[GlobalISel] Fix miscompile of G_UREM + G_UDIV due to not checking for equality of the first operands of each.

[aemerson]

Summary

Fixes issue #55287

[paquette]

LGTM

llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

bool CombinerHelper::matchCombineDivRem(MachineInstr &MI,
   //   %div:_ = G_[SU]DIV %src1:_, %src2:_
   // into:
   //  %div:_, %rem:_ = G_[SU]DIVREM %src1:_, %src2:_
 
   for (auto &UseMI : MRI.use_nodbg_instructions(Src1)) {
     if (MI.getParent() == UseMI.getParent() &&
         ((IsDiv && UseMI.getOpcode() == RemOpcode) ||
          (!IsDiv && UseMI.getOpcode() == DivOpcode)) &&
-        matchEqualDefs(MI.getOperand(2), UseMI.getOperand(2))) {
+        matchEqualDefs(MI.getOperand(2), UseMI.getOperand(2)) &&
+        matchEqualDefs(MI.getOperand(1), UseMI.getOperand(1))) {
       OtherMI = &UseMI;
       return true;
     }
   }
 
   return false;
 }
 

llvm/test/CodeGen/AArch64/GlobalISel/combine-udivrem-use-bug.mir

+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -o - -mtriple=aarch64-unknown-unknown -run-pass=aarch64-prelegalizer-combiner -verify-machineinstrs %s | FileCheck %s
+# Check that we don't miscompile this into G_UDIVREM because of the different
+# first operands.
+---
+name:            no_combine_divrem_different_src1
+body:             |
+  bb.1:
+    liveins: $w0
+
+    ; CHECK-LABEL: name: no_combine_divrem_different_src1
+    ; CHECK: liveins: $w0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY $w0
+    ; CHECK-NEXT: [[UREM:%[0-9]+]]:_(s32) = G_UREM [[COPY]], [[COPY]]
+    ; CHECK-NEXT: [[UDIV:%[0-9]+]]:_(s32) = G_UDIV [[UREM]], [[COPY]]
+    ; CHECK-NEXT: $w0 = COPY [[UDIV]](s32)
+    ; CHECK-NEXT: RET_ReallyLR implicit $w0
+    %0:_(s32) = COPY $w0
+    %1:_(s32) = G_UREM %0, %0
+    %2:_(s32) = G_UDIV %1, %0
+    $w0 = COPY %2(s32)
+    RET_ReallyLR implicit $w0
+
+...