From 23ad660b5d34930b2b5362f1bba63daee78f6aa4 Mon Sep 17 00:00:00 2001
From: David Sherwood <david.sherwood@arm.com>
Date: Tue, 28 Jul 2020 13:28:14 +0100
Subject: [PATCH] [SVE][CodeGen] At -O0 fallback to DAG ISel when translating
 alloca with scalable types

When building code at -O0 We weren't falling back to DAG ISel correctly
when encountering alloca instructions with scalable vector types. This
is because the alloca has no operands that are scalable. I've fixed this by
adding a check in AArch64ISelLowering::fallBackToDAGISel for alloca
instructions with scalable types.

Differential Revision: https://reviews.llvm.org/D84746
---
 llvm/lib/Target/AArch64/AArch64ISelLowering.cpp        | 5 +++++
 llvm/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll | 8 ++++++++
 2 files changed, 13 insertions(+)

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index f080abd..8b533e9 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -14975,6 +14975,11 @@ bool AArch64TargetLowering::fallBackToDAGISel(const Instruction &Inst) const {
     if (isa<ScalableVectorType>(Inst.getOperand(i)->getType()))
       return true;
 
+  if (const AllocaInst *AI = dyn_cast<AllocaInst>(&Inst)) {
+    if (isa<ScalableVectorType>(AI->getAllocatedType()))
+      return true;
+  }
+
   return false;
 }
 
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll b/llvm/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
index 8ac3e50..f555856 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/arm64-fallback.ll
@@ -244,6 +244,14 @@ define i8 @scalable_call(i8* %addr) #1 {
   ret i8 %res
 }
 
+; FALLBACK-WITH-REPORT-ERR: remark: <unknown>:0:0: unable to translate instruction{{.*}}scalable_alloca
+; FALLBACK-WITH-REPORT-OUT-LABEL: scalable_alloca
+define void @scalable_alloca() #1 {
+  %local0 = alloca <vscale x 16 x i8>
+  load volatile <vscale x 16 x i8>, <vscale x 16 x i8>* %local0
+  ret void
+}
+
 ; FALLBACK-WITH-REPORT-ERR: remark: <unknown>:0:0: unable to translate instruction{{.*}}asm_indirect_output
 ; FALLBACK-WITH-REPORT-OUT-LABEL: asm_indirect_output
 define void @asm_indirect_output() {
-- 
2.7.4