[GlobalISel] Bail out early for big-endian (#103310)

If we continue through the function we can currently hit crashes. We can
bail out early and fall back to SDAG.

Fixes #103032

(cherry picked from commit 05d17a1)

Author: davemgreen

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -3889,6 +3889,7 @@ bool IRTranslator::runOnMachineFunction(MachineFunction &CurMF) {
                                F.getSubprogram(), &F.getEntryBlock());
     R << "unable to translate in big endian mode";
     reportTranslationError(*MF, *TPC, *ORE, R);
+    return false;
   }
 
   // Release the per-function state when we return, whether we succeeded or not.

llvm/lib/Target/ARM/ARMCallLowering.cpp

@@ -50,6 +50,13 @@
 
 using namespace llvm;
 
+// Whether Big-endian GISel is enabled, defaults to off, can be enabled for
+// testing.
+static cl::opt<bool>
+    EnableGISelBigEndian("enable-arm-gisel-bigendian", cl::Hidden,
+                         cl::init(false),
+                         cl::desc("Enable Global-ISel Big Endian Lowering"));
+
 ARMCallLowering::ARMCallLowering(const ARMTargetLowering &TLI)
     : CallLowering(&TLI) {}
 
@@ -539,3 +546,5 @@ bool ARMCallLowering::lowerCall(MachineIRBuilder &MIRBuilder, CallLoweringInfo &
 
   return true;
 }
+
+bool ARMCallLowering::enableBigEndian() const { return EnableGISelBigEndian; }

llvm/lib/Target/ARM/ARMCallLowering.h

@@ -42,6 +42,8 @@ class ARMCallLowering : public CallLowering {
   bool lowerCall(MachineIRBuilder &MIRBuilder,
                  CallLoweringInfo &Info) const override;
 
+  bool enableBigEndian() const override;
+
 private:
   bool lowerReturnVal(MachineIRBuilder &MIRBuilder, const Value *Val,
                       ArrayRef<Register> VRegs,

llvm/test/CodeGen/AArch64/GlobalISel/endian_fallback.ll

@@ -0,0 +1,21 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc -mtriple aarch64-unknown-linux-musl -O0 -global-isel-abort=2 < %s 2>&1 | FileCheck %s --check-prefix=CHECK-LE
+; RUN: llc -mtriple aarch64_be-unknown-linux-musl -O0 -global-isel-abort=2 < %s 2>&1 | FileCheck %s --check-prefix=CHECK-BE
+
+; Make sure we fall-back to SDAG for BE targets.
+
+; CHECK-LE-NOT: warning: Instruction selection used fallback path for foo
+; CHECK-BE: warning: Instruction selection used fallback path for foo
+
+define <4 x i6> @foo(float %0, <4 x i6> %1) {
+; CHECK-LE-LABEL: foo:
+; CHECK-LE:       // %bb.0:
+; CHECK-LE-NEXT:    fmov d0, d1
+; CHECK-LE-NEXT:    ret
+;
+; CHECK-BE-LABEL: foo:
+; CHECK-BE:       // %bb.0:
+; CHECK-BE-NEXT:    fmov d0, d1
+; CHECK-BE-NEXT:    ret
+  ret <4 x i6> %1
+}

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

@@ -1,5 +1,5 @@
 ; 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 -global-isel-abort=0 -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 -enable-arm-gisel-bigendian -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=BIG
 
 define void @test_void_return() {
 ; CHECK-LABEL: name: test_void_return

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

@@ -1,5 +1,5 @@
 ; RUN: llc -O0 -mtriple arm-unknown -mattr=+vfp2,+v4t -global-isel -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=ARM -check-prefix=LITTLE
-; RUN: llc -O0 -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=ARM -check-prefix=BIG
+; RUN: llc -O0 -mtriple armeb-unknown -mattr=+vfp2,+v4t -global-isel -global-isel-abort=0 -enable-arm-gisel-bigendian -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=ARM -check-prefix=BIG
 ; RUN: llc -O0 -mtriple thumb-unknown -mattr=+vfp2,+v6t2 -global-isel -stop-after=irtranslator -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=CHECK -check-prefix=LITTLE -check-prefix=THUMB
 
 declare arm_aapcscc ptr @simple_reg_params_target(i32, ptr)