From 3cec2c1d642e360308196bae0f2a719a86fac309 Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar@redhat.com>
Date: Tue, 17 Apr 2018 20:17:43 +0000
Subject: Merging r329761:

------------------------------------------------------------------------
r329761 | gberry | 2018-04-10 14:43:03 -0700 (Tue, 10 Apr 2018) | 13 lines

[AArch64][Falkor] Fix bug in Falkor HWPF collision avoidance pass.

Summary:
When inserting MOVs to avoid Falkor HWPF collisions, the non-base
register operand of load instructions (e.g. a register offset) was not
being considered live, so it could potentially have been used as a
scratch register, clobbering the actual offset value.

Reviewers: mcrosier

Subscribers: rengolin, javed.absar, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D45502
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llvm-svn: 330209
---
 llvm/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp | 18 +++++++++++++++++
 llvm/test/CodeGen/AArch64/falkor-hwpf-fix.mir    | 25 ++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/llvm/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp b/llvm/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp
index d1ddb2e3ef70..0d00dab598d5 100644
--- a/llvm/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FalkorHWPFFix.cpp
@@ -46,6 +46,7 @@
 #include "llvm/Pass.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/DebugCounter.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 #include <iterator>
@@ -60,6 +61,8 @@ STATISTIC(NumCollisionsAvoided,
           "Number of HW prefetch tag collisions avoided");
 STATISTIC(NumCollisionsNotAvoided,
           "Number of HW prefetch tag collisions not avoided due to lack of regsiters");
+DEBUG_COUNTER(FixCounter, "falkor-hwpf",
+              "Controls which tag collisions are avoided");
 
 namespace {
 
@@ -729,6 +732,21 @@ void FalkorHWPFFix::runOnLoop(MachineLoop &L, MachineFunction &Fn) {
       bool Fixed = false;
       DEBUG(dbgs() << "Attempting to fix tag collision: " << MI);
 
+      if (!DebugCounter::shouldExecute(FixCounter)) {
+        DEBUG(dbgs() << "Skipping fix due to debug counter:\n  " << MI);
+        continue;
+      }
+
+      // Add the non-base registers of MI as live so we don't use them as
+      // scratch registers.
+      for (unsigned OpI = 0, OpE = MI.getNumOperands(); OpI < OpE; ++OpI) {
+        if (OpI == static_cast<unsigned>(LdI.BaseRegIdx))
+          continue;
+        MachineOperand &MO = MI.getOperand(OpI);
+        if (MO.isReg() && MO.readsReg())
+          LR.addReg(MO.getReg());
+      }
+
       for (unsigned ScratchReg : AArch64::GPR64RegClass) {
         if (!LR.available(ScratchReg) || MRI.isReserved(ScratchReg))
           continue;
diff --git a/llvm/test/CodeGen/AArch64/falkor-hwpf-fix.mir b/llvm/test/CodeGen/AArch64/falkor-hwpf-fix.mir
index 38622ae0e49a..28b19f877685 100644
--- a/llvm/test/CodeGen/AArch64/falkor-hwpf-fix.mir
+++ b/llvm/test/CodeGen/AArch64/falkor-hwpf-fix.mir
@@ -353,3 +353,28 @@ body: |
   bb.1:
     RET_ReallyLR
 ...
+---
+# Check that non-base registers are considered live when finding a
+# scratch register by making sure we don't use %x2 for the scratch
+# register for the inserted ORRXrs.
+# CHECK-LABEL: name: hwpf_offreg
+# CHECK: %x3 = ORRXrs %xzr, %x1, 0
+# CHECK: %w10 = LDRWroX %x3, %x2, 0, 0
+name:            hwpf_offreg
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: %w0, %x1, %x2, %x17, %x18
+
+    %w10 = LDRWroX %x1, %x2, 0, 0 :: ("aarch64-strided-access" load 4)
+
+    %x2 = ORRXrs %xzr, %x10, 0
+    %w26 = LDRWroX %x1, %x2, 0, 0
+
+    %w0 = SUBWri %w0, 1, 0
+    %wzr = SUBSWri %w0, 0, 0, implicit-def %nzcv
+    Bcc 9, %bb.0, implicit %nzcv
+
+  bb.1:
+    RET_ReallyLR
+...
-- 
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