[AArch64][GlobalISel] Fallback if the +strict-align target feature is given.

aemerson · aemerson · commit 765b37abdfc0 · 2020-01-23T14:45:29.000-08:00
Works around PR44246.
diff --git a/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -1423,6 +1423,14 @@ bool AArch64InstructionSelector::select(MachineInstr &I) {
   MachineFunction &MF = *MBB.getParent();
   MachineRegisterInfo &MRI = MF.getRegInfo();
 
+  const AArch64Subtarget *Subtarget =
+      &static_cast<const AArch64Subtarget &>(MF.getSubtarget());
+  if (Subtarget->requiresStrictAlign()) {
+    // We don't support this feature yet.
+    LLVM_DEBUG(dbgs() << "AArch64 GISel does not support strict-align yet\n");
+    return false;
+  }
+
   unsigned Opcode = I.getOpcode();
   // G_PHI requires same handling as PHI
   if (!isPreISelGenericOpcode(Opcode) || Opcode == TargetOpcode::G_PHI) {
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll b/llvm/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
@@ -209,3 +209,12 @@ define <4 x i16> @zext_v4s8(<4 x i8> %in) {
   ret <4 x i16> %ext
 }
 
+; FALLBACK-WITH-REPORT-ERR: remark: <unknown>:0:0: cannot select: RET_ReallyLR implicit $x0 (in function: strict_align_feature)
+; FALLBACK-WITH-REPORT-ERR: warning: Instruction selection used fallback path for strict_align_feature
+; FALLBACK-WITH-REPORT-OUT-LABEL: strict_align_feature
+define i64 @strict_align_feature(i64* %p) #0 {
+  %x = load i64, i64* %p, align 1
+  ret i64 %x
+}
+
+attributes #0 = { "target-features"="+strict-align" }
