[lld-macho] add tests for ICF, plus cleanups

[gkm]

Summary

Add tests for pending TODOs, plus some global cleanups:

• No fold: func has personality/LSDA
• Fold: reference to absolute symbol with different name but identical value
• No fold: reloc references to absolute symbols with different values
• No fold: N_ALT_ENTRY symbols

[int3]

Nice! Just one request: could we fix and test this too? https://reviews.llvm.org/D103292#inline-992625

lld/test/MachO/icf.s

6

-pie shouldn't be necessary, %lld expands out to include a modern platform_version that implies PIE

107

[gkm]

• revise according to review feedback

[int3]

Nice! Just one request: could we fix and test this too? https://reviews.llvm.org/D103292#inline-992625

As discussed offline, there seem to be underlying issues that make testing this hard, so we'll punt on it for now

lld/MachO/UnwindInfoSection.cpp

static void addEntriesForFunctionsWithoutUnwindInfo(
   DenseSet<Ptr> hasUnwindInfo;
   for (CompactUnwindEntry<Ptr> &cuEntry : cuVector)
     if (cuEntry.functionAddress != UINT64_MAX)
       hasUnwindInfo.insert(cuEntry.functionAddress);
 
   // Add explicit "has no unwind info" entries for all global and local symbols
   // without unwind info.
   auto markNoUnwindInfo = [&cuVector, &hasUnwindInfo](const Defined *d) {
-    if (d->isLive() && isCodeSection(d->isec)) {
+    if (d->isLive() && d->isec && isCodeSection(d->isec)) {
       Ptr ptr = d->getVA();
       if (!hasUnwindInfo.count(ptr))
         cuVector.push_back({ptr, 0, 0, 0, 0});
     }
   };
   for (Symbol *sym : symtab->getSymbols())
     if (auto *d = dyn_cast<Defined>(sym))
       markNoUnwindInfo(d);

lld/test/MachO/icf.s

 # REQUIRES: x86
-# RUN: rm -rf %t; mkdir %t
+# RUN: rm -rf %t; split-file %s %t
 
-# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/main.o
-# RUN: %lld -lSystem --icf=all -o %t/main %t/main.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 %t/main.s -o %t/main.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin19.0.0 %t/abs.s -o %t/abs.o
+# RUN: %lld -pie -lSystem --icf=all -o %t/main %t/main.o %t/abs.o
 # RUN: llvm-objdump -d --syms %t/main | FileCheck %s
 
 # CHECK-LABEL: SYMBOL TABLE:
 # CHECK:       [[#%x,MAIN:]] g   F __TEXT,__text _main
 # CHECK:       [[#%x,A:]]    g   F __TEXT,__text _a1
+# CHECK:       [[#%x,H:]]    g   F __TEXT,__text _h
 # CHECK:       [[#%x,A]]     g   F __TEXT,__text _a2
+# CHECK:       [[#%x,A]]     g   F __TEXT,__text _a3
+# CHECK:       [[#%x,B:]]    g   F __TEXT,__text _b
 # CHECK:       [[#%x,C:]]    g   F __TEXT,__text _c
 # CHECK:       [[#%x,D:]]    g   F __TEXT,__text _d
 # CHECK:       [[#%x,E:]]    g   F __TEXT,__text _e
 # CHECK:       [[#%x,F:]]    g   F __TEXT,__text _f
 # CHECK:       [[#%x,G:]]    g   F __TEXT,__text _g
+# CHECK:       [[#%x,I:]]    g   F __TEXT,__text _i
+# CHECK:       [[#%x,J:]]    g   F __TEXT,__text _j
 # CHECK:       [[#%x,SR:]]   g   F __TEXT,__text _sr1
 # CHECK:       [[#%x,SR]]    g   F __TEXT,__text _sr2
 # CHECK:       [[#%x,MR:]]   g   F __TEXT,__text _mr1
 # CHECK:       [[#%x,MR]]    g   F __TEXT,__text _mr2
 ### FIXME: Mutually-recursive functions with identical bodies (see below)
 # COM:         [[#%x,XR:]]   g   F __TEXT,__text _xr1
 # COM:         [[#%x,XR]]    g   F __TEXT,__text _xr2
 
 # CHECK-LABEL: Disassembly of section __TEXT,__text:
 # CHECK:       [[#%x,MAIN]] <_main>:
-# CHECK-NEXT:  callq 0x[[#%x,A]]  <_a2>
-# CHECK-NEXT:  callq 0x[[#%x,A]]  <_a2>
+# CHECK-NEXT:  callq 0x[[#%x,A]]  <_a3>
+# CHECK-NEXT:  callq 0x[[#%x,A]]  <_a3>
+# CHECK-NEXT:  callq 0x[[#%x,A]]  <_a3>
+# CHECK-NEXT:  callq 0x[[#%x,B]]  <_b>
 # CHECK-NEXT:  callq 0x[[#%x,C]]  <_c>
 # CHECK-NEXT:  callq 0x[[#%x,D]]  <_d>
 # CHECK-NEXT:  callq 0x[[#%x,E]]  <_e>
 # CHECK-NEXT:  callq 0x[[#%x,F]]  <_f>
 # CHECK-NEXT:  callq 0x[[#%x,G]]  <_g>
+# CHECK-NEXT:  callq 0x[[#%x,H]]  <_h>
+# CHECK-NEXT:  callq 0x[[#%x,I]]  <_i>
+# CHECK-NEXT:  callq 0x[[#%x,J]]  <_j>
 # CHECK-NEXT:  callq 0x[[#%x,SR]] <_sr2>
 # CHECK-NEXT:  callq 0x[[#%x,SR]] <_sr2>
 # CHECK-NEXT:  callq 0x[[#%x,MR]] <_mr2>
 # CHECK-NEXT:  callq 0x[[#%x,MR]] <_mr2>
 ### FIXME: Mutually-recursive functions with identical bodies (see below)
 # COM-NEXT:    callq 0x[[#%x,XR]] <_xr2>
 # COM-NEXT:    callq 0x[[#%x,XR]] <_xr2>
 
 ### TODO:
 ### * Fold: funcs only differ in alignment
-### * No fold: func has personality/LSDA
-### * No fold: reloc references to absolute symbols with different values
 ### * No fold: func is weak? preemptable?
-### * No fold: relocs to N_ALT_ENTRY symbols
 
+#--- abs.s
+.subsections_via_symbols
+
+.globl _abs1a, _abs1b, _abs2
+_abs1a = 0xfeedfac3
+_abs1b = 0xfeedfac3
+_abs2 =  0xfeedf00d
+
+#--- main.s
 .subsections_via_symbols
 .text
+.globl _h
+.alt_entry _h
 
 ### Fold: _a1 & _a2 have identical bodies, flags, relocs
 
 .globl _a1
-.p2align 4, 0x90
+.p2align 2
 _a1:
   callq _d
+### No fold: _h is an alt entry past _a1
+_h:
   mov ___nan@GOTPCREL(%rip), %rax
   callq ___isnan
+  movabs $_abs1a, %rdx
   movl $0, %eax
   ret
 
 .globl _a2
-.p2align 4, 0x90
+.p2align 2
 _a2:
   callq _d
   mov ___nan@GOTPCREL(%rip), %rax
   callq ___isnan
+  movabs $_abs1a, %rdx
+  movl $0, %eax
+  ret
+
+### Fold: reference to absolute symbol with different name but identical value
+
+.globl _a3
+.p2align 2
+_a3:
+  callq _d
+  mov ___nan@GOTPCREL(%rip), %rax
+  callq ___isnan
+  movabs $_abs1b, %rdx
+  movl $0, %eax
+  ret
+
+### No fold: the absolute symbol reference differs
+
+.globl _b
+.p2align 2
+_b:
+  callq _d
+  mov ___nan@GOTPCREL(%rip), %rax
+  callq ___isnan
+  movabs $_abs2, %rdx
   movl $0, %eax
   ret
 
 ### No fold: _c has slightly different body from _a1 & _a2
 
 .globl _c
-.p2align 4, 0x90
+.p2align 2
 _c:
   callq _d
   mov ___nan@GOTPCREL(%rip), %rax
   callq ___isnan
+  movabs $_abs1a, %rdx
   movl $1, %eax
   ret
 
 ### No fold: _d has the same body as _a1 & _a2, but _d is recursive!
 
 .globl _d
-.p2align 4, 0x90
+.p2align 2
 _d:
   callq _d
   mov ___nan@GOTPCREL(%rip), %rax
   callq ___isnan
+  movabs $_abs1a, %rdx
   movl $0, %eax
   ret
 
-### No fold: the body of _e is longer
+### No fold: the function body is longer
 
 .globl _e
-.p2align 4, 0x90
+.p2align 2
 _e:
   callq _d
   mov ___nan@GOTPCREL(%rip), %rax
   callq ___isnan
+  movabs $_abs1a, %rdx
   movl $0, %eax
   ret
   nop
 
-### No fold: the dylib symbols differ
+### No fold: GOT referent dylib symbol differs
 
 .globl _f
-.p2align 4, 0x90
+.p2align 2
 _f:
   callq _d
   mov ___inf@GOTPCREL(%rip), %rax
   callq ___isnan
+  movabs $_abs1a, %rdx
   movl $0, %eax
   ret
 
+### No fold: call referent dylib symbol differs
+
 .globl _g
-.p2align 4, 0x90
+.p2align 2
 _g:
   callq _d
-  mov ___inf@GOTPCREL(%rip), %rax
+  mov ___nan@GOTPCREL(%rip), %rax
   callq ___isinf
+  movabs $_abs1a, %rdx
+  movl $0, %eax
+  ret
+
+### No fold: functions have personality and/or LSDA
+### Mere presence of personality and/or LSDA isolates a function into its own
+### equivalence class. We don't care if two functions happen to have identical
+### personality & LSDA.
+
+.globl _i
+.p2align 2
+_i:
+  .cfi_startproc
+  .cfi_personality 155, _my_personality0
+  .cfi_lsda 16, _exception0
+  .cfi_def_cfa_offset 16
+  callq _d
+  mov ___nan@GOTPCREL(%rip), %rax
+  callq ___isnan
+  movabs $_abs1a, %rdx
+  movl $0, %eax
+  ret
+  .cfi_endproc
+
+.globl _j
+.p2align 2
+_j:
+  .cfi_startproc
+  .cfi_personality 155, _my_personality0
+  .cfi_lsda 16, _exception0
+  .cfi_def_cfa_offset 16
+  callq _d
+  mov ___nan@GOTPCREL(%rip), %rax
+  callq ___isnan
+  movabs $_abs1a, %rdx
   movl $0, %eax
   ret
+  .cfi_endproc
 
 ### Fold: Simple recursion
 
 .globl _sr1
-.p2align 4, 0x90
+.p2align 2
 _sr1:
   callq _sr1
-  movl $2, %eax
+  movl $0, %eax
   ret
 
 .globl _sr2
-.p2align 4, 0x90
+.p2align 2
 _sr2:
   callq _sr2
-  movl $2, %eax
+  movl $0, %eax
   ret
 
 ### Fold: Mutually-recursive functions with symmetric bodies
 
 .globl _mr1
-.p2align 4, 0x90
+.p2align 2
 _mr1:
   callq _mr1 # call myself
   callq _mr2 # call my twin
-  movl $1, %eax
+  movl $0, %eax
   ret
 
 .globl _mr2
-.p2align 4, 0x90
+.p2align 2
 _mr2:
   callq _mr2 # call myself
   callq _mr1 # call my twin
-  movl $1, %eax
+  movl $0, %eax
   ret
 
 ### Fold: Mutually-recursive functions with identical bodies
 ###
 ### FIXME: This test is currently broken. Recursive call sites have no relocs
 ### and the non-zero displacement field is already written to the section
 ### data, while non-recursive call sites use symbol relocs and section data
 ### contains zeros in the displacement field. Thus, ICF's equalsConstant()
 ### finds that the section data doesn't match.
 ###
 ### ELF folds this case properly because it emits symbol relocs for all calls,
 ### even recursive ones.
 
 .globl _xr1
-.p2align 4, 0x90
+.p2align 2
 _xr1:
   callq _xr1 # call myself
   callq _xr2 # call my twin
   movl $3, %eax
   ret
 
 .globl _xr2
-.p2align 4, 0x90
+.p2align 2
 _xr2:
   callq _xr1 # call my twin
   callq _xr2 # call myself
   movl $3, %eax
   ret
 
 ###
 
 .globl _main
-.p2align 4, 0x90
+.p2align 2
 _main:
   callq _a1
   callq _a2
+  callq _a3
+  callq _b
   callq _c
   callq _d
   callq _e
   callq _f
   callq _g
+  callq _h
+  callq _i
+  callq _j
   callq _sr1
   callq _sr2
   callq _mr1
   callq _mr2
   callq _xr1
   callq _xr2
   ret
+
+.globl _my_personality0
+.p2align 2
+_my_personality0:
+  movl $0, %eax
+  ret
+
+.section __TEXT,__gcc_except_tab
+.globl _exception0
+_exception0:
+  .space 1