[llvm] [Thumb,ELF] Fix access to dso_preemptable __stack_chk_guard with static relocation model (PR #78950)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-arm

Author: Fangrui Song (MaskRay)

<details>
<summary>Changes</summary>

After #<!-- -->70014, A32 correctly uses GOT for dso_preemptable
`__stack_chk_guard` with static relocation model (e.g. -fPIE/-fPIC LTO
compiles with -no-pie linking).

This patch fixes Thumb1 and Thumb2.

Fix #<!-- -->64999


---
Full diff: https://github.com/llvm/llvm-project/pull/78950.diff


3 Files Affected:

- (modified) llvm/lib/Target/ARM/Thumb1InstrInfo.cpp (+3-2) 
- (modified) llvm/lib/Target/ARM/Thumb2InstrInfo.cpp (+1-1) 
- (modified) llvm/test/CodeGen/ARM/stack-guard-elf.ll (+24-6) 


``````````diff
diff --git a/llvm/lib/Target/ARM/Thumb1InstrInfo.cpp b/llvm/lib/Target/ARM/Thumb1InstrInfo.cpp
index e2f3fad20079047..e3104e8ee765f9c 100644
--- a/llvm/lib/Target/ARM/Thumb1InstrInfo.cpp
+++ b/llvm/lib/Target/ARM/Thumb1InstrInfo.cpp
@@ -135,14 +135,15 @@ void Thumb1InstrInfo::loadRegFromStackSlot(MachineBasicBlock &MBB,
 void Thumb1InstrInfo::expandLoadStackGuard(
     MachineBasicBlock::iterator MI) const {
   MachineFunction &MF = *MI->getParent()->getParent();
-  const TargetMachine &TM = MF.getTarget();
   const ARMSubtarget &ST = MF.getSubtarget<ARMSubtarget>();
+  const GlobalValue *GV =
+      cast<GlobalValue>((*MI->memoperands_begin())->getValue());
 
   assert(MF.getFunction().getParent()->getStackProtectorGuard() != "tls" &&
          "TLS stack protector not supported for Thumb1 targets");
 
   unsigned Instr;
-  if (TM.isPositionIndependent())
+  if (!GV->isDSOLocal())
     Instr = ARM::tLDRLIT_ga_pcrel;
   else if (ST.genExecuteOnly() && ST.hasV8MBaselineOps())
     Instr = ARM::t2MOVi32imm;
diff --git a/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp b/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
index 2ea0eaa0aad8f56..9e4b51616b56ecc 100644
--- a/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
+++ b/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
@@ -264,7 +264,7 @@ void Thumb2InstrInfo::expandLoadStackGuard(
   const GlobalValue *GV =
       cast<GlobalValue>((*MI->memoperands_begin())->getValue());
 
-  if (MF.getSubtarget<ARMSubtarget>().isGVInGOT(GV))
+  if (!GV->isDSOLocal())
     expandLoadStackGuardBase(MI, ARM::t2LDRLIT_ga_pcrel, ARM::t2LDRi12);
   else if (MF.getTarget().isPositionIndependent())
     expandLoadStackGuardBase(MI, ARM::t2MOV_ga_pcrel, ARM::t2LDRi12);
diff --git a/llvm/test/CodeGen/ARM/stack-guard-elf.ll b/llvm/test/CodeGen/ARM/stack-guard-elf.ll
index 250f2ad9ed1093b..d0e5db7e5711b0c 100644
--- a/llvm/test/CodeGen/ARM/stack-guard-elf.ll
+++ b/llvm/test/CodeGen/ARM/stack-guard-elf.ll
@@ -59,6 +59,8 @@ define i32 @test1() #0 {
 ; THUMB1-NEXT:    .pad #16
 ; THUMB1-NEXT:    sub sp, #16
 ; THUMB1-NEXT:    ldr r0, .LCPI0_0
+; THUMB1-NEXT:  .LPC0_0:
+; THUMB1-NEXT:    add r0, pc
 ; THUMB1-NEXT:    ldr r0, [r0]
 ; THUMB1-NEXT:    ldr r0, [r0]
 ; THUMB1-NEXT:    add r1, sp, #904
@@ -67,7 +69,9 @@ define i32 @test1() #0 {
 ; THUMB1-NEXT:    bl foo
 ; THUMB1-NEXT:    add r0, sp, #904
 ; THUMB1-NEXT:    ldr r0, [r0, #124]
-; THUMB1-NEXT:    ldr r1, .LCPI0_0
+; THUMB1-NEXT:    ldr r1, .LCPI0_1
+; THUMB1-NEXT:  .LPC0_1:
+; THUMB1-NEXT:    add r1, pc
 ; THUMB1-NEXT:    ldr r1, [r1]
 ; THUMB1-NEXT:    ldr r1, [r1]
 ; THUMB1-NEXT:    cmp r1, r0
@@ -83,7 +87,11 @@ define i32 @test1() #0 {
 ; THUMB1-NEXT:    .p2align 2
 ; THUMB1-NEXT:  @ %bb.3:
 ; THUMB1-NEXT:  .LCPI0_0:
-; THUMB1-NEXT:    .long __stack_chk_guard
+; THUMB1-NEXT:  .Ltmp0:
+; THUMB1-NEXT:    .long __stack_chk_guard(GOT_PREL)-((.LPC0_0+4)-.Ltmp0)
+; THUMB1-NEXT:  .LCPI0_1:
+; THUMB1-NEXT:  .Ltmp1:
+; THUMB1-NEXT:    .long __stack_chk_guard(GOT_PREL)-((.LPC0_1+4)-.Ltmp1)
 ;
 ; THUMB1-PIC-LABEL: test1:
 ; THUMB1-PIC:       @ %bb.0:
@@ -136,16 +144,18 @@ define i32 @test1() #0 {
 ; THUMB2-NEXT:    push {r7, lr}
 ; THUMB2-NEXT:    .pad #1032
 ; THUMB2-NEXT:    sub.w sp, sp, #1032
-; THUMB2-NEXT:    movw r0, :lower16:__stack_chk_guard
-; THUMB2-NEXT:    movt r0, :upper16:__stack_chk_guard
+; THUMB2-NEXT:    ldr r0, .LCPI0_0
+; THUMB2-NEXT:  .LPC0_0:
+; THUMB2-NEXT:    add r0, pc
 ; THUMB2-NEXT:    ldr r0, [r0]
 ; THUMB2-NEXT:    ldr r0, [r0]
 ; THUMB2-NEXT:    str.w r0, [sp, #1028]
 ; THUMB2-NEXT:    add r0, sp, #4
 ; THUMB2-NEXT:    bl foo
-; THUMB2-NEXT:    movw r1, :lower16:__stack_chk_guard
 ; THUMB2-NEXT:    ldr.w r0, [sp, #1028]
-; THUMB2-NEXT:    movt r1, :upper16:__stack_chk_guard
+; THUMB2-NEXT:    ldr r1, .LCPI0_1
+; THUMB2-NEXT:  .LPC0_1:
+; THUMB2-NEXT:    add r1, pc
 ; THUMB2-NEXT:    ldr r1, [r1]
 ; THUMB2-NEXT:    ldr r1, [r1]
 ; THUMB2-NEXT:    cmp r1, r0
@@ -155,6 +165,14 @@ define i32 @test1() #0 {
 ; THUMB2-NEXT:    popeq {r7, pc}
 ; THUMB2-NEXT:  .LBB0_1:
 ; THUMB2-NEXT:    bl __stack_chk_fail
+; THUMB2-NEXT:    .p2align 2
+; THUMB2-NEXT:  @ %bb.2:
+; THUMB2-NEXT:  .LCPI0_0:
+; THUMB2-NEXT:  .Ltmp0:
+; THUMB2-NEXT:    .long __stack_chk_guard(GOT_PREL)-((.LPC0_0+4)-.Ltmp0)
+; THUMB2-NEXT:  .LCPI0_1:
+; THUMB2-NEXT:  .Ltmp1:
+; THUMB2-NEXT:    .long __stack_chk_guard(GOT_PREL)-((.LPC0_1+4)-.Ltmp1)
 ;
 ; THUMB2-PIC-LABEL: test1:
 ; THUMB2-PIC:       @ %bb.0:

``````````

</details>


https://github.com/llvm/llvm-project/pull/78950