[GlobalISel] Fix infinite loop in reassociationCanBreakAddressingModePattern

[paquette]

Summary

It didn't update the opcode while walking through G_INTTOPTR/G_PTRTOINT.

[aemerson]

LGTM, thanks.

llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

for (auto &UseMI : MRI.use_nodbg_instructions(Src1Reg)) {
     MachineInstr *ConvUseMI = &UseMI;
     unsigned ConvUseOpc = ConvUseMI->getOpcode();
     while (ConvUseOpc == TargetOpcode::G_INTTOPTR ||
            ConvUseOpc == TargetOpcode::G_PTRTOINT) {
       Register DefReg = ConvUseMI->getOperand(0).getReg();
       if (!MRI.hasOneNonDBGUse(DefReg))
         break;
       ConvUseMI = &*MRI.use_instr_nodbg_begin(DefReg);
+      ConvUseOpc = ConvUseMI->getOpcode();
     }
     auto LoadStore = ConvUseOpc == TargetOpcode::G_LOAD ||
                      ConvUseOpc == TargetOpcode::G_STORE;
     if (!LoadStore)
       continue;
     // Is x[offset2] already not a legal addressing mode? If so then
     // reassociating the constants breaks nothing (we test offset2 because
     // that's the one we hope to fold into the load or store).

llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-reassociation.mir

bb.1:
     %2:_(s64) = G_CONSTANT i64 1
     %3:_(s64) = G_ADD %1, %2
     %4:_(p0) = G_PTR_ADD %0, %3(s64)
     %7:_(s32) = G_LOAD %4(p0) :: (load 1)
     $w0 = COPY %7(s32)
     RET_ReallyLR implicit $w0
 
 ...
+---
+name:            walk_through_inttoptr
+alignment:       4
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $x0
+    ; CHECK-LABEL: name: walk_through_inttoptr
+    ; CHECK: liveins: $x0
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 4777
+    ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 6
+    ; CHECK: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+    ; CHECK: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C]](s64)
+    ; CHECK: %ptr_to_int:_(s64) = G_PTRTOINT [[PTR_ADD]](p0)
+    ; CHECK: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[PTR_ADD]], [[C1]](s64)
+    ; CHECK: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD1]](p0) :: (load (s32))
+    ; CHECK: G_STORE [[C2]](s32), [[PTR_ADD]](p0) :: (store (s32))
+    ; CHECK: G_STORE %ptr_to_int(s64), [[PTR_ADD]](p0) :: (store (s64))
+    ; CHECK: $w0 = COPY [[LOAD]](s32)
+    ; CHECK: RET_ReallyLR implicit $w0
+    %0:_(p0) = COPY $x0
+    %2:_(s64) = G_CONSTANT i64 4777
+    %4:_(s64) = G_CONSTANT i64 6
+    %9:_(s32) = G_CONSTANT i32 0
+    %10:_(p0) = G_PTR_ADD %0, %2(s64)
+    %ptr_to_int:_(s64) = G_PTRTOINT %10
+    %11:_(p0) = G_PTR_ADD %10, %4(s64)
+    %7:_(s32) = G_LOAD %11(p0) :: (load 4)
+    G_STORE %9(s32), %10(p0) :: (store 4) ; other use of %10
+    G_STORE %ptr_to_int(s64), %10(p0) :: (store 8)
+    $w0 = COPY %7(s32)
+    RET_ReallyLR implicit $w0