[llvm] [Intrinsics][PreISelInstrinsicLowering] llvm.memcpy.inline length no longer needs to be constant (PR #98281)
Alex Bradbury via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 10 01:09:49 PDT 2024
https://github.com/asb created https://github.com/llvm/llvm-project/pull/98281
Following on from the discussion in
https://discourse.llvm.org/t/rfc-introducing-an-llvm-memset-pattern-inline-intrinsic/79496 and the equivalent change for llvm.memset.inline (#95397), this removes the requirement that the length of llvm.memcpy.inline is constant. PreISelInstrinsicLowering will expand llvm.memcpy.inline with non-constant lengths, while the codegen path for constant lengths is left unaltered.
>From dc76029dcd38f1d473627c58ad588250e1ea4829 Mon Sep 17 00:00:00 2001
From: Alex Bradbury <asb at igalia.com>
Date: Wed, 10 Jul 2024 09:06:50 +0100
Subject: [PATCH] [Intrinsics][PreISelInstrinsicLowering] llvm.memcpy.inline
length no longer needs to be constant
Following on from the discussion in
https://discourse.llvm.org/t/rfc-introducing-an-llvm-memset-pattern-inline-intrinsic/79496
and the equivalent change for llvm.memset.inline (#95397), this removes
the requirement that the length of llvm.memcpy.inline is constant.
PreISelInstrinsicLowering will expand llvm.memcpy.inline with
non-constant lengths, while the codegen path for constant lengths is
left unaltered.
---
llvm/docs/LangRef.rst | 2 +-
llvm/include/llvm/IR/IntrinsicInst.h | 3 --
llvm/include/llvm/IR/Intrinsics.td | 3 +-
llvm/lib/Analysis/Lint.cpp | 20 ++---------
llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp | 16 +++++++++
.../X86/memcpy-inline-non-constant-len.ll | 34 +++++++++++++++++++
llvm/test/Verifier/intrinsic-immarg.ll | 8 -----
7 files changed, 54 insertions(+), 32 deletions(-)
create mode 100644 llvm/test/Transforms/PreISelIntrinsicLowering/X86/memcpy-inline-non-constant-len.ll
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index ae39217dc8ff8..21ded802ebdf0 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -15026,7 +15026,7 @@ Arguments:
""""""""""
The first argument is a pointer to the destination, the second is a
-pointer to the source. The third argument is a constant integer argument
+pointer to the source. The third argument is an integer argument
specifying the number of bytes to copy, and the fourth is a
boolean indicating a volatile access.
diff --git a/llvm/include/llvm/IR/IntrinsicInst.h b/llvm/include/llvm/IR/IntrinsicInst.h
index a2ecf625ff61a..fe3f92da400f8 100644
--- a/llvm/include/llvm/IR/IntrinsicInst.h
+++ b/llvm/include/llvm/IR/IntrinsicInst.h
@@ -1296,9 +1296,6 @@ class MemMoveInst : public MemTransferInst {
/// This class wraps the llvm.memcpy.inline intrinsic.
class MemCpyInlineInst : public MemCpyInst {
public:
- ConstantInt *getLength() const {
- return cast<ConstantInt>(MemCpyInst::getLength());
- }
// Methods for support type inquiry through isa, cast, and dyn_cast:
static bool classof(const IntrinsicInst *I) {
return I->getIntrinsicID() == Intrinsic::memcpy_inline;
diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
index 65a9b68b5229d..615ece332a1d6 100644
--- a/llvm/include/llvm/IR/Intrinsics.td
+++ b/llvm/include/llvm/IR/Intrinsics.td
@@ -966,7 +966,6 @@ def int_memcpy : Intrinsic<[],
// Memcpy semantic that is guaranteed to be inlined.
// In particular this means that the generated code is not allowed to call any
// external function.
-// The third argument (specifying the size) must be a constant.
def int_memcpy_inline
: Intrinsic<[],
[llvm_anyptr_ty, llvm_anyptr_ty, llvm_anyint_ty, llvm_i1_ty],
@@ -974,7 +973,7 @@ def int_memcpy_inline
NoCapture<ArgIndex<0>>, NoCapture<ArgIndex<1>>,
NoAlias<ArgIndex<0>>, NoAlias<ArgIndex<1>>,
WriteOnly<ArgIndex<0>>, ReadOnly<ArgIndex<1>>,
- ImmArg<ArgIndex<2>>, ImmArg<ArgIndex<3>>]>;
+ ImmArg<ArgIndex<3>>]>;
def int_memmove : Intrinsic<[],
[llvm_anyptr_ty, llvm_anyptr_ty, llvm_anyint_ty,
diff --git a/llvm/lib/Analysis/Lint.cpp b/llvm/lib/Analysis/Lint.cpp
index 496308a0c247a..a44d5a3bbe462 100644
--- a/llvm/lib/Analysis/Lint.cpp
+++ b/llvm/lib/Analysis/Lint.cpp
@@ -290,7 +290,8 @@ void Lint::visitCallBase(CallBase &I) {
// TODO: Check more intrinsics
- case Intrinsic::memcpy: {
+ case Intrinsic::memcpy:
+ case Intrinsic::memcpy_inline: {
MemCpyInst *MCI = cast<MemCpyInst>(&I);
visitMemoryReference(I, MemoryLocation::getForDest(MCI),
MCI->getDestAlign(), nullptr, MemRef::Write);
@@ -311,23 +312,6 @@ void Lint::visitCallBase(CallBase &I) {
"Undefined behavior: memcpy source and destination overlap", &I);
break;
}
- case Intrinsic::memcpy_inline: {
- MemCpyInlineInst *MCII = cast<MemCpyInlineInst>(&I);
- const uint64_t Size = MCII->getLength()->getValue().getLimitedValue();
- visitMemoryReference(I, MemoryLocation::getForDest(MCII),
- MCII->getDestAlign(), nullptr, MemRef::Write);
- visitMemoryReference(I, MemoryLocation::getForSource(MCII),
- MCII->getSourceAlign(), nullptr, MemRef::Read);
-
- // Check that the memcpy arguments don't overlap. The AliasAnalysis API
- // isn't expressive enough for what we really want to do. Known partial
- // overlap is not distinguished from the case where nothing is known.
- const LocationSize LS = LocationSize::precise(Size);
- Check(AA->alias(MCII->getSource(), LS, MCII->getDest(), LS) !=
- AliasResult::MustAlias,
- "Undefined behavior: memcpy source and destination overlap", &I);
- break;
- }
case Intrinsic::memmove: {
MemMoveInst *MMI = cast<MemMoveInst>(&I);
visitMemoryReference(I, MemoryLocation::getForDest(MMI),
diff --git a/llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp b/llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp
index 8572cdc160456..19950f3eb67ba 100644
--- a/llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp
+++ b/llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp
@@ -230,6 +230,21 @@ bool PreISelIntrinsicLowering::expandMemIntrinsicUses(Function &F) const {
break;
}
+ case Intrinsic::memcpy_inline: {
+ // Only expand llvm.memcpy.inline with non-constant length in this
+ // codepath, leaving the current SelectionDAG expansion for constant
+ // length memcpy intrinsics undisturbed.
+ auto *Memcpy = cast<MemCpyInlineInst>(Inst);
+ if (isa<ConstantInt>(Memcpy->getLength()))
+ break;
+
+ Function *ParentFunc = Memcpy->getFunction();
+ const TargetTransformInfo &TTI = LookupTTI(*ParentFunc);
+ expandMemCpyAsLoop(Memcpy, TTI);
+ Changed = true;
+ Memcpy->eraseFromParent();
+ break;
+ }
case Intrinsic::memmove: {
auto *Memmove = cast<MemMoveInst>(Inst);
Function *ParentFunc = Memmove->getFunction();
@@ -291,6 +306,7 @@ bool PreISelIntrinsicLowering::lowerIntrinsics(Module &M) const {
default:
break;
case Intrinsic::memcpy:
+ case Intrinsic::memcpy_inline:
case Intrinsic::memmove:
case Intrinsic::memset:
case Intrinsic::memset_inline:
diff --git a/llvm/test/Transforms/PreISelIntrinsicLowering/X86/memcpy-inline-non-constant-len.ll b/llvm/test/Transforms/PreISelIntrinsicLowering/X86/memcpy-inline-non-constant-len.ll
new file mode 100644
index 0000000000000..5fe1f55ec272b
--- /dev/null
+++ b/llvm/test/Transforms/PreISelIntrinsicLowering/X86/memcpy-inline-non-constant-len.ll
@@ -0,0 +1,34 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -mtriple=x86_64-pc-linux-gnu -passes=pre-isel-intrinsic-lowering -S -o - %s | FileCheck %s
+
+; Constant length memcpy.inline should be left unmodified.
+define void @memcpy_32(ptr %dst, ptr %src) nounwind {
+; CHECK-LABEL: define void @memcpy_32(
+; CHECK-SAME: ptr [[DST:%.*]], ptr [[SRC:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT: tail call void @llvm.memcpy.inline.p0.p0.i64(ptr [[DST]], ptr [[SRC]], i64 32, i1 false)
+; CHECK-NEXT: ret void
+;
+ tail call void @llvm.memcpy.inline.p0.p0.i64(ptr %dst, ptr %src, i64 32, i1 0)
+ ret void
+}
+
+define void @memcpy_x(ptr %dst, ptr %src, i64 %x) nounwind {
+; CHECK-LABEL: define void @memcpy_x(
+; CHECK-SAME: ptr [[DST:%.*]], ptr [[SRC:%.*]], i64 [[X:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT: [[TMP1:%.*]] = icmp ne i64 [[X]], 0
+; CHECK-NEXT: br i1 [[TMP1]], label %[[LOOP_MEMCPY_EXPANSION:.*]], label %[[POST_LOOP_MEMCPY_EXPANSION:.*]]
+; CHECK: [[LOOP_MEMCPY_EXPANSION]]:
+; CHECK-NEXT: [[LOOP_INDEX:%.*]] = phi i64 [ 0, [[TMP0:%.*]] ], [ [[TMP5:%.*]], %[[LOOP_MEMCPY_EXPANSION]] ]
+; CHECK-NEXT: [[TMP2:%.*]] = getelementptr inbounds i8, ptr [[SRC]], i64 [[LOOP_INDEX]]
+; CHECK-NEXT: [[TMP3:%.*]] = load i8, ptr [[TMP2]], align 1
+; CHECK-NEXT: [[TMP4:%.*]] = getelementptr inbounds i8, ptr [[DST]], i64 [[LOOP_INDEX]]
+; CHECK-NEXT: store i8 [[TMP3]], ptr [[TMP4]], align 1
+; CHECK-NEXT: [[TMP5]] = add i64 [[LOOP_INDEX]], 1
+; CHECK-NEXT: [[TMP6:%.*]] = icmp ult i64 [[TMP5]], [[X]]
+; CHECK-NEXT: br i1 [[TMP6]], label %[[LOOP_MEMCPY_EXPANSION]], label %[[POST_LOOP_MEMCPY_EXPANSION]]
+; CHECK: [[POST_LOOP_MEMCPY_EXPANSION]]:
+; CHECK-NEXT: ret void
+;
+ tail call void @llvm.memcpy.inline.p0.p0.i64(ptr %dst, ptr %src, i64 %x, i1 0)
+ ret void
+}
diff --git a/llvm/test/Verifier/intrinsic-immarg.ll b/llvm/test/Verifier/intrinsic-immarg.ll
index b1b9f7ee4be11..ad70b17e5fb72 100644
--- a/llvm/test/Verifier/intrinsic-immarg.ll
+++ b/llvm/test/Verifier/intrinsic-immarg.ll
@@ -36,14 +36,6 @@ define void @memcpy_inline_is_volatile(ptr %dest, ptr %src, i1 %is.volatile) {
ret void
}
-define void @memcpy_inline_variable_size(ptr %dest, ptr %src, i32 %size) {
- ; CHECK: immarg operand has non-immediate parameter
- ; CHECK-NEXT: i32 %size
- ; CHECK-NEXT: call void @llvm.memcpy.inline.p0.p0.i32(ptr %dest, ptr %src, i32 %size, i1 true)
- call void @llvm.memcpy.inline.p0.p0.i32(ptr %dest, ptr %src, i32 %size, i1 true)
- ret void
-}
-
declare void @llvm.memmove.p0.p0.i32(ptr nocapture, ptr nocapture, i32, i1)
define void @memmove(ptr %dest, ptr %src, i1 %is.volatile) {
; CHECK: immarg operand has non-immediate parameter
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