From 7b111890d1f90dcb0e629b07720db1a7ae6f32bf Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Tue, 8 Nov 2016 00:45:29 +0000
Subject: [PATCH] GlobalISel: support selecting G_SELECT on AArch64.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286185 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../AArch64/AArch64InstructionSelector.cpp    | 40 +++++++++++++++++
 .../GlobalISel/arm64-instructionselect.mir    | 44 +++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/lib/Target/AArch64/AArch64InstructionSelector.cpp b/lib/Target/AArch64/AArch64InstructionSelector.cpp
index 7f2ce779a0cb3..80ea8d6d61d40 100644
--- a/lib/Target/AArch64/AArch64InstructionSelector.cpp
+++ b/lib/Target/AArch64/AArch64InstructionSelector.cpp
@@ -18,6 +18,7 @@
 #include "AArch64RegisterInfo.h"
 #include "AArch64Subtarget.h"
 #include "AArch64TargetMachine.h"
+#include "MCTargetDesc/AArch64AddressingModes.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstr.h"
@@ -952,6 +953,45 @@ bool AArch64InstructionSelector::select(MachineInstr &I) const {
   case TargetOpcode::G_BITCAST:
     return selectCopy(I, TII, MRI, TRI, RBI);
 
+  case TargetOpcode::G_SELECT: {
+    if (MRI.getType(I.getOperand(1).getReg()) != LLT::scalar(1)) {
+      DEBUG(dbgs() << "G_SELECT cond has type: " << Ty
+                   << ", expected: " << LLT::scalar(1) << '\n');
+      return false;
+    }
+
+    const unsigned CondReg = I.getOperand(1).getReg();
+    const unsigned TReg = I.getOperand(2).getReg();
+    const unsigned FReg = I.getOperand(3).getReg();
+
+    unsigned CSelOpc = 0;
+
+    if (Ty == LLT::scalar(32)) {
+      CSelOpc = AArch64::CSELWr;
+    } else if (Ty == LLT::scalar(64)) {
+      CSelOpc = AArch64::CSELXr;
+    } else {
+      return false;
+    }
+
+    MachineInstr &TstMI =
+        *BuildMI(MBB, I, I.getDebugLoc(), TII.get(AArch64::ANDSWri))
+             .addDef(AArch64::WZR)
+             .addUse(CondReg)
+             .addImm(AArch64_AM::encodeLogicalImmediate(1, 32));
+
+    MachineInstr &CSelMI = *BuildMI(MBB, I, I.getDebugLoc(), TII.get(CSelOpc))
+                                .addDef(I.getOperand(0).getReg())
+                                .addUse(TReg)
+                                .addUse(FReg)
+                                .addImm(AArch64CC::NE);
+
+    constrainSelectedInstRegOperands(TstMI, TII, TRI, RBI);
+    constrainSelectedInstRegOperands(CSelMI, TII, TRI, RBI);
+
+    I.eraseFromParent();
+    return true;
+  }
   case TargetOpcode::G_ICMP: {
     if (Ty != LLT::scalar(1)) {
       DEBUG(dbgs() << "G_ICMP result has type: " << Ty
diff --git a/test/CodeGen/AArch64/GlobalISel/arm64-instructionselect.mir b/test/CodeGen/AArch64/GlobalISel/arm64-instructionselect.mir
index 7d0ec021239c8..e9c165b892be6 100644
--- a/test/CodeGen/AArch64/GlobalISel/arm64-instructionselect.mir
+++ b/test/CodeGen/AArch64/GlobalISel/arm64-instructionselect.mir
@@ -150,6 +150,7 @@
 
   define void @phi() { ret void }
 
+  define void @select() { ret void }
 ...
 
 ---
@@ -2874,3 +2875,46 @@ body:             |
     %s0 = COPY %2
     RET_ReallyLR implicit %s0
 ...
+
+---
+# CHECK-LABEL: name: select
+name:            select
+legalized:       true
+regBankSelected: true
+tracksRegLiveness: true
+
+# CHECK:      registers:
+# CHECK-NEXT:  - { id: 0, class: gpr32 }
+# CHECK-NEXT:  - { id: 1, class: gpr32 }
+# CHECK-NEXT:  - { id: 2, class: gpr32 }
+# CHECK-NEXT:  - { id: 3, class: gpr32 }
+# CHECK-NEXT:  - { id: 4, class: gpr64 }
+# CHECK-NEXT:  - { id: 5, class: gpr64 }
+# CHECK-NEXT:  - { id: 6, class: gpr64 }
+registers:
+  - { id: 0, class: gpr }
+  - { id: 1, class: gpr }
+  - { id: 2, class: gpr }
+  - { id: 3, class: gpr }
+  - { id: 4, class: gpr }
+  - { id: 5, class: gpr }
+  - { id: 6, class: gpr }
+
+# CHECK:  body:
+# CHECK:      %wzr = ANDSWri %0, 0, implicit-def %nzcv
+# CHECK:      %3 = CSELWr %1, %2, 1, implicit %nzcv
+# CHECK:      %wzr = ANDSWri %0, 0, implicit-def %nzcv
+# CHECK:      %6 = CSELXr %4, %5, 1, implicit %nzcv
+body:             |
+  bb.0:
+    liveins: %w0, %w1, %w2
+    %0(s1) = COPY %w0
+
+    %1(s32) = COPY %w1
+    %2(s32) = COPY %w2
+    %3(s32) = G_SELECT %0, %1, %2
+
+    %4(s64) = COPY %x0
+    %5(s64) = COPY %x1
+    %6(s64) = G_SELECT %0, %4, %5
+...