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teach instcombine to remove allocated buffers even if there are stores, memcpy/memmove/memset, and objectsize users.

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This means we can do cheap DSE for heap memory.
Nothing is done if the pointer excapes or has a load.

The churn in the tests is mostly due to objectsize, since we want to make sure we
don't delete the malloc call before evaluating the objectsize (otherwise it becomes -1/0)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159876 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nuno Lopes 2012-07-06 23:09:25 +00:00
parent eb54603ddd
commit 9969458b16
6 changed files with 128 additions and 17 deletions
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27
lib/Transforms/InstCombine/InstructionCombining.cpp
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@ -1137,12 +1137,29 @@ static bool IsOnlyNullComparedAndFreed(Value *V, SmallVectorImpl<WeakVH> &Users,
}
}
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) {
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end) {
switch (II->getIntrinsicID()) {
default: return false;
case Intrinsic::memmove:
case Intrinsic::memcpy:
case Intrinsic::memset: {
MemIntrinsic *MI = cast<MemIntrinsic>(II);
if (MI->isVolatile() || MI->getRawDest() != V)
return false;
}
// fall through
case Intrinsic::objectsize:
case Intrinsic::lifetime_start:
case Intrinsic::lifetime_end:
Users.push_back(II);
continue;
}
}
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (SI->isVolatile() || SI->getPointerOperand() != V)
return false;
Users.push_back(SI);
continue;
}
return false;
}
return true;
@ -1164,6 +1181,12 @@ Instruction *InstCombiner::visitMalloc(Instruction &MI) {
C->isFalseWhenEqual()));
} else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) {
ReplaceInstUsesWith(*I, UndefValue::get(I->getType()));
} else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
if (II->getIntrinsicID() == Intrinsic::objectsize) {
ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1));
uint64_t DontKnow = CI->isZero() ? -1ULL : 0;
ReplaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow));
}
}
EraseInstFromFunction(*I);
}

23
test/Transforms/InstCombine/badmalloc.ll
View File

@ -16,5 +16,26 @@ define i1 @test1() {
ret i1 %B
; CHECK: @test1
; CHECK: ret i1 %B
; CHECK: ret i1 false
}
; CHECK: @test2
define noalias i8* @test2() nounwind {
entry:
; CHECK: @malloc
%A = call noalias i8* @malloc(i64 4) nounwind
; CHECK: icmp eq
%tobool = icmp eq i8* %A, null
; CHECK: br i1
br i1 %tobool, label %return, label %if.end
if.end:
; CHECK: store
store i8 7, i8* %A
br label %return
return:
; CHECK: phi
%retval.0 = phi i8* [ %A, %if.end ], [ null, %entry ]
ret i8* %retval.0
}

18
test/Transforms/InstCombine/invoke.ll
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@ -4,6 +4,7 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3
declare i32 @__gxx_personality_v0(...)
declare void @__cxa_call_unexpected(i8*)
declare i64 @llvm.objectsize.i64(i8*, i1) nounwind readonly
declare i8* @_Znwm(i64)
; CHECK: @f1
@ -45,3 +46,20 @@ lpad:
tail call void @__cxa_call_unexpected(i8* %2) noreturn nounwind
unreachable
}
; CHECK: @f3
define void @f3() nounwind uwtable ssp {
; CHECK: invoke void @llvm.donothing()
%call = invoke noalias i8* @_Znwm(i64 13)
to label %invoke.cont unwind label %lpad
invoke.cont:
ret void
lpad:
%1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
filter [0 x i8*] zeroinitializer
%2 = extractvalue { i8*, i32 } %1, 0
tail call void @__cxa_call_unexpected(i8* %2) noreturn nounwind
unreachable
}

53
test/Transforms/InstCombine/malloc-free-delete.ll
View File

@ -1,17 +1,17 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
; PR1201
define i32 @main(i32 %argc, i8** %argv) {
; CHECK: @main
%c_19 = alloca i8*
%malloc_206 = tail call i8* @malloc(i32 mul (i32 ptrtoint (i8* getelementptr (i8* null, i32 1) to i32), i32 10))
store i8* %malloc_206, i8** %c_19
%tmp_207 = load i8** %c_19
tail call void @free(i8* %tmp_207)
ret i32 0
; CHECK-NOT: malloc
; CHECK-NOT: free
; CHECK: ret i32 0
; CHECK-NEXT: ret i32 0
}
declare noalias i8* @calloc(i32, i32) nounwind
declare noalias i8* @malloc(i32)
declare void @free(i8*)
@ -26,13 +26,24 @@ define i1 @foo() {
declare void @llvm.lifetime.start(i64, i8*)
declare void @llvm.lifetime.end(i64, i8*)
declare i64 @llvm.objectsize.i64(i8*, i1)
declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind
declare void @llvm.memmove.p0i8.p0i8.i32(i8* nocapture, i8* nocapture, i32, i32, i1) nounwind
declare void @llvm.memset.p0i8.i32(i8*, i8, i32, i32, i1) nounwind
define void @test3() {
define void @test3(i8* %src) {
; CHECK: @test3
; CHECK-NEXT: ret void
%a = call noalias i8* @malloc(i32 10)
call void @llvm.lifetime.start(i64 10, i8* %a)
call void @llvm.lifetime.end(i64 10, i8* %a)
%size = call i64 @llvm.objectsize.i64(i8* %a, i1 true)
store i8 42, i8* %a
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %a, i8* %src, i32 32, i32 1, i1 false)
call void @llvm.memmove.p0i8.p0i8.i32(i8* %a, i8* %src, i32 32, i32 1, i1 false)
call void @llvm.memset.p0i8.i32(i8* %a, i8 5, i32 32, i32 1, i1 false)
%alloc2 = call noalias i8* @calloc(i32 5, i32 7) nounwind
%z = icmp ne i8* %alloc2, null
ret void
}
@ -46,3 +57,37 @@ define void @test4() {
call void @free(i8* %C)
ret void
}
; CHECK: @test5
define void @test5(i8* %ptr, i8** %esc) {
; CHECK-NEXT: call i8* @malloc
; CHECK-NEXT: call i8* @malloc
; CHECK-NEXT: call i8* @malloc
; CHECK-NEXT: call i8* @malloc
; CHECK-NEXT: call i8* @malloc
; CHECK-NEXT: call i8* @malloc
; CHECK-NEXT: call i8* @malloc
; CHECK-NEXT: call void @llvm.memcpy
; CHECK-NEXT: call void @llvm.memmove
; CHECK-NEXT: store
; CHECK-NEXT: call void @llvm.memcpy
; CHECK-NEXT: call void @llvm.memmove
; CHECK-NEXT: call void @llvm.memset
; CHECK-NEXT: store volatile
; CHECK-NEXT: ret
%a = call i8* @malloc(i32 700)
%b = call i8* @malloc(i32 700)
%c = call i8* @malloc(i32 700)
%d = call i8* @malloc(i32 700)
%e = call i8* @malloc(i32 700)
%f = call i8* @malloc(i32 700)
%g = call i8* @malloc(i32 700)
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %ptr, i8* %a, i32 32, i32 1, i1 false)
call void @llvm.memmove.p0i8.p0i8.i32(i8* %ptr, i8* %b, i32 32, i32 1, i1 false)
store i8* %c, i8** %esc
call void @llvm.memcpy.p0i8.p0i8.i32(i8* %d, i8* %ptr, i32 32, i32 1, i1 true)
call void @llvm.memmove.p0i8.p0i8.i32(i8* %e, i8* %ptr, i32 32, i32 1, i1 true)
call void @llvm.memset.p0i8.i32(i8* %f, i8 5, i32 32, i32 1, i1 true)
store volatile i8 4, i8* %g
ret void
}

10
test/Transforms/InstCombine/objsize-64.ll
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@ -8,23 +8,25 @@ declare void @__cxa_call_unexpected(i8*)
declare i64 @llvm.objectsize.i64(i8*, i1) nounwind readonly
; CHECK: @f1
define i64 @f1() {
define i64 @f1(i8 **%esc) {
%call = call i8* @malloc(i32 4)
store i8* %call, i8** %esc
%size = call i64 @llvm.objectsize.i64(i8* %call, i1 false)
; CHECK-NEXT: ret i64 4
; CHECK: ret i64 4
ret i64 %size
}
; CHECK: @f2
define i64 @f2() nounwind uwtable ssp {
define i64 @f2(i8** %esc) nounwind uwtable ssp {
entry:
; CHECK: invoke void @llvm.donothing()
; CHECK: invoke noalias i8* @_Znwm(i64 13)
%call = invoke noalias i8* @_Znwm(i64 13)
to label %invoke.cont unwind label %lpad
invoke.cont:
; CHECK: ret i64 13
store i8* %call, i8** %esc
%0 = tail call i64 @llvm.objectsize.i64(i8* %call, i1 false)
ret i64 %0

14
test/Transforms/InstCombine/objsize.ll
View File

@ -121,7 +121,7 @@ entry:
; rdar://7782496
@s = external global i8*
define void @test5(i32 %n) nounwind ssp {
define i8* @test5(i32 %n) nounwind ssp {
; CHECK: @test5
entry:
%0 = tail call noalias i8* @malloc(i32 20) nounwind
@ -130,7 +130,7 @@ entry:
; CHECK-NOT: @llvm.objectsize
; CHECK: @llvm.memcpy.p0i8.p0i8.i32(i8* %0, i8* %1, i32 10, i32 1, i1 false)
%3 = tail call i8* @__memcpy_chk(i8* %0, i8* %2, i32 10, i32 %1) nounwind
ret void
ret i8* %0
}
define void @test6(i32 %n) nounwind ssp {
@ -149,22 +149,24 @@ declare i8* @__memset_chk(i8*, i32, i32, i32) nounwind
declare noalias i8* @malloc(i32) nounwind
define i32 @test7() {
define i32 @test7(i8** %esc) {
; CHECK: @test7
%alloc = call noalias i8* @malloc(i32 48) nounwind
store i8* %alloc, i8** %esc
%gep = getelementptr inbounds i8* %alloc, i32 16
%objsize = call i32 @llvm.objectsize.i32(i8* %gep, i1 false) nounwind readonly
; CHECK-NEXT: ret i32 32
; CHECK: ret i32 32
ret i32 %objsize
}
declare noalias i8* @calloc(i32, i32) nounwind
define i32 @test8() {
define i32 @test8(i8** %esc) {
; CHECK: @test8
%alloc = call noalias i8* @calloc(i32 5, i32 7) nounwind
store i8* %alloc, i8** %esc
%gep = getelementptr inbounds i8* %alloc, i32 5
%objsize = call i32 @llvm.objectsize.i32(i8* %gep, i1 false) nounwind readonly
; CHECK-NEXT: ret i32 30
; CHECK: ret i32 30
ret i32 %objsize
}