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[GlobalMerge] Add MinSize feature to the GlobalMerge Pass. #93686

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Jun 3, 2024
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[GlobalMerge] Add MinSize feature to the GlobalMerge Pass. #93686

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2 changes: 2 additions & 0 deletions llvm/include/llvm/CodeGen/GlobalMerge.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,8 @@ struct GlobalMergeOptions {
// functions), see the code that passes in the offset in the ARM backend
// for more information.
unsigned MaxOffset = 0;
// The minimum size in bytes of each global that should considered in merging.
unsigned MinSize = 0;
bool GroupByUse = true;
bool IgnoreSingleUse = true;
bool MergeConst = false;
Expand Down
22 changes: 21 additions & 1 deletion llvm/lib/CodeGen/GlobalMerge.cpp
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Expand Up @@ -134,6 +134,12 @@ static cl::opt<cl::boolOrDefault>
EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden,
cl::desc("Enable global merge pass on external linkage"));

static cl::opt<unsigned>
GlobalMergeMinDataSize("global-merge-min-data-size",
cl::desc("The minimum size in bytes of each global "
"that should considered in merging."),
cl::init(0), cl::Hidden);

STATISTIC(NumMerged, "Number of globals merged");

namespace {
Expand Down Expand Up @@ -198,6 +204,19 @@ class GlobalMerge : public FunctionPass {
}

bool doInitialization(Module &M) override {
auto GetSmallDataLimit = [](Module &M) -> std::optional<uint64_t> {
Metadata *SDL = M.getModuleFlag("SmallDataLimit");
if (!SDL)
return std::nullopt;
return mdconst::extract<ConstantInt>(SDL)->getZExtValue();
};
if (GlobalMergeMinDataSize.getNumOccurrences())
Opt.MinSize = GlobalMergeMinDataSize;
else if (auto SDL = GetSmallDataLimit(M); SDL && *SDL > 0)
Opt.MinSize = *SDL + 1;
else
Opt.MinSize = 0;

GlobalMergeImpl P(TM, Opt);
return P.run(M);
}
Expand Down Expand Up @@ -670,7 +689,8 @@ bool GlobalMergeImpl::run(Module &M) {
continue;

Type *Ty = GV.getValueType();
if (DL.getTypeAllocSize(Ty) < Opt.MaxOffset) {
TypeSize AllocSize = DL.getTypeAllocSize(Ty);
if (AllocSize < Opt.MaxOffset && AllocSize >= Opt.MinSize) {
if (TM &&
TargetLoweringObjectFile::getKindForGlobal(&GV, *TM).isBSS())
BSSGlobals[{AddressSpace, Section}].push_back(&GV);
Expand Down
48 changes: 48 additions & 0 deletions llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-nonzero.ll
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@@ -0,0 +1,48 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -verify-machineinstrs < %s \
; RUN: | FileCheck %s -check-prefix=SMALL-DATA
; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -global-merge-min-data-size=0 \
; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=MINSIZE

@ig1 = internal global i32 0, align 4
@ig2 = internal global i32 0, align 4

@eg1 = dso_local global i32 0, align 4
@eg2 = dso_local global i32 0, align 4

; This test shows that GlobalDataMinSize is set to SmallDataLimit + 1 when
; SmallDataLimit module flag is set as non-zero, and that global-merge-min-data-size
; overrides the small data limit.

define void @f1(i32 %a) nounwind {
; SMALL-DATA-LABEL: f1:
; SMALL-DATA: # %bb.0:
; SMALL-DATA-NEXT: lui a1, %hi(ig1)
; SMALL-DATA-NEXT: sw a0, %lo(ig1)(a1)
; SMALL-DATA-NEXT: lui a1, %hi(ig2)
; SMALL-DATA-NEXT: sw a0, %lo(ig2)(a1)
; SMALL-DATA-NEXT: lui a1, %hi(eg1)
; SMALL-DATA-NEXT: sw a0, %lo(eg1)(a1)
; SMALL-DATA-NEXT: lui a1, %hi(eg2)
; SMALL-DATA-NEXT: sw a0, %lo(eg2)(a1)
; SMALL-DATA-NEXT: ret
;
; MINSIZE-LABEL: f1:
; MINSIZE: # %bb.0:
; MINSIZE-NEXT: lui a1, %hi(.L_MergedGlobals)
; MINSIZE-NEXT: sw a0, %lo(.L_MergedGlobals)(a1)
; MINSIZE-NEXT: addi a1, a1, %lo(.L_MergedGlobals)
; MINSIZE-NEXT: sw a0, 4(a1)
; MINSIZE-NEXT: sw a0, 8(a1)
; MINSIZE-NEXT: sw a0, 12(a1)
; MINSIZE-NEXT: ret
store i32 %a, ptr @ig1, align 4
store i32 %a, ptr @ig2, align 4
store i32 %a, ptr @eg1, align 4
store i32 %a, ptr @eg2, align 4
ret void
}


!llvm.module.flags = !{!0}
!0 = !{i32 8, !"SmallDataLimit", i32 8}
49 changes: 49 additions & 0 deletions llvm/test/CodeGen/RISCV/global-merge-minsize-smalldata-zero.ll
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@@ -0,0 +1,49 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -verify-machineinstrs < %s \
; RUN: | FileCheck %s -check-prefix=SMALL-DATA
; RUN: llc -mtriple=riscv64 -riscv-enable-global-merge -global-merge-min-data-size=5 \
; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=MINSIZE

@ig1 = internal global i32 0, align 4
@ig2 = internal global i32 0, align 4

@eg1 = dso_local global i32 0, align 4
@eg2 = dso_local global i32 0, align 4


; This test shows that GlobalDataMinSize is set to 0 when SmallDataLimit module
; flag is set to zero, and that the global-merge-min-data-size option overrides
; the small data limit.

define void @f1(i32 %a) nounwind {
; SMALL-DATA-LABEL: f1:
; SMALL-DATA: # %bb.0:
; SMALL-DATA-NEXT: lui a1, %hi(.L_MergedGlobals)
; SMALL-DATA-NEXT: sw a0, %lo(.L_MergedGlobals)(a1)
; SMALL-DATA-NEXT: addi a1, a1, %lo(.L_MergedGlobals)
; SMALL-DATA-NEXT: sw a0, 4(a1)
; SMALL-DATA-NEXT: sw a0, 8(a1)
; SMALL-DATA-NEXT: sw a0, 12(a1)
; SMALL-DATA-NEXT: ret
;
; MINSIZE-LABEL: f1:
; MINSIZE: # %bb.0:
; MINSIZE-NEXT: lui a1, %hi(ig1)
; MINSIZE-NEXT: sw a0, %lo(ig1)(a1)
; MINSIZE-NEXT: lui a1, %hi(ig2)
; MINSIZE-NEXT: sw a0, %lo(ig2)(a1)
; MINSIZE-NEXT: lui a1, %hi(eg1)
; MINSIZE-NEXT: sw a0, %lo(eg1)(a1)
; MINSIZE-NEXT: lui a1, %hi(eg2)
; MINSIZE-NEXT: sw a0, %lo(eg2)(a1)
; MINSIZE-NEXT: ret
store i32 %a, ptr @ig1, align 4
store i32 %a, ptr @ig2, align 4
store i32 %a, ptr @eg1, align 4
store i32 %a, ptr @eg2, align 4
ret void
}


!llvm.module.flags = !{!0}
!0 = !{i32 8, !"SmallDataLimit", i32 0}
40 changes: 40 additions & 0 deletions llvm/test/CodeGen/RISCV/global-merge-minsize.ll
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@@ -0,0 +1,40 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -verify-machineinstrs < %s \
; RUN: | FileCheck %s -check-prefix=RV32
; RUN: llc -mtriple=riscv32 -riscv-enable-global-merge -global-merge-min-data-size=5 \
; RUN: -verify-machineinstrs < %s | FileCheck %s -check-prefix=RV32-MINSIZE

@ig1 = internal global i32 0, align 4
@ig2 = internal global i32 0, align 4

@eg1 = dso_local global i32 0, align 4
@eg2 = dso_local global i32 0, align 4

define void @f1(i32 %a) nounwind {
; RV32-LABEL: f1:
; RV32: # %bb.0:
; RV32-NEXT: lui a1, %hi(.L_MergedGlobals)
; RV32-NEXT: sw a0, %lo(.L_MergedGlobals)(a1)
; RV32-NEXT: addi a1, a1, %lo(.L_MergedGlobals)
; RV32-NEXT: sw a0, 4(a1)
; RV32-NEXT: sw a0, 8(a1)
; RV32-NEXT: sw a0, 12(a1)
; RV32-NEXT: ret
;
; RV32-MINSIZE-LABEL: f1:
; RV32-MINSIZE: # %bb.0:
; RV32-MINSIZE-NEXT: lui a1, %hi(ig1)
; RV32-MINSIZE-NEXT: sw a0, %lo(ig1)(a1)
; RV32-MINSIZE-NEXT: lui a1, %hi(ig2)
; RV32-MINSIZE-NEXT: sw a0, %lo(ig2)(a1)
; RV32-MINSIZE-NEXT: lui a1, %hi(eg1)
; RV32-MINSIZE-NEXT: sw a0, %lo(eg1)(a1)
; RV32-MINSIZE-NEXT: lui a1, %hi(eg2)
; RV32-MINSIZE-NEXT: sw a0, %lo(eg2)(a1)
; RV32-MINSIZE-NEXT: ret
store i32 %a, ptr @ig1, align 4
store i32 %a, ptr @ig2, align 4
store i32 %a, ptr @eg1, align 4
store i32 %a, ptr @eg2, align 4
ret void
}
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