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enhance isRemovable to refuse to delete volatile mem transfers

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now that DSE hacks on them.  This fixes a regression I introduced,
by generalizing DSE to hack on transfers.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120445 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-11-30 19:12:10 +00:00
parent 12822af16a
commit 55ee75d571
2 changed files with 35 additions and 8 deletions
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23
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -152,12 +152,27 @@ getLocForWrite(Instruction *Inst, AliasAnalysis &AA) {
/// isRemovable - If the value of this instruction and the memory it writes to
/// is unused, may we delete this instruction?
static bool isRemovable(Instruction *I) {
assert(hasMemoryWrite(I));
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
return II->getIntrinsicID() != Intrinsic::lifetime_end;
// Don't remove volatile stores.
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return !SI->isVolatile();
return true;
IntrinsicInst *II = cast<IntrinsicInst>(I);
switch (II->getIntrinsicID()) {
default: assert(0 && "doesn't pass 'hasMemoryWrite' predicate");
case Intrinsic::lifetime_end:
// Never remove dead lifetime_end's, e.g. because it is followed by a
// free.
return false;
case Intrinsic::init_trampoline:
// Always safe to remove init_trampoline.
return true;
case Intrinsic::memset:
case Intrinsic::memmove:
case Intrinsic::memcpy:
// Don't remove volatile memory intrinsics.
return !cast<MemIntrinsic>(II)->isVolatile();
}
}
/// getPointerOperand - Return the pointer that is being written to.

20
test/Transforms/DeadStoreElimination/simple.ll
View File

@ -1,6 +1,12 @@
; RUN: opt < %s -basicaa -dse -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"
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
declare void @llvm.memset.i64(i8*, i8, i64, i32)
declare void @llvm.memcpy.i64(i8*, i8*, i64, i32)
declare i8* @llvm.init.trampoline(i8*, i8*, i8*)
define void @test1(i32* %Q, i32* %P) {
%DEAD = load i32* %Q
store i32 %DEAD, i32* %P
@ -55,9 +61,6 @@ define void @test5(i32* %Q) {
; CHECK-NEXT: ret void
}
declare void @llvm.memset.i64(i8*, i8, i64, i32)
declare void @llvm.memcpy.i64(i8*, i8*, i64, i32)
; Should delete store of 10 even though memset is a may-store to P (P and Q may
; alias).
define void @test6(i32 *%p, i8 *%q) {
@ -116,7 +119,6 @@ define double @test10(i8* %X) {
; DSE should delete the dead trampoline.
declare i8* @llvm.init.trampoline(i8*, i8*, i8*)
declare void @test11f()
define void @test11() {
; CHECK: @test11
@ -210,3 +212,13 @@ define void @test17(i8* %P, i8* %Q) nounwind ssp {
; CHECK-NEXT: ret
}
; Should not delete the volatile memset.
define void @test17v(i8* %P, i8* %Q) nounwind ssp {
tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 true)
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
ret void
; CHECK: @test17v
; CHECK-NEXT: call void @llvm.memset
; CHECK-NEXT: call void @llvm.memcpy
; CHECK-NEXT: ret
}