[lld] r332169 - COFF: ICF a section and its associated sections as a unit.
Peter Collingbourne via llvm-commits
llvm-commits at lists.llvm.org
Fri May 11 19:12:41 PDT 2018
Author: pcc
Date: Fri May 11 19:12:40 2018
New Revision: 332169
URL: http://llvm.org/viewvc/llvm-project?rev=332169&view=rev
Log:
COFF: ICF a section and its associated sections as a unit.
This is needed to avoid merging two functions with identical
instructions but different xdata. It also reduces binary size by
deduplicating identical pdata sections.
Fixes PR35337.
Differential Revision: https://reviews.llvm.org/D46672
Added:
lld/trunk/test/COFF/icf-pdata.s
Modified:
lld/trunk/COFF/ICF.cpp
Modified: lld/trunk/COFF/ICF.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/ICF.cpp?rev=332169&r1=332168&r2=332169&view=diff
==============================================================================
--- lld/trunk/COFF/ICF.cpp (original)
+++ lld/trunk/COFF/ICF.cpp Fri May 11 19:12:40 2018
@@ -45,6 +45,8 @@ public:
private:
void segregate(size_t Begin, size_t End, bool Constant);
+ bool assocEquals(const SectionChunk *A, const SectionChunk *B);
+
bool equalsConstant(const SectionChunk *A, const SectionChunk *B);
bool equalsVariable(const SectionChunk *A, const SectionChunk *B);
@@ -91,8 +93,9 @@ bool ICF::isEligible(SectionChunk *C) {
if (C->getOutputCharacteristics() & llvm::COFF::IMAGE_SCN_MEM_EXECUTE)
return true;
- // .xdata unwind info sections are eligible.
- if (C->getSectionName().split('$').first == ".xdata")
+ // .pdata and .xdata unwind info sections are eligible.
+ StringRef OutSecName = C->getSectionName().split('$').first;
+ if (OutSecName == ".pdata" || OutSecName == ".xdata")
return true;
// So are vtables.
@@ -125,6 +128,19 @@ void ICF::segregate(size_t Begin, size_t
}
}
+// Returns true if two sections' associative children are equal.
+bool ICF::assocEquals(const SectionChunk *A, const SectionChunk *B) {
+ auto ChildClasses = [&](const SectionChunk *SC) {
+ std::vector<uint32_t> Classes;
+ for (const SectionChunk *C : SC->children())
+ if (!C->SectionName.startswith(".debug") &&
+ C->SectionName != ".gfids$y" && C->SectionName != ".gljmp$y")
+ Classes.push_back(C->Class[Cnt % 2]);
+ return Classes;
+ };
+ return ChildClasses(A) == ChildClasses(B);
+}
+
// Compare "non-moving" part of two sections, namely everything
// except relocation targets.
bool ICF::equalsConstant(const SectionChunk *A, const SectionChunk *B) {
@@ -154,7 +170,8 @@ bool ICF::equalsConstant(const SectionCh
return A->getOutputCharacteristics() == B->getOutputCharacteristics() &&
A->SectionName == B->SectionName && A->Alignment == B->Alignment &&
A->Header->SizeOfRawData == B->Header->SizeOfRawData &&
- A->Checksum == B->Checksum && A->getContents() == B->getContents();
+ A->Checksum == B->Checksum && A->getContents() == B->getContents() &&
+ assocEquals(A, B);
}
// Compare "moving" part of two sections, namely relocation targets.
@@ -170,7 +187,9 @@ bool ICF::equalsVariable(const SectionCh
return D1->getChunk()->Class[Cnt % 2] == D2->getChunk()->Class[Cnt % 2];
return false;
};
- return std::equal(A->Relocs.begin(), A->Relocs.end(), B->Relocs.begin(), Eq);
+ return std::equal(A->Relocs.begin(), A->Relocs.end(), B->Relocs.begin(),
+ Eq) &&
+ assocEquals(A, B);
}
// Find the first Chunk after Begin that has a different class from Begin.
Added: lld/trunk/test/COFF/icf-pdata.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/COFF/icf-pdata.s?rev=332169&view=auto
==============================================================================
--- lld/trunk/test/COFF/icf-pdata.s (added)
+++ lld/trunk/test/COFF/icf-pdata.s Fri May 11 19:12:40 2018
@@ -0,0 +1,97 @@
+# RUN: llvm-mc %s -triple x86_64-windows-msvc -filetype=obj -o %t.obj
+# RUN: lld-link %t.obj -dll -noentry -out:%t.dll -merge:.xdata=.xdata
+# RUN: llvm-readobj -sections -coff-exports %t.dll | FileCheck %s
+
+# CHECK: Name: .pdata
+# CHECK-NEXT: VirtualSize: 0x18
+# CHECK: Name: .xdata
+# CHECK-NEXT: VirtualSize: 0x10
+
+# CHECK: Name: xdata1
+# CHECK-NEXT: RVA: 0x1010
+# CHECK: Name: xdata1a
+# CHECK-NEXT: RVA: 0x1010
+# CHECK: Name: xdata1b
+# CHECK-NEXT: RVA: 0x1030
+
+ .text
+callee:
+ ret
+
+ .def xdata1;
+ .scl 2;
+ .type 32;
+ .endef
+ .section .text,"xr",one_only,xdata1
+ .globl xdata1 # -- Begin function xdata1
+ .p2align 4, 0x90
+xdata1: # @xdata1
+.seh_proc xdata1
+# BB#0: # %entry
+ subq $40, %rsp
+ .seh_stackalloc 40
+ .seh_endprologue
+ callq callee
+ nop
+ addq $40, %rsp
+ jmp callee # TAILCALL
+ .seh_handlerdata
+ .section .text,"xr",one_only,xdata1
+ .seh_endproc
+ # -- End function
+
+# xdata1a is identical to xdata1, so it should be ICFd, and so should its pdata.
+# It also has associative debug and CFG sections which should be ignored by ICF.
+ .def xdata1a;
+ .scl 2;
+ .type 32;
+ .endef
+ .section .text,"xr",one_only,xdata1a
+ .globl xdata1a # -- Begin function xdata1a
+ .p2align 4, 0x90
+xdata1a: # @xdata1a
+.seh_proc xdata1a
+# BB#0: # %entry
+ subq $40, %rsp
+ .seh_stackalloc 40
+ .seh_endprologue
+ callq callee
+ nop
+ addq $40, %rsp
+ jmp callee # TAILCALL
+ .seh_handlerdata
+ .section .text,"xr",one_only,xdata1a
+ .seh_endproc
+
+ .section .debug$S,"r",associative,xdata1a
+ .section .gfids$y,"r",associative,xdata1a
+ .section .gljmp$y,"r",associative,xdata1a
+
+# xdata1b's text is identical to xdata1, but its xdata specifies a different
+# stack size, so it cannot be ICFd with xdata1.
+ .def xdata1b;
+ .scl 2;
+ .type 32;
+ .endef
+ .section .text,"xr",one_only,xdata1b
+ .globl xdata1b # -- Begin function xdata1b
+ .p2align 4, 0x90
+xdata1b: # @xdata1b
+.seh_proc xdata1b
+# BB#0: # %entry
+ subq $40, %rsp
+ .seh_stackalloc 48
+ .seh_endprologue
+ callq callee
+ nop
+ addq $40, %rsp
+ jmp callee # TAILCALL
+ .seh_handlerdata
+ .section .text,"xr",one_only,xdata1b
+ .seh_endproc
+ # -- End function
+
+ .section .drectve,"yn"
+ .ascii " -export:xdata1"
+ .ascii " -export:xdata1a"
+ .ascii " -export:xdata1b"
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