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[GlobalMerge] Set the alignment on merged global structs 

If no alignment is set, the abi/preferred alignment of structs will be
used which may be higher than required. This can lead to extra padding
and in the end an increase in data size.

Differential Revision: https://reviews.llvm.org/D47633

llvm-svn: 334099
This commit is contained in:
David Green 2018-06-06 14:48:32 +00:00
parent 566c74cc98
commit 25312b2b6c
11 changed files with 45 additions and 16 deletions
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5
llvm/lib/CodeGen/GlobalMerge.cpp
View File

@ -500,6 +500,11 @@ bool GlobalMerge::doMerge(const SmallVectorImpl<GlobalVariable *> &Globals,
GlobalVariable::NotThreadLocal, AddrSpace);
const StructLayout *MergedLayout = DL.getStructLayout(MergedTy);
// Set the alignment of the merged struct as the maximum alignment of the
// globals to prevent over-alignment. We don't handle globals that are not
// default aligned, so the alignment of the MergedLayout struct is
// equivalent.
MergedGV->setAlignment(MergedLayout->getAlignment());
for (ssize_t k = i, idx = 0; k != j; k = GlobalSet.find_next(k), ++idx) {
GlobalValue::LinkageTypes Linkage = Globals[k]->getLinkage();

4
llvm/test/CodeGen/AArch64/global-merge-1.ll
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@ -22,10 +22,10 @@ define void @f1(i32 %a1, i32 %a2) {
;CHECK: .type .L_MergedGlobals,@object // @_MergedGlobals
;CHECK: .local .L_MergedGlobals
;CHECK: .comm .L_MergedGlobals,8,8
;CHECK: .comm .L_MergedGlobals,8,4
;CHECK: .set m, .L_MergedGlobals
;CHECK: .set n, .L_MergedGlobals+4
;CHECK-APPLE-IOS: .zerofill __DATA,__bss,__MergedGlobals,8,3 ; @_MergedGlobals
;CHECK-APPLE-IOS: .zerofill __DATA,__bss,__MergedGlobals,8,2 ; @_MergedGlobals
;CHECK-APPLE-IOS-NOT: .set _m, l__MergedGlobals
;CHECK-APPLE-IOS-NOT: .set _n, l__MergedGlobals+4

4
llvm/test/CodeGen/AArch64/global-merge-2.ll
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@ -29,7 +29,7 @@ define void @g1(i32 %a1, i32 %a2) {
;CHECK: .type .L_MergedGlobals,@object // @_MergedGlobals
;CHECK: .local .L_MergedGlobals
;CHECK: .comm .L_MergedGlobals,12,8
;CHECK: .comm .L_MergedGlobals,12,4
;CHECK: .globl x
;CHECK: .set x, .L_MergedGlobals
@ -41,7 +41,7 @@ define void @g1(i32 %a1, i32 %a2) {
;CHECK: .set z, .L_MergedGlobals+8
;CHECK: .size z, 4
;CHECK-APPLE-IOS: .zerofill __DATA,__common,__MergedGlobals_x,12,3
;CHECK-APPLE-IOS: .zerofill __DATA,__common,__MergedGlobals_x,12,2
;CHECK-APPLE-IOS: .globl _x
;CHECK-APPLE-IOS: .set {{.*}}, __MergedGlobals_x

4
llvm/test/CodeGen/AArch64/global-merge-3.ll
View File

@ -21,13 +21,13 @@ define void @f1(i32 %a1, i32 %a2, i32 %a3) {
}
;CHECK: .type .L_MergedGlobals,@object // @_MergedGlobals
;CHECK: .p2align 4
;CHECK: .p2align 2
;CHECK: .L_MergedGlobals:
;CHECK: .size .L_MergedGlobals, 4004
;CHECK-APPLE-IOS: .zerofill __DATA,__common,_y,4000,2
;CHECK-APPLE-IOS: .p2align 4
;CHECK-APPLE-IOS: .p2align 2
;CHECK-APPLE-IOS: __MergedGlobals_x:
;CHECK-APPLE-IOS: .long 1
;CHECK-APPLE-IOS: .space 4000

2
llvm/test/CodeGen/AArch64/global-merge-4.ll
View File

@ -66,7 +66,7 @@ define internal i32* @returnFoo() #1 {
;CHECK: .type .L_MergedGlobals,@object // @_MergedGlobals
;CHECK: .local .L_MergedGlobals
;CHECK: .comm .L_MergedGlobals,60,16
;CHECK: .comm .L_MergedGlobals,60,4
attributes #0 = { nounwind ssp }
attributes #1 = { nounwind readnone ssp }

6
llvm/test/CodeGen/AArch64/global-merge-group-by-use.ll
View File

@ -88,8 +88,8 @@ define void @f5(i32 %a1) #0 {
; CHECK-DAG: .zerofill __DATA,__bss,_o5,4,2
; CHECK-DAG: .zerofill __DATA,__bss,[[SET1]],8,3
; CHECK-DAG: .zerofill __DATA,__bss,[[SET2]],12,3
; CHECK-DAG: .zerofill __DATA,__bss,[[SET3]],12,3
; CHECK-DAG: .zerofill __DATA,__bss,[[SET1]],8,2
; CHECK-DAG: .zerofill __DATA,__bss,[[SET2]],12,2
; CHECK-DAG: .zerofill __DATA,__bss,[[SET3]],12,2
attributes #0 = { nounwind }

2
llvm/test/CodeGen/AArch64/global-merge-ignore-single-use-minsize.ll
View File

@ -67,7 +67,7 @@ define void @f4(i32 %a1, i32 %a2) nounwind {
ret void
}
; CHECK-DAG: .zerofill __DATA,__bss,[[SET]],16,3
; CHECK-DAG: .zerofill __DATA,__bss,[[SET]],16,2
; CHECK-DAG: .zerofill __DATA,__bss,_m2,4,2
; CHECK-DAG: .zerofill __DATA,__bss,_n2,4,2
; CHECK-DAG: .zerofill __DATA,__bss,_n4,4,2

2
llvm/test/CodeGen/AArch64/global-merge-ignore-single-use.ll
View File

@ -58,7 +58,7 @@ define void @f4(i32 %a1) #0 {
ret void
}
; CHECK-DAG: .zerofill __DATA,__bss,[[SET]],20,4
; CHECK-DAG: .zerofill __DATA,__bss,[[SET]],20,2
; CHECK-DAG: .zerofill __DATA,__bss,_o2,4,2
attributes #0 = { nounwind }

6
llvm/test/CodeGen/ARM/global-merge-1.ll
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@ -11,16 +11,16 @@
; MERGE-NOT: .zerofill __DATA,__bss,_bar,20,2
; MERGE-NOT: .zerofill __DATA,__bss,_baz,20,2
; MERGE-NOT: .zerofill __DATA,__bss,_foo,20,2
; MERGE: .zerofill __DATA,__bss,__MergedGlobals,60,4
; MERGE: .zerofill __DATA,__bss,__MergedGlobals,60,2
; MERGE-NOT: .zerofill __DATA,__bss,_bar,20,2
; MERGE-NOT: .zerofill __DATA,__bss,_baz,20,2
; MERGE-NOT: .zerofill __DATA,__bss,_foo,20,2
; NO-MERGE-NOT: .zerofill __DATA,__bss,__MergedGlobals,60,4
; NO-MERGE-NOT: .zerofill __DATA,__bss,__MergedGlobals,60,2
; NO-MERGE: .zerofill __DATA,__bss,_bar,20,2
; NO-MERGE: .zerofill __DATA,__bss,_baz,20,2
; NO-MERGE: .zerofill __DATA,__bss,_foo,20,2
; NO-MERGE-NOT: .zerofill __DATA,__bss,__MergedGlobals,60,4
; NO-MERGE-NOT: .zerofill __DATA,__bss,__MergedGlobals,60,2
target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:32:64-v128:32:128-a0:0:32-n32-S32"
target triple = "thumbv7-apple-ios3.0.0"

24
llvm/test/CodeGen/ARM/global-merge-alignment.ll Normal file
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@ -0,0 +1,24 @@
; RUN: llc < %s -arm-global-merge -data-sections | FileCheck %s
target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
target triple = "thumbv7em-arm-none-eabi"
@f = local_unnamed_addr global [4 x i32*] zeroinitializer, align 4
@d = local_unnamed_addr global i64 0, align 8
;CHECK: .section .bss..L_MergedGlobals,"aw",%nobits
;CHECK-NEXT: .p2align 3
;CHECK-NEXT: .L_MergedGlobals:
;CHECK-NEXT: .zero 24
;CHECK-NEXT: .size .L_MergedGlobals, 24
define i32 @func_1() {
%1 = load i64, i64* @d, align 8
%2 = load i32*, i32** getelementptr inbounds ([4 x i32*], [4 x i32*]* @f, i32 0, i32 0), align 4
%3 = load i32, i32* %2, align 4
%4 = trunc i64 %1 to i32
%5 = add i32 %3, %4
ret i32 %5
}

2
llvm/test/Transforms/GlobalMerge/debug-info.ll
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@ -3,7 +3,7 @@
source_filename = "test/Transforms/GlobalMerge/debug-info.ll"
target datalayout = "e-p:64:64"
target triple = "x86_64-unknown-linux-gnu"
; CHECK: @_MergedGlobals = private global { i32, i32 } { i32 1, i32 2 }, !dbg [[A:![0-9]+]], !dbg [[B:![0-9]+]]
; CHECK: @_MergedGlobals = private global { i32, i32 } { i32 1, i32 2 }, align 4, !dbg [[A:![0-9]+]], !dbg [[B:![0-9]+]]
@a = internal global i32 1, !dbg !0
@b = internal global i32 2, !dbg !2