[SystemZ] Avoid type legalization on structs

[cuviper]

Summary

In SystemZTTIImpl::getMemoryOpCost, the call to getNumberOfParts will
run type legalization, which can't handle structs. So before that, we
check for an unknown value type and forward to BaseT, just like many
other targets do in this situation.

https://bugzilla.redhat.com/show_bug.cgi?id=2224885

[uweigand]

LGTM, thanks!

llvm/lib/Target/SystemZ/SystemZTargetTransformInfo.cpp

if (isFoldableLoad(cast<LoadInst>(I), FoldedValue)) {
             return i == 0; // Both operands foldable.
         }
       }
 
       return 0; // Only I is foldable in user.
     }
   }
 
+  // Type legalization (via getNumberOfParts) can't handle structs
+  if (TLI->getValueType(DL, Src, true) == MVT::Other)
+    return BaseT::getMemoryOpCost(Opcode, Src, Alignment, AddressSpace,
+                                  CostKind);
+
   unsigned NumOps =
     (Src->isVectorTy() ? getNumVectorRegs(Src) : getNumberOfParts(Src));
 
   // Store/Load reversed saves one instruction.
   if (((!Src->isVectorTy() && NumOps == 1) || ST->hasVectorEnhancements2()) &&
       I != nullptr) {
     if (Opcode == Instruction::Load && I->hasOneUse()) {
       const Instruction *LdUser = cast<Instruction>(*I->user_begin());

llvm/test/Analysis/CostModel/SystemZ/struct-cost-crash.ll

+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 2
+; RUN: opt -passes="print<cost-model>" 2>&1 -disable-output < %s | FileCheck %s
+;
+; Check that SystemZTTIImpl::getMemoryOpCost doesn't try to legalize structs,
+; which was failing llvm_unreachable in MVT::getVT.
+
+target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
+target triple = "s390x-unknown-linux-gnu"
+
+declare { i64, i32 } @bar()
+
+define i8 @foo() {
+; CHECK-LABEL: 'foo'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %1
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: %2 = call { i64, i32 } @bar()
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: store { i64, i32 } %2, ptr inttoptr (i64 16 to ptr), align 16
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: br label %1
+;
+  br label %1
+
+1:                                                ; preds = %1, %0
+  %2 = call { i64, i32 } @bar()
+  store { i64, i32 } %2, ptr inttoptr (i64 16 to ptr), align 16
+  br label %1
+}