[llvm] [X86] Use AlwaysInline to determine whether to emit code or bail when inlining is determined to be unprofitable (PR #87003)
via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 5 10:34:51 PDT 2024
https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/87003
>From 652ee724602b4c5bd6f2ac4b182574ac8c7cca0b Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Thu, 28 Mar 2024 16:19:34 -0400
Subject: [PATCH] [X86] For minsize, use size for alignment, rather than actual
alignment.
If we have minsize, then don't care about the alignment.
On x86, the CPU doesn't care and neither should you.
As long as the count is aligned, we can use less instructions.
---
llvm/lib/Target/X86/X86SelectionDAGInfo.cpp | 108 +++++++++-----
.../CodeGen/X86/memset-vs-memset-inline.ll | 135 +-----------------
2 files changed, 77 insertions(+), 166 deletions(-)
diff --git a/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp b/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
index 7c630a2b0da080..7c9f83aebfeb44 100644
--- a/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
+++ b/llvm/lib/Target/X86/X86SelectionDAGInfo.cpp
@@ -67,10 +67,27 @@ SDValue X86SelectionDAGInfo::EmitTargetCodeForMemset(
// The libc version is likely to be faster for these cases. It can use the
// address value and run time information about the CPU.
if (Alignment < Align(4) || !ConstantSize ||
- ConstantSize->getZExtValue() > Subtarget.getMaxInlineSizeThreshold())
+ ConstantSize->getZExtValue() > Subtarget.getMaxInlineSizeThreshold())
return SDValue();
+ // If we have minsize, then don't care about the alignment.
+ // On x86, the CPU doesn't care and neither should you.
+ // As long as the count is aligned, we can use the minimum number of
+ // instructions without always having to resort to strosb.
+ //
+ // Because this is a feature specific to x86, we must handle it here.
uint64_t SizeVal = ConstantSize->getZExtValue();
+ if (DAG.getMachineFunction().getFunction().hasMinSize()) {
+ if ((SizeVal & 7) == 0 && Subtarget.is64Bit())
+ Alignment = Align(8);
+ else if ((SizeVal & 3) == 0)
+ Alignment = Align(4);
+ else if ((SizeVal & 1) == 0)
+ Alignment = Align(2);
+ else
+ Alignment = Align(1);
+ }
+
SDValue InGlue;
EVT AVT;
SDValue Count;
@@ -120,34 +137,37 @@ SDValue X86SelectionDAGInfo::EmitTargetCodeForMemset(
}
bool Use64BitRegs = Subtarget.isTarget64BitLP64();
- Chain = DAG.getCopyToReg(Chain, dl, Use64BitRegs ? X86::RCX : X86::ECX,
- Count, InGlue);
+ Chain = DAG.getCopyToReg(Chain, dl, Use64BitRegs ? X86::RCX : X86::ECX, Count,
+ InGlue);
InGlue = Chain.getValue(1);
- Chain = DAG.getCopyToReg(Chain, dl, Use64BitRegs ? X86::RDI : X86::EDI,
- Dst, InGlue);
+ Chain = DAG.getCopyToReg(Chain, dl, Use64BitRegs ? X86::RDI : X86::EDI, Dst,
+ InGlue);
InGlue = Chain.getValue(1);
SDVTList Tys = DAG.getVTList(MVT::Other, MVT::Glue);
- SDValue Ops[] = { Chain, DAG.getValueType(AVT), InGlue };
- Chain = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops);
-
- if (BytesLeft) {
- // Handle the last 1 - 7 bytes.
- unsigned Offset = SizeVal - BytesLeft;
- EVT AddrVT = Dst.getValueType();
- EVT SizeVT = Size.getValueType();
-
- Chain =
- DAG.getMemset(Chain, dl,
- DAG.getNode(ISD::ADD, dl, AddrVT, Dst,
- DAG.getConstant(Offset, dl, AddrVT)),
- Val, DAG.getConstant(BytesLeft, dl, SizeVT), Alignment,
- isVolatile, AlwaysInline,
- /* isTailCall */ false, DstPtrInfo.getWithOffset(Offset));
- }
+ SDValue Ops[] = {Chain, DAG.getValueType(AVT), InGlue};
+ SDValue RepStos = DAG.getNode(X86ISD::REP_STOS, dl, Tys, Ops);
+
+ /// RepStos can process the whole length.
+ if (BytesLeft == 0)
+ return RepStos;
- // TODO: Use a Tokenfactor, as in memcpy, instead of a single chain.
- return Chain;
+ // Handle the last 1 - 7 bytes.
+ SmallVector<SDValue, 4> Results;
+ Results.push_back(RepStos);
+ unsigned Offset = SizeVal - BytesLeft;
+ EVT AddrVT = Dst.getValueType();
+ EVT SizeVT = Size.getValueType();
+
+ Results.push_back(
+ DAG.getMemset(Chain, dl,
+ DAG.getNode(ISD::ADD, dl, AddrVT, Dst,
+ DAG.getConstant(Offset, dl, AddrVT)),
+ Val, DAG.getConstant(BytesLeft, dl, SizeVT), Alignment,
+ isVolatile, /* isAlwaysInline */ true,
+ /* isTailCall */ false, DstPtrInfo.getWithOffset(Offset)));
+
+ return DAG.getNode(ISD::TokenFactor, dl, MVT::Other, Results);
}
/// Emit a single REP MOVS{B,W,D,Q} instruction.
@@ -208,11 +228,6 @@ static SDValue emitConstantSizeRepmov(
Align Alignment, bool isVolatile, bool AlwaysInline,
MachinePointerInfo DstPtrInfo, MachinePointerInfo SrcPtrInfo) {
- /// TODO: Revisit next line: big copy with ERMSB on march >= haswell are very
- /// efficient.
- if (!AlwaysInline && Size > Subtarget.getMaxInlineSizeThreshold())
- return SDValue();
-
/// If we have enhanced repmovs we use it.
if (Subtarget.hasERMSB())
return emitRepmovsB(Subtarget, DAG, dl, Chain, Dst, Src, Size);
@@ -220,13 +235,41 @@ static SDValue emitConstantSizeRepmov(
assert(!Subtarget.hasERMSB() && "No efficient RepMovs");
/// We assume runtime memcpy will do a better job for unaligned copies when
/// ERMS is not present.
- if (!AlwaysInline && (Alignment.value() & 3) != 0)
+ if (!AlwaysInline &&
+ (Alignment < Align(4) || Size > Subtarget.getMaxInlineSizeThreshold()))
return SDValue();
+ // If we have minsize, then don't care about the alignment.
+ // On x86, the CPU doesn't care and neither should you.
+ // As long as the count is aligned, we can use the minimum number of
+ // instructions without always having to resort to movsb
+ //
+ // Because this is a feature specific to x86, we must handle it here.
+ if (DAG.getMachineFunction().getFunction().hasMinSize()) {
+ if ((Size & 7) == 0 && Subtarget.is64Bit())
+ Alignment = Align(8);
+ else if ((Size & 3) == 0)
+ Alignment = Align(4);
+ else if ((Size & 1) == 0)
+ Alignment = Align(2);
+ else
+ Alignment = Align(1);
+ }
+
const MVT BlockType = getOptimalRepmovsType(Subtarget, Alignment);
const uint64_t BlockBytes = BlockType.getSizeInBits() / 8;
const uint64_t BlockCount = Size / BlockBytes;
const uint64_t BytesLeft = Size % BlockBytes;
+
+ if (DAG.getMachineFunction().getFunction().hasMinSize()) {
+ // Use movsb even if it is slow; the less instructions the better.
+ if (BytesLeft)
+ return emitRepmovsB(Subtarget, DAG, dl, Chain, Dst, Src, Size);
+
+ return emitRepmovs(Subtarget, DAG, dl, Chain, Dst, Src,
+ DAG.getIntPtrConstant(BlockCount, dl), BlockType);
+ }
+
SDValue RepMovs =
emitRepmovs(Subtarget, DAG, dl, Chain, Dst, Src,
DAG.getIntPtrConstant(BlockCount, dl), BlockType);
@@ -237,11 +280,6 @@ static SDValue emitConstantSizeRepmov(
assert(BytesLeft && "We have leftover at this point");
- /// In case we optimize for size we use repmovsb even if it's less efficient
- /// so we can save the loads/stores of the leftover.
- if (DAG.getMachineFunction().getFunction().hasMinSize())
- return emitRepmovsB(Subtarget, DAG, dl, Chain, Dst, Src, Size);
-
// Handle the last 1 - 7 bytes.
SmallVector<SDValue, 4> Results;
Results.push_back(RepMovs);
diff --git a/llvm/test/CodeGen/X86/memset-vs-memset-inline.ll b/llvm/test/CodeGen/X86/memset-vs-memset-inline.ll
index b8fdd936b43895..16022c6cbb3934 100644
--- a/llvm/test/CodeGen/X86/memset-vs-memset-inline.ll
+++ b/llvm/test/CodeGen/X86/memset-vs-memset-inline.ll
@@ -28,137 +28,10 @@ define void @regular_memset_calls_external_function(ptr %a, i8 %value) nounwind
define void @inlined_set_doesnt_call_external_function(ptr %a, i8 %value) nounwind {
; CHECK-LABEL: inlined_set_doesnt_call_external_function:
; CHECK: # %bb.0:
-; CHECK-NEXT: movzbl %sil, %ecx
-; CHECK-NEXT: movabsq $72340172838076673, %rax # imm = 0x101010101010101
-; CHECK-NEXT: imulq %rcx, %rax
-; CHECK-NEXT: movq %rax, 1016(%rdi)
-; CHECK-NEXT: movq %rax, 1008(%rdi)
-; CHECK-NEXT: movq %rax, 1000(%rdi)
-; CHECK-NEXT: movq %rax, 992(%rdi)
-; CHECK-NEXT: movq %rax, 984(%rdi)
-; CHECK-NEXT: movq %rax, 976(%rdi)
-; CHECK-NEXT: movq %rax, 968(%rdi)
-; CHECK-NEXT: movq %rax, 960(%rdi)
-; CHECK-NEXT: movq %rax, 952(%rdi)
-; CHECK-NEXT: movq %rax, 944(%rdi)
-; CHECK-NEXT: movq %rax, 936(%rdi)
-; CHECK-NEXT: movq %rax, 928(%rdi)
-; CHECK-NEXT: movq %rax, 920(%rdi)
-; CHECK-NEXT: movq %rax, 912(%rdi)
-; CHECK-NEXT: movq %rax, 904(%rdi)
-; CHECK-NEXT: movq %rax, 896(%rdi)
-; CHECK-NEXT: movq %rax, 888(%rdi)
-; CHECK-NEXT: movq %rax, 880(%rdi)
-; CHECK-NEXT: movq %rax, 872(%rdi)
-; CHECK-NEXT: movq %rax, 864(%rdi)
-; CHECK-NEXT: movq %rax, 856(%rdi)
-; CHECK-NEXT: movq %rax, 848(%rdi)
-; CHECK-NEXT: movq %rax, 840(%rdi)
-; CHECK-NEXT: movq %rax, 832(%rdi)
-; CHECK-NEXT: movq %rax, 824(%rdi)
-; CHECK-NEXT: movq %rax, 816(%rdi)
-; CHECK-NEXT: movq %rax, 808(%rdi)
-; CHECK-NEXT: movq %rax, 800(%rdi)
-; CHECK-NEXT: movq %rax, 792(%rdi)
-; CHECK-NEXT: movq %rax, 784(%rdi)
-; CHECK-NEXT: movq %rax, 776(%rdi)
-; CHECK-NEXT: movq %rax, 768(%rdi)
-; CHECK-NEXT: movq %rax, 760(%rdi)
-; CHECK-NEXT: movq %rax, 752(%rdi)
-; CHECK-NEXT: movq %rax, 744(%rdi)
-; CHECK-NEXT: movq %rax, 736(%rdi)
-; CHECK-NEXT: movq %rax, 728(%rdi)
-; CHECK-NEXT: movq %rax, 720(%rdi)
-; CHECK-NEXT: movq %rax, 712(%rdi)
-; CHECK-NEXT: movq %rax, 704(%rdi)
-; CHECK-NEXT: movq %rax, 696(%rdi)
-; CHECK-NEXT: movq %rax, 688(%rdi)
-; CHECK-NEXT: movq %rax, 680(%rdi)
-; CHECK-NEXT: movq %rax, 672(%rdi)
-; CHECK-NEXT: movq %rax, 664(%rdi)
-; CHECK-NEXT: movq %rax, 656(%rdi)
-; CHECK-NEXT: movq %rax, 648(%rdi)
-; CHECK-NEXT: movq %rax, 640(%rdi)
-; CHECK-NEXT: movq %rax, 632(%rdi)
-; CHECK-NEXT: movq %rax, 624(%rdi)
-; CHECK-NEXT: movq %rax, 616(%rdi)
-; CHECK-NEXT: movq %rax, 608(%rdi)
-; CHECK-NEXT: movq %rax, 600(%rdi)
-; CHECK-NEXT: movq %rax, 592(%rdi)
-; CHECK-NEXT: movq %rax, 584(%rdi)
-; CHECK-NEXT: movq %rax, 576(%rdi)
-; CHECK-NEXT: movq %rax, 568(%rdi)
-; CHECK-NEXT: movq %rax, 560(%rdi)
-; CHECK-NEXT: movq %rax, 552(%rdi)
-; CHECK-NEXT: movq %rax, 544(%rdi)
-; CHECK-NEXT: movq %rax, 536(%rdi)
-; CHECK-NEXT: movq %rax, 528(%rdi)
-; CHECK-NEXT: movq %rax, 520(%rdi)
-; CHECK-NEXT: movq %rax, 512(%rdi)
-; CHECK-NEXT: movq %rax, 504(%rdi)
-; CHECK-NEXT: movq %rax, 496(%rdi)
-; CHECK-NEXT: movq %rax, 488(%rdi)
-; CHECK-NEXT: movq %rax, 480(%rdi)
-; CHECK-NEXT: movq %rax, 472(%rdi)
-; CHECK-NEXT: movq %rax, 464(%rdi)
-; CHECK-NEXT: movq %rax, 456(%rdi)
-; CHECK-NEXT: movq %rax, 448(%rdi)
-; CHECK-NEXT: movq %rax, 440(%rdi)
-; CHECK-NEXT: movq %rax, 432(%rdi)
-; CHECK-NEXT: movq %rax, 424(%rdi)
-; CHECK-NEXT: movq %rax, 416(%rdi)
-; CHECK-NEXT: movq %rax, 408(%rdi)
-; CHECK-NEXT: movq %rax, 400(%rdi)
-; CHECK-NEXT: movq %rax, 392(%rdi)
-; CHECK-NEXT: movq %rax, 384(%rdi)
-; CHECK-NEXT: movq %rax, 376(%rdi)
-; CHECK-NEXT: movq %rax, 368(%rdi)
-; CHECK-NEXT: movq %rax, 360(%rdi)
-; CHECK-NEXT: movq %rax, 352(%rdi)
-; CHECK-NEXT: movq %rax, 344(%rdi)
-; CHECK-NEXT: movq %rax, 336(%rdi)
-; CHECK-NEXT: movq %rax, 328(%rdi)
-; CHECK-NEXT: movq %rax, 320(%rdi)
-; CHECK-NEXT: movq %rax, 312(%rdi)
-; CHECK-NEXT: movq %rax, 304(%rdi)
-; CHECK-NEXT: movq %rax, 296(%rdi)
-; CHECK-NEXT: movq %rax, 288(%rdi)
-; CHECK-NEXT: movq %rax, 280(%rdi)
-; CHECK-NEXT: movq %rax, 272(%rdi)
-; CHECK-NEXT: movq %rax, 264(%rdi)
-; CHECK-NEXT: movq %rax, 256(%rdi)
-; CHECK-NEXT: movq %rax, 248(%rdi)
-; CHECK-NEXT: movq %rax, 240(%rdi)
-; CHECK-NEXT: movq %rax, 232(%rdi)
-; CHECK-NEXT: movq %rax, 224(%rdi)
-; CHECK-NEXT: movq %rax, 216(%rdi)
-; CHECK-NEXT: movq %rax, 208(%rdi)
-; CHECK-NEXT: movq %rax, 200(%rdi)
-; CHECK-NEXT: movq %rax, 192(%rdi)
-; CHECK-NEXT: movq %rax, 184(%rdi)
-; CHECK-NEXT: movq %rax, 176(%rdi)
-; CHECK-NEXT: movq %rax, 168(%rdi)
-; CHECK-NEXT: movq %rax, 160(%rdi)
-; CHECK-NEXT: movq %rax, 152(%rdi)
-; CHECK-NEXT: movq %rax, 144(%rdi)
-; CHECK-NEXT: movq %rax, 136(%rdi)
-; CHECK-NEXT: movq %rax, 128(%rdi)
-; CHECK-NEXT: movq %rax, 120(%rdi)
-; CHECK-NEXT: movq %rax, 112(%rdi)
-; CHECK-NEXT: movq %rax, 104(%rdi)
-; CHECK-NEXT: movq %rax, 96(%rdi)
-; CHECK-NEXT: movq %rax, 88(%rdi)
-; CHECK-NEXT: movq %rax, 80(%rdi)
-; CHECK-NEXT: movq %rax, 72(%rdi)
-; CHECK-NEXT: movq %rax, 64(%rdi)
-; CHECK-NEXT: movq %rax, 56(%rdi)
-; CHECK-NEXT: movq %rax, 48(%rdi)
-; CHECK-NEXT: movq %rax, 40(%rdi)
-; CHECK-NEXT: movq %rax, 32(%rdi)
-; CHECK-NEXT: movq %rax, 24(%rdi)
-; CHECK-NEXT: movq %rax, 16(%rdi)
-; CHECK-NEXT: movq %rax, 8(%rdi)
-; CHECK-NEXT: movq %rax, (%rdi)
+; CHECK-NEXT: movl %esi, %eax
+; CHECK-NEXT: movl $1024, %ecx # imm = 0x400
+; CHECK-NEXT: # kill: def $al killed $al killed $eax
+; CHECK-NEXT: rep;stosb %al, %es:(%rdi)
; CHECK-NEXT: retq
tail call void @llvm.memset.inline.p0.i64(ptr %a, i8 %value, i64 1024, i1 0)
ret void
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