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[CUDA, MemCpyOpt] Add a flag to force-enable memcpyopt and use it for CUDA. 

Attempt to enable MemCpyOpt unconditionally in D104801 uncovered the fact that
there are users that do not expect LLVM to materialize `memset` intrinsic.

While other passes can do that, too, MemCpyOpt triggers it more frequently and
breaks sanitizers and some downstream users.

For now introduce a flag to force-enable the flag and opt-in only CUDA
compilation with NVPTX back-end.

Differential Revision: https://reviews.llvm.org/D106401
This commit is contained in:
Artem Belevich 2021-07-20 14:37:06 -07:00
parent f59f659879
commit 6a9cf21f5a
3 changed files with 12 additions and 4 deletions
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3
clang/lib/Driver/ToolChains/Cuda.cpp
View File

@ -685,7 +685,8 @@ void CudaToolChain::addClangTargetOptions(
"Only OpenMP or CUDA offloading kinds are supported for NVIDIA GPUs.");
if (DeviceOffloadingKind == Action::OFK_Cuda) {
CC1Args.push_back("-fcuda-is-device");
CC1Args.append(
{"-fcuda-is-device", "-mllvm", "-enable-memcpyopt-without-libcalls"});
if (DriverArgs.hasFlag(options::OPT_fcuda_approx_transcendentals,
options::OPT_fno_cuda_approx_transcendentals, false))

11
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -67,6 +67,10 @@ using namespace llvm;
#define DEBUG_TYPE "memcpyopt"
static cl::opt<bool> EnableMemCpyOptWithoutLibcalls(
"enable-memcpyopt-without-libcalls", cl::init(false), cl::Hidden,
cl::desc("Enable memcpyopt even when libcalls are disabled"));
static cl::opt<bool>
EnableMemorySSA("enable-memcpyopt-memoryssa", cl::init(true), cl::Hidden,
cl::desc("Use MemorySSA-backed MemCpyOpt."));
@ -677,8 +681,9 @@ bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
// the corresponding libcalls are not available.
// TODO: We should really distinguish between libcall availability and
// our ability to introduce intrinsics.
if (T->isAggregateType() && TLI->has(LibFunc_memcpy) &&
TLI->has(LibFunc_memmove)) {
if (T->isAggregateType() &&
(EnableMemCpyOptWithoutLibcalls ||
(TLI->has(LibFunc_memcpy) && TLI->has(LibFunc_memmove)))) {
MemoryLocation LoadLoc = MemoryLocation::get(LI);
// We use alias analysis to check if an instruction may store to
@ -806,7 +811,7 @@ bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
// this if the corresponding libfunc is not available.
// TODO: We should really distinguish between libcall availability and
// our ability to introduce intrinsics.
if (!TLI->has(LibFunc_memset))
if (!(TLI->has(LibFunc_memset) || EnableMemCpyOptWithoutLibcalls))
return false;
// There are two cases that are interesting for this code to handle: memcpy

2
llvm/test/Transforms/MemCpyOpt/no-libcalls.ll
View File

@ -1,6 +1,8 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -memcpyopt < %s | FileCheck %s --check-prefixes=CHECK,LIBCALLS
; RUN: opt -S -memcpyopt -mtriple=amdgcn-- < %s | FileCheck %s --check-prefixes=CHECK,NO-LIBCALLS
; RUN: opt -S -memcpyopt -mtriple=amdgcn-- -enable-memcpyopt-without-libcalls < %s \
; RUN: | FileCheck %s --check-prefixes=CHECK,LIBCALLS
; REQUIRES: amdgpu-registered-target