From 8c9a9af652d8b3aa22a8c3ae99793432f13d615e Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Thu, 15 Sep 2016 11:02:19 +0000
Subject: [PATCH] GlobalISel: legalize GEP instructions with small offsets.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281602 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../GlobalISel/MachineLegalizeHelper.cpp      |  7 +++++
 .../AArch64/AArch64MachineLegalizer.cpp       |  6 ++++
 .../AArch64/GlobalISel/legalize-gep.mir       | 31 +++++++++++++++++++
 3 files changed, 44 insertions(+)
 create mode 100644 test/CodeGen/AArch64/GlobalISel/legalize-gep.mir

diff --git a/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp b/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp
index 7c32cd5314b..6d181396079 100644
--- a/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp
+++ b/lib/CodeGen/GlobalISel/MachineLegalizeHelper.cpp
@@ -281,6 +281,13 @@ MachineLegalizeHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx,
     MI.eraseFromParent();
     return Legalized;
   }
+  case TargetOpcode::G_GEP: {
+    assert(TypeIdx == 1 && "unable to legalize pointer of GEP");
+    unsigned OffsetExt = MRI.createGenericVirtualRegister(WideTy);
+    MIRBuilder.buildSExt(OffsetExt, MI.getOperand(2).getReg());
+    MI.getOperand(2).setReg(OffsetExt);
+    return Legalized;
+  }
   }
 }
 
diff --git a/lib/Target/AArch64/AArch64MachineLegalizer.cpp b/lib/Target/AArch64/AArch64MachineLegalizer.cpp
index a5a7ed60ba1..653c7d53e69 100644
--- a/lib/Target/AArch64/AArch64MachineLegalizer.cpp
+++ b/lib/Target/AArch64/AArch64MachineLegalizer.cpp
@@ -43,6 +43,12 @@ AArch64MachineLegalizer::AArch64MachineLegalizer() {
       setAction({BinOp, Ty}, Legal);
   }
 
+  setAction({G_GEP, p0}, Legal);
+  setAction({G_GEP, 1, s64}, Legal);
+
+  for (auto Ty : {s1, s8, s16, s32})
+    setAction({G_GEP, 1, Ty}, WidenScalar);
+
   for (auto BinOp : {G_LSHR, G_ASHR, G_SDIV, G_UDIV}) {
     for (auto Ty : {s32, s64})
       setAction({BinOp, Ty}, Legal);
diff --git a/test/CodeGen/AArch64/GlobalISel/legalize-gep.mir b/test/CodeGen/AArch64/GlobalISel/legalize-gep.mir
new file mode 100644
index 00000000000..4ae441e34d5
--- /dev/null
+++ b/test/CodeGen/AArch64/GlobalISel/legalize-gep.mir
@@ -0,0 +1,31 @@
+# RUN: llc -O0 -run-pass=legalize-mir -global-isel %s -o - 2>&1 | FileCheck %s
+
+--- |
+  target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
+  target triple = "aarch64-apple-ios"
+  define void @test_gep_small() {
+  entry:
+    ret void
+  }
+...
+
+---
+name:            test_gep_small
+registers:
+  - { id: 0, class: _ }
+  - { id: 1, class: _ }
+  - { id: 2, class: _ }
+  - { id: 3, class: _ }
+body: |
+  bb.0.entry:
+    liveins: %x0, %x1, %x2, %x3
+    ; CHECK-LABEL: name: test_gep_small
+    ; CHECK: [[OFFSET_EXT:%[0-9]+]](s64) = G_SEXT %2(s8)
+    ; CHECK: %3(p0) = G_GEP %0, [[OFFSET_EXT]](s64)
+
+    %0(p0) = COPY %x0
+    %1(s64) = COPY %x1
+    %2(s8) = G_TRUNC %1
+    %3(p0) = G_GEP %0, %2(s8)
+    %x0 = COPY %3
+...
-- 
2.50.1