[GlobalISel] Disable GISel for big endian

[aemerson]

Summary

This is due to PR26161 needing to be resolved before we can fix big endian bugs like PR35359. The work to split aggregates into smaller LLTs instead of using one large scalar will take some time, so in the mean time we'll fall back to SDAG.

Some ARM BE tests xfailed for now as a result.

[aemerson]

Ping.

[kristof.beyls]

I'll let @rovka review the code; I just thought I'd add @ivanbaev as a subscriber, as I believe he's a user of big endian code generation on Arm/AArch64 to be aware that this means that when globalisel gets enabled by default on AArch64 at -O0, it'll in practice only be for little endian, not big endian.
I'm wondering if a test case could be added to test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll, so that test keeps on being a reasonable representation of fallbacks that need to be fixed eventually.

[aemerson]

Thanks, I've added a new fallback test.

[rovka]

LGTM until we can handle big endian. Sorry about the delay.

llvm/trunk/lib/CodeGen/GlobalISel/IRTranslator.cpp

bool IRTranslator::runOnMachineFunction(MachineFunction &CurMF) {
   EntryBuilder.setMF(*MF);
   MRI = &MF->getRegInfo();
   DL = &F.getParent()->getDataLayout();
   TPC = &getAnalysis<TargetPassConfig>();
   ORE = llvm::make_unique<OptimizationRemarkEmitter>(&F);
 
   assert(PendingPHIs.empty() && "stale PHIs");
 
+  if (!DL->isLittleEndian()) {
+    // Currently we don't properly handle big endian code.
+    OptimizationRemarkMissed R("gisel-irtranslator", "GISelFailure",
+                               MF->getFunction()->getSubprogram(),
+                               &MF->getFunction()->getEntryBlock());
+    R << "unable to translate in big endian mode";
+    reportTranslationError(*MF, *TPC, *ORE, R);
+  }
+
   // Release the per-function state when we return, whether we succeeded or not.
   auto FinalizeOnReturn = make_scope_exit([this]() { finalizeFunction(); });
 
   // Setup a separate basic-block for the arguments and constants
   MachineBasicBlock *EntryBB = MF->CreateMachineBasicBlock();
   MF->push_back(EntryBB);
   EntryBuilder.setMBB(*EntryBB);
 

llvm/trunk/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll

 ; RUN: not llc -O0 -global-isel -verify-machineinstrs %s -o - 2>&1 | FileCheck %s --check-prefix=ERROR
 ; RUN: llc -O0 -global-isel -global-isel-abort=0 -verify-machineinstrs %s -o - 2>&1 | FileCheck %s --check-prefix=FALLBACK
 ; RUN: llc -O0 -global-isel -global-isel-abort=2 -pass-remarks-missed='gisel*' -verify-machineinstrs %s -o %t.out 2> %t.err
 ; RUN: FileCheck %s --check-prefix=FALLBACK-WITH-REPORT-OUT < %t.out
 ; RUN: FileCheck %s --check-prefix=FALLBACK-WITH-REPORT-ERR < %t.err
+; RUN: not llc -global-isel -mtriple aarch64_be %s -o - 2>&1 | FileCheck %s --check-prefix=BIG-ENDIAN
 ; This file checks that the fallback path to selection dag works.
 ; The test is fragile in the sense that it must be updated to expose
 ; something that fails with global-isel.
 ; When we cannot produce a test case anymore, that means we can remove
 ; the fallback path.
 
 target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
 target triple = "aarch64--"
 
+; BIG-ENDIAN: unable to translate in big endian mode
+
 ; We use __fixunstfti as the common denominator for __fixunstfti on Linux and
 ; ___fixunstfti on iOS
 ; ERROR: unable to lower arguments: i128 (i128)* (in function: ABIi128)
 ; FALLBACK: ldr q0,
 ; FALLBACK-NEXT: bl __fixunstfti
 ;
 ; FALLBACK-WITH-REPORT-ERR: remark: <unknown>:0:0: unable to lower arguments: i128 (i128)* (in function: ABIi128)
 ; FALLBACK-WITH-REPORT-ERR: warning: Instruction selection used fallback path for ABIi128

llvm/trunk/test/CodeGen/ARM/GlobalISel/arm-irtranslator.ll

 ; RUN: llc -mtriple arm-unknown -mattr=+vfp2,+v4t -global-isel -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=LITTLE
-; RUN: llc -mtriple armeb-unknown -mattr=+vfp2,+v4t -global-isel -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=BIG
+; RUN: llc -mtriple armeb-unknown -mattr=+vfp2,+v4t -global-isel -global-isel-abort=0 -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=BIG
+; XFAIL: armeb
 
 define void @test_void_return() {
 ; CHECK-LABEL: name: test_void_return
 ; CHECK: BX_RET 14, %noreg
 entry:
   ret void
 }
 

llvm/trunk/test/CodeGen/ARM/GlobalISel/arm-param-lowering.ll

 ; RUN: llc -mtriple arm-unknown -mattr=+vfp2,+v4t -global-isel -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=LITTLE
-; RUN: llc -mtriple armeb-unknown -mattr=+vfp2,+v4t -global-isel -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=BIG
+; RUN: llc -mtriple armeb-unknown -mattr=+vfp2,+v4t -global-isel -global-isel-abort=0 -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=BIG
+; XFAIL: armeb
 
 declare arm_aapcscc i32* @simple_reg_params_target(i32, i32*)
 
 define arm_aapcscc i32* @test_call_simple_reg_params(i32 *%a, i32 %b) {
 ; CHECK-LABEL: name: test_call_simple_reg_params
 ; CHECK-DAG: [[AVREG:%[0-9]+]]:_(p0) = COPY %r0
 ; CHECK-DAG: [[BVREG:%[0-9]+]]:_(s32) = COPY %r1
 ; CHECK: ADJCALLSTACKDOWN 0, 0, 14, %noreg, implicit-def %sp, implicit %sp