From 50d53886ed865fe2e45d0d7ec0617faada2ffe20 Mon Sep 17 00:00:00 2001
From: Ng Zhi An <zhin@chromium.org>
Date: Tue, 21 Apr 2020 11:27:48 -0700
Subject: [PATCH] [arm] Remove static Bit helpers on Instr

These are almost unused, except for 1 case of Bit, which is probably
incorrect. These static helpers can cause subtle error, e.g.
instr->Bit(1, 3) does not get you bits 1 to 3, but rather calls the
static method Bit(Instr, int).

An example of this bug was fixed in https://crrev.com/c/2157799.

Change-Id: I98c4464c4315af48b9d36472ffd6f16aa74aa18b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2158824
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67315}
---
 src/codegen/arm/constants-arm.h    | 17 -----------------
 src/execution/arm/simulator-arm.cc |  2 +-
 2 files changed, 1 insertion(+), 18 deletions(-)

diff --git a/src/codegen/arm/constants-arm.h b/src/codegen/arm/constants-arm.h
index 171de9e1d7..a7726a8f25 100644
--- a/src/codegen/arm/constants-arm.h
+++ b/src/codegen/arm/constants-arm.h
@@ -459,23 +459,6 @@ class Instruction {
     return InstructionBits() & (((2 << (hi - lo)) - 1) << lo);
   }
 
-  // Static support.
-
-  // Extract a single bit from the instruction bits and return it as bit 0 in
-  // the result.
-  static inline int Bit(Instr instr, int nr) { return (instr >> nr) & 1; }
-
-  // Extract a bit field <hi:lo> from the instruction bits and return it in the
-  // least-significant bits of the result.
-  static inline int Bits(Instr instr, int hi, int lo) {
-    return (instr >> lo) & ((2 << (hi - lo)) - 1);
-  }
-
-  // Read a bit field <hi:lo>, leaving its position unchanged in the result.
-  static inline int BitField(Instr instr, int hi, int lo) {
-    return instr & (((2 << (hi - lo)) - 1) << lo);
-  }
-
   // Accessors for the different named fields used in the ARM encoding.
   // The naming of these accessor corresponds to figure A3-1.
   //
diff --git a/src/execution/arm/simulator-arm.cc b/src/execution/arm/simulator-arm.cc
index 4aac7dc960..019542b12d 100644
--- a/src/execution/arm/simulator-arm.cc
+++ b/src/execution/arm/simulator-arm.cc
@@ -4589,7 +4589,7 @@ void Simulator::DecodeSpecialCondition(Instruction* instr) {
           case 0: {
             // vmov.i32 Qd, #<imm>
             int vd = instr->VFPDRegValue(kSimd128Precision);
-            uint64_t imm = instr->Bit(24, 24) << 7;  // i
+            uint64_t imm = instr->Bit(24) << 7;      // i
             imm |= instr->Bits(18, 16) << 4;         // imm3
             imm |= instr->Bits(3, 0);                // imm4
             imm |= imm << 32;