[llvm] [ARM] Record store with pre/post-indexed addressing as `mayStore` (PR #121565)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-arm

Author: Antonio Frighetto (antoniofrighetto)

<details>
<summary>Changes</summary>

A miscompilation issue observed during machine sinking has been addressed with improved handling.

Fixes: https://github.com/llvm/llvm-project/issues/121299.

---
Full diff: https://github.com/llvm/llvm-project/pull/121565.diff


2 Files Affected:

- (modified) llvm/lib/Target/ARM/ARMInstrInfo.td (+2-1) 
- (added) llvm/test/CodeGen/ARM/sink-store-pre-load-dependency.mir (+41) 


``````````diff
diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index c67177cd5a6fea..009b60c8400f02 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -3320,7 +3320,7 @@ def STRH_preidx: ARMPseudoInst<(outs GPR:$Rn_wb),
 }
 
 
-
+let mayStore = 1, hasSideEffects = 0 in {
 def STRH_PRE  : AI3ldstidx<0b1011, 0, 1, (outs GPR:$Rn_wb),
                            (ins GPR:$Rt, addrmode3_pre:$addr), IndexModePre,
                            StMiscFrm, IIC_iStore_bh_ru,
@@ -3352,6 +3352,7 @@ def STRH_POST : AI3ldstidx<0b1011, 0, 0, (outs GPR:$Rn_wb),
   let Inst{3-0}   = offset{3-0};    // imm3_0/Rm
   let DecoderMethod = "DecodeAddrMode3Instruction";
 }
+} // mayStore = 1, hasSideEffects = 0
 
 let mayStore = 1, hasSideEffects = 0, hasExtraSrcRegAllocReq = 1 in {
 def STRD_PRE : AI3ldstidx<0b1111, 0, 1, (outs GPR:$Rn_wb),
diff --git a/llvm/test/CodeGen/ARM/sink-store-pre-load-dependency.mir b/llvm/test/CodeGen/ARM/sink-store-pre-load-dependency.mir
new file mode 100644
index 00000000000000..92c983e2bfd1da
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/sink-store-pre-load-dependency.mir
@@ -0,0 +1,41 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -o - %s -mtriple=armv7-- -run-pass=machine-sink | FileCheck %s
+
+name: sink-store-load-dep
+tracksRegLiveness: true
+stack:
+  - { id: 0, type: default, size: 8, alignment: 8 }
+body: |
+  bb.0:
+    ; CHECK-LABEL: name: sink-store-load-dep
+    ; CHECK:       bb.0:
+    ; CHECK:         [[LDRi12_:%[0-9]+]]:gpr = LDRi12 %stack.0, 0, 14 /* CC::al */, $noreg :: (load (s32))
+    ; CHECK-NEXT:    [[MOVi:%[0-9]+]]:gpr = MOVi 55296, 14 /* CC::al */, $noreg, $noreg
+    ; CHECK-NEXT:    [[ADDri1:%[0-9]+]]:gpr = ADDri [[LDRi12_:%[0-9]+]], 0, 14 /* CC::al */, $noreg, $noreg
+    ; CHECK-NEXT:    [[LDRH:%[0-9]+]]:gpr = LDRH killed [[ADDri1:%[0-9]+]], $noreg, 0, 14 /* CC::al */, $noreg :: (load (s16))
+    ; CHECK-NEXT:    [[MOVi1:%[0-9]+]]:gpr = MOVi 0, 14 /* CC::al */, $noreg, $noreg
+    ; CHECK-NEXT:    early-clobber %5:gpr = STRH_PRE [[MOVi:%[0-9]+]], [[LDRi12_:%[0-9]+]], [[MOVi1:%[0-9]+]], 0, 14 /* CC::al */, $noreg
+    ; CHECK-NEXT:    [[SUBri:%.*]]:gpr = SUBri killed [[LDRi12_:%[0-9]+]], 0, 14 /* CC::al */, $noreg, $noreg
+    ; CHECK:       bb.2:
+    ; CHECK-NEXT:    [[MOVi2:%[0-9]+]]:gpr = MOVi [[LDRH:%[0-9]+]], 14 /* CC::al */, $noreg, $noreg
+    %0:gpr = LDRi12 %stack.0, 0, 14, $noreg :: (load (s32))
+    %1:gpr = MOVi 55296, 14, $noreg, $noreg
+    %2:gpr = ADDri %0:gpr, 0, 14, $noreg, $noreg
+    %3:gpr = LDRH killed %2:gpr, $noreg, 0, 14, $noreg :: (load (s16))
+    %4:gpr = MOVi 0, 14, $noreg, $noreg
+    early-clobber %5:gpr = STRH_PRE %1:gpr, %0:gpr, %4:gpr, 0, 14, $noreg
+    %6:gpr = SUBri killed %0:gpr, 0, 14, $noreg, $noreg
+    CMPri %6:gpr, 0, 14, $noreg, implicit-def $cpsr
+    Bcc %bb.2, 3, $cpsr
+    B %bb.1
+
+  bb.1:
+    %8:gpr = MOVi 0, 14, $noreg, $noreg
+    $r0 = COPY %8:gpr
+    BX_RET 14, $noreg, implicit $r0
+
+  bb.2:
+    %9:gpr = MOVi %3:gpr, 14, $noreg, $noreg
+    $r0 = COPY %9:gpr
+    BX_RET 14, $noreg, implicit $r0
+...

``````````

</details>


https://github.com/llvm/llvm-project/pull/121565