[ARM] [ELF] Fix ARMMaterializeGV for Indirect calls

[zatrazz]

Summary

Recent shouldAssumeDSOLocal changes (introduced by 961f31d8ad14c66)
do not take in consideration the relocation model anymore. The ARM
fast-isel pass uses the function return to set whether a global symbol
is loaded indirectly or not, and without the expected information
llvm now generates an extra load for following code:

$ cat test.ll
@__asan_option_detect_stack_use_after_return = external global i32
define dso_local i32 @main(i32 %argc, i8** %argv) #0 {
entry:
  %0 = load i32, i32* @__asan_option_detect_stack_use_after_return,
align 4
  %1 = icmp ne i32 %0, 0
  br i1 %1, label %2, label %3

2:
  ret i32 0

3:
  ret i32 1
}

attributes #0 = { noinline optnone }

$ lcc test.ll -o -
[...]
main:
        .fnstart
[...]
        movw    r0, :lower16:__asan_option_detect_stack_use_after_return
        movt    r0, :upper16:__asan_option_detect_stack_use_after_return
        ldr     r0, [r0]
        ldr     r0, [r0]
        cmp     r0, #0
[...]

And without 'optnone' it produces:

[...]
main:
        .fnstart
[...]
        movw    r0, :lower16:__asan_option_detect_stack_use_after_return
        movt    r0, :upper16:__asan_option_detect_stack_use_after_return
        ldr     r0, [r0]
        clz     r0, r0
        lsr     r0, r0, #5
        bx      lr

[...]

This triggered a lot of invalid memory access in sanitizers for
arm-linux-gnueabihf. I checked this patch both a stage1 built with
gcc and a stage2 bootstrap and it fixes all the Linux sanitizers
issues.

[MaskRay]

Thanks!

We could make -fdirect-access-external-data create a module metadata to make declarations automatically dso_local, but I am not sure that is useful (can cause copy relocations/canonical PLT entries if the symbol is defined externally)

llvm/lib/Target/ARM/ARMFastISel.cpp

if (isThumb2) {
                                   .addReg(DestReg)
                                   .addImm(Id);
         AddOptionalDefs(MIB);
         return NewDestReg;
       }
     }
   }
 
-  if (IsIndirect) {
+  if ((Subtarget->isTargetELF() && Subtarget->isGVInGOT(GV)) ||
+      (Subtarget->isTargetMachO() && IsIndirect) ||
+      Subtarget->genLongCalls()) {
     MachineInstrBuilder MIB;
     unsigned NewDestReg = createResultReg(TLI.getRegClassFor(VT));
     if (isThumb2)
       MIB = BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
                     TII.get(ARM::t2LDRi12), NewDestReg)
             .addReg(DestReg)
             .addImm(0);
     else

llvm/test/CodeGen/ARM/fast-isel-intrinsic.ll

 ; ARM-MACHO: {{(movw r0, :lower16:L_temp\$non_lazy_ptr)|(ldr r0, .LCPI)}}
 ; ARM-MACHO: {{(movt r0, :upper16:L_temp\$non_lazy_ptr)?}}
 ; ARM-MACHO: ldr [[REG1:r[0-9]+]], [r0]
 ; ARM-MACHO:      add r0, [[REG1]], #4
 ; ARM-MACHO-NEXT: add r1, [[REG1]], #16
 
 ; ARM-ELF: movw [[REG1:r[0-9]+]], :lower16:temp
 ; ARM-ELF: movt [[REG1]], :upper16:temp
-; ARM-ELF:      add [[REG1]], r1, #4
-; ARM-ELF-NEXT: add r1, r1, #16
+; ARM-ELF:      add r0, [[REG1]], #4
+; ARM-ELF-NEXT: add r1, [[REG1]], #16
 
 ; ARM: movw r2, #17
 ; ARM: bl {{_?}}memcpy
 ; ARM-LONG-LABEL: t2:
 
 ; ARM-LONG-MACHO: {{(movw r3, :lower16:L_memcpy\$non_lazy_ptr)|(ldr r3, .LCPI)}}
 ; ARM-LONG-MACHO: {{(movt r3, :upper16:L_memcpy\$non_lazy_ptr)?}}
 ; ARM-LONG-MACHO: ldr r3, [r3]

 ; ARM-MACHO: {{(movw r0, :lower16:L_temp\$non_lazy_ptr)|(ldr r0, .LCPI)}}
 ; ARM-MACHO: {{(movt r0, :upper16:L_temp\$non_lazy_ptr)?}}
 ; ARM-MACHO: ldr [[REG0:r[0-9]+]], [r0]
 ; ARM-MACHO:      add r0, [[REG0]], #4
 ; ARM-MACHO-NEXT: add r1, [[REG0]], #16
 
 ; ARM-ELF: movw [[REG0:r[0-9]+]], :lower16:temp
 ; ARM-ELF: movt [[REG0]], :upper16:temp
-; ARM-ELF:      add [[REG0]], r1, #4
+; ARM-ELF:      add r0, [[REG0]], #4
 ; ARM-ELF-NEXT: add r1, r1, #16
 
 ; ARM: movw r2, #10
 ; ARM: bl {{_?}}memmove
 ; ARM-LONG-LABEL: t3:
 
 ; ARM-LONG-MACHO: {{(movw r3, :lower16:L_memmove\$non_lazy_ptr)|(ldr r3, .LCPI)}}
 ; ARM-LONG-MACHO: {{(movt r3, :upper16:L_memmove\$non_lazy_ptr)?}}