeBundleBuilder.h"
#include "llvm/Transforms/Utils/BuildLibCalls.h"
#include "llvm/Transforms/Utils/Local.h" #include "llvm/Transforms/Utils/Local.h"
#include <algorithm> #include <algorithm>
#include <cassert> #include <cassert>
@ -505,7 +507,12 @@ memoryIsNotModifiedBetween(Instruction *FirstI, Instruction *SecondI,
BasicBlock::iterator SecondBBI(SecondI); BasicBlock::iterator SecondBBI(SecondI);
BasicBlock *FirstBB = FirstI->getParent(); BasicBlock *FirstBB = FirstI->getParent();
BasicBlock *SecondBB = SecondI->getParent(); BasicBlock *SecondBB = SecondI->getParent();
MemoryLocation MemLoc = MemoryLocation::get(SecondI); MemoryLocation MemLoc;
if (auto *MemSet = dyn_cast<MemSetInst>(SecondI))
MemLoc = MemoryLocation::getForDest(MemSet);
else
MemLoc = MemoryLocation::get(SecondI);
auto *MemLocPtr = const_cast<Value *>(MemLoc.Ptr); auto *MemLocPtr = const_cast<Value *>(MemLoc.Ptr);
// Start checking the SecondBB. // Start checking the SecondBB.
@ -819,14 +826,17 @@ bool isNoopIntrinsic(Instruction *I) {
} }
// Check if we can ignore \p D for DSE. // Check if we can ignore \p D for DSE.
bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller) { bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller,
const TargetLibraryInfo &TLI) {
Instruction *DI = D->getMemoryInst(); Instruction *DI = D->getMemoryInst();
// Calls that only access inaccessible memory cannot read or write any memory // Calls that only access inaccessible memory cannot read or write any memory
// locations we consider for elimination. // locations we consider for elimination.
if (auto *CB = dyn_cast<CallBase>(DI)) if (auto *CB = dyn_cast<CallBase>(DI))
if (CB->onlyAccessesInaccessibleMemory()) if (CB->onlyAccessesInaccessibleMemory()) {
if (isAllocLikeFn(DI, &TLI))
return false;
return true; return true;
}
// We can eliminate stores to locations not visible to the caller across // We can eliminate stores to locations not visible to the caller across
// throwing instructions. // throwing instructions.
if (DI->mayThrow() && !DefVisibleToCaller) if (DI->mayThrow() && !DefVisibleToCaller)
@ -841,7 +851,7 @@ bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller) {
return true; return true;
// Skip intrinsics that do not really read or modify memory. // Skip intrinsics that do not really read or modify memory.
if (isNoopIntrinsic(D->getMemoryInst())) if (isNoopIntrinsic(DI))
return true; return true;
return false; return false;
@ -1389,7 +1399,7 @@ struct DSEState {
MemoryDef *CurrentDef = cast<MemoryDef>(Current); MemoryDef *CurrentDef = cast<MemoryDef>(Current);
Instruction *CurrentI = CurrentDef->getMemoryInst(); Instruction *CurrentI = CurrentDef->getMemoryInst();
if (canSkipDef(CurrentDef, !isInvisibleToCallerBeforeRet(DefUO))) if (canSkipDef(CurrentDef, !isInvisibleToCallerBeforeRet(DefUO), TLI))
continue; continue;
// Before we try to remove anything, check for any extra throwing // Before we try to remove anything, check for any extra throwing
@ -1816,13 +1826,55 @@ struct DSEState {
if (StoredConstant && StoredConstant->isNullValue()) { if (StoredConstant && StoredConstant->isNullValue()) {
auto *DefUOInst = dyn_cast<Instruction>(DefUO); auto *DefUOInst = dyn_cast<Instruction>(DefUO);
if (DefUOInst && isCallocLikeFn(DefUOInst, &TLI)) { if (DefUOInst) {
auto *UnderlyingDef = cast<MemoryDef>(MSSA.getMemoryAccess(DefUOInst)); if (isCallocLikeFn(DefUOInst, &TLI)) {
// If UnderlyingDef is the clobbering access of Def, no instructions auto *UnderlyingDef =
// between them can modify the memory location. cast<MemoryDef>(MSSA.getMemoryAccess(DefUOInst));
auto *ClobberDef = // If UnderlyingDef is the clobbering access of Def, no instructions
MSSA.getSkipSelfWalker()->getClobberingMemoryAccess(Def); // between them can modify the memory location.
return UnderlyingDef == ClobberDef; auto *ClobberDef =
MSSA.getSkipSelfWalker()->getClobberingMemoryAccess(Def);
return UnderlyingDef == ClobberDef;
}
if (MemSet) {
if (F.hasFnAttribute(Attribute::SanitizeMemory))
return false;
auto *Malloc = const_cast<CallInst *>(dyn_cast<CallInst>(DefUOInst));
if (!Malloc)
return false;
auto *InnerCallee = Malloc->getCalledFunction();
if (!InnerCallee)
return false;
LibFunc Func;
if (!TLI.getLibFunc(*InnerCallee, Func) || !TLI.has(Func) ||
Func != LibFunc_malloc)
return false;
if (Malloc->getOperand(0) == MemSet->getLength()) {
if (DT.dominates(Malloc, MemSet) &&
memoryIsNotModifiedBetween(Malloc, MemSet, BatchAA, DL, &DT)) {
IRBuilder<> IRB(Malloc);
const auto &DL = Malloc->getModule()->getDataLayout();
AttributeList EmptyList;
if (auto *Calloc = emitCalloc(
ConstantInt::get(IRB.getIntPtrTy(DL), 1),
Malloc->getArgOperand(0), EmptyList, IRB, TLI)) {
MemorySSAUpdater Updater(&MSSA);
auto *LastDef = cast<MemoryDef>(
Updater.getMemorySSA()->getMemoryAccess(Malloc));
auto *NewAccess = Updater.createMemoryAccessAfter(
cast<Instruction>(Calloc), LastDef, LastDef);
auto *NewAccessMD = cast<MemoryDef>(NewAccess);
Updater.insertDef(NewAccessMD, /*RenameUses=*/true);
Updater.removeMemoryAccess(Malloc);
Malloc->replaceAllUsesWith(Calloc);
Malloc->eraseFromParent();
return true;
}
return false;
}
}
}
} }
} }

124
llvm/test/Transforms/DeadStoreElimination/noop-stores.ll
View File

@ -1,6 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -basic-aa -dse -S | FileCheck %s ; RUN: opt < %s -basic-aa -dse -S | FileCheck %s
; RUN: opt < %s -aa-pipeline=basic-aa -passes=dse -S | FileCheck %s ; RUN: opt < %s -aa-pipeline=basic-aa -passes='dse,verify<memoryssa>' -S | FileCheck %s
target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128" target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
declare i8* @calloc(i64, i64) declare i8* @calloc(i64, i64)
@ -309,6 +309,128 @@ entry:
ret void ret void
} }
declare noalias i8* @malloc(i64)
declare noalias i8* @_Znwm(i64)
declare void @clobber_memory(float*)
; based on pr25892_lite
define i8* @zero_memset_after_malloc(i64 %size) {
; CHECK-LABEL: @zero_memset_after_malloc(
; CHECK-NEXT: [[CALL:%.*]] = call i8* @calloc(i64 1, i64 [[SIZE:%.*]])
; CHECK-NEXT: ret i8* [[CALL]]
;
%call = call i8* @malloc(i64 %size) inaccessiblememonly
call void @llvm.memset.p0i8.i64(i8* %call, i8 0, i64 %size, i1 false)
ret i8* %call
}
; based on pr25892_lite
define i8* @zero_memset_after_malloc_with_intermediate_clobbering(i64 %size) {
; CHECK-LABEL: @zero_memset_after_malloc_with_intermediate_clobbering(
; CHECK-NEXT: [[CALL:%.*]] = call i8* @malloc(i64 [[SIZE:%.*]])
; CHECK-NEXT: [[BC:%.*]] = bitcast i8* [[CALL]] to float*
; CHECK-NEXT: call void @clobber_memory(float* [[BC]])
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[CALL]], i8 0, i64 [[SIZE]], i1 false)
; CHECK-NEXT: ret i8* [[CALL]]
;
%call = call i8* @malloc(i64 %size) inaccessiblememonly
%bc = bitcast i8* %call to float*
call void @clobber_memory(float* %bc)
call void @llvm.memset.p0i8.i64(i8* %call, i8 0, i64 %size, i1 false)
ret i8* %call
}
; based on pr25892_lite
define i8* @zero_memset_after_malloc_with_different_sizes(i64 %size) {
; CHECK-LABEL: @zero_memset_after_malloc_with_different_sizes(
; CHECK-NEXT: [[CALL:%.*]] = call i8* @malloc(i64 [[SIZE:%.*]])
; CHECK-NEXT: [[SIZE2:%.*]] = add nsw i64 [[SIZE]], -1
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[CALL]], i8 0, i64 [[SIZE2]], i1 false)
; CHECK-NEXT: ret i8* [[CALL]]
;
%call = call i8* @malloc(i64 %size) inaccessiblememonly
%size2 = add nsw i64 %size, -1
call void @llvm.memset.p0i8.i64(i8* %call, i8 0, i64 %size2, i1 false)
ret i8* %call
}
; based on pr25892_lite
define i8* @zero_memset_after_new(i64 %size) {
; CHECK-LABEL: @zero_memset_after_new(
; CHECK-NEXT: [[CALL:%.*]] = call i8* @_Znwm(i64 [[SIZE:%.*]])
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[CALL]], i8 0, i64 [[SIZE]], i1 false)
; CHECK-NEXT: ret i8* [[CALL]]
;
%call = call i8* @_Znwm(i64 %size)
call void @llvm.memset.p0i8.i64(i8* %call, i8 0, i64 %size, i1 false)
ret i8* %call
}
; This should not create a calloc and should not crash the compiler.
define i8* @notmalloc_memset(i64 %size, i8*(i64)* %notmalloc) {
; CHECK-LABEL: @notmalloc_memset(
; CHECK-NEXT: [[CALL1:%.*]] = call i8* [[NOTMALLOC:%.*]](i64 [[SIZE:%.*]])
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[CALL1]], i8 0, i64 [[SIZE]], i1 false)
; CHECK-NEXT: ret i8* [[CALL1]]
;
%call1 = call i8* %notmalloc(i64 %size)
call void @llvm.memset.p0i8.i64(i8* %call1, i8 0, i64 %size, i1 false)
ret i8* %call1
}
define float* @pr25892(i64 %size) {
; CHECK-LABEL: @pr25892(
; CHECK: entry:
; CHECK-NEXT: [[CALL:%.*]] = call i8* @calloc(i64 1, i64 [[SIZE:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8* [[CALL]], null
; CHECK-NEXT: br i1 [[CMP]], label [[CLEANUP:%.*]], label [[IF_END:%.*]]
; CHECK: if.end:
; CHECK-NEXT: [[BC:%.*]] = bitcast i8* [[CALL]] to float*
; CHECK-NEXT: br label [[CLEANUP]]
; CHECK: cleanup:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi float* [ [[BC]], [[IF_END]] ], [ null, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret float* [[RETVAL_0]]
;
entry:
%call = call i8* @malloc(i64 %size) inaccessiblememonly
%cmp = icmp eq i8* %call, null
br i1 %cmp, label %cleanup, label %if.end
if.end:
%bc = bitcast i8* %call to float*
call void @llvm.memset.p0i8.i64(i8* %call, i8 0, i64 %size, i1 false)
br label %cleanup
cleanup:
%retval.0 = phi float* [ %bc, %if.end ], [ null, %entry ]
ret float* %retval.0
}
; CHECK-LABEL: @pr25892_with_extra_store(
; CHECK: entry:
; CHECK-NEXT: [[CALL:%.*]] = call i8* @calloc(i64 1, i64 [[SIZE:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8* [[CALL]], null
; CHECK-NEXT: br i1 [[CMP]], label [[CLEANUP:%.*]], label [[IF_END:%.*]]
; CHECK: if.end:
; CHECK-NEXT: [[BC:%.*]] = bitcast i8* [[CALL]] to float*
; CHECK-NEXT: br label [[CLEANUP]]
; CHECK: cleanup:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi float* [ [[BC]], [[IF_END]] ], [ null, [[ENTRY:%.*]] ]
; CHECK-NEXT: ret float* [[RETVAL_0]]
;
define float* @pr25892_with_extra_store(i64 %size) {
entry:
%call = call i8* @malloc(i64 %size) inaccessiblememonly
%cmp = icmp eq i8* %call, null
br i1 %cmp, label %cleanup, label %if.end
if.end:
%bc = bitcast i8* %call to float*
call void @llvm.memset.p0i8.i64(i8* %call, i8 0, i64 %size, i1 false)
store i8 0, i8* %call, align 1
br label %cleanup
cleanup:
%retval.0 = phi float* [ %bc, %if.end ], [ null, %entry ]
ret float* %retval.0
}
; PR50143 ; PR50143
define i8* @store_zero_after_calloc_inaccessiblememonly() { define i8* @store_zero_after_calloc_inaccessiblememonly() {
; CHECK-LABEL: @store_zero_after_calloc_inaccessiblememonly( ; CHECK-LABEL: @store_zero_after_calloc_inaccessiblememonly(