From e1f835ab596a984f5d055ca98db375b72ddd7f14 Mon Sep 17 00:00:00 2001
From: Ahmed Bougacha <ahmed.bougacha@gmail.com>
Date: Tue, 28 Apr 2015 01:37:11 +0000
Subject: [PATCH] [MC] Use LShr for constant evaluation of ">>" on
 ELF/arm64--darwin.

This matches other assemblers and is less unexpected (e.g. PR23227).
On ELF, I tried binutils gas v2.24 and nasm 2.10.09, and they both
agree on LShr.  On COFF, I couldn't get my hands on an assembler yet,
so don't change the behavior.  For now, don't change it on non-AArch64
Darwin either, as the other assembler is gas v1.38, which does an AShr.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235963 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/MC/MCAsmInfo.cpp                                |  2 +-
 lib/MC/MCAsmInfoCOFF.cpp                            |  4 ++++
 lib/MC/MCAsmInfoDarwin.cpp                          |  5 +++++
 .../AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp       |  4 ++++
 test/MC/AArch64/expr-shr.s                          |  8 ++++++++
 test/MC/ARM/bracket-exprs.s                         |  2 +-
 test/MC/AsmParser/expr-shr.s                        | 13 +++++++++++++
 test/MC/ELF/bracket-exprs.s                         |  2 +-
 8 files changed, 37 insertions(+), 3 deletions(-)
 create mode 100644 test/MC/AArch64/expr-shr.s
 create mode 100644 test/MC/AsmParser/expr-shr.s

diff --git a/lib/MC/MCAsmInfo.cpp b/lib/MC/MCAsmInfo.cpp
index 22de8bd13dc..1a45b5a389f 100644
--- a/lib/MC/MCAsmInfo.cpp
+++ b/lib/MC/MCAsmInfo.cpp
@@ -90,7 +90,7 @@ MCAsmInfo::MCAsmInfo() {
   DwarfRegNumForCFI = false;
   NeedsDwarfSectionOffsetDirective = false;
   UseParensForSymbolVariant = false;
-  UseLogicalShr = false;
+  UseLogicalShr = true;
 
   // FIXME: Clang's logic should be synced with the logic used to initialize
   //        this member and the two implementations should be merged.
diff --git a/lib/MC/MCAsmInfoCOFF.cpp b/lib/MC/MCAsmInfoCOFF.cpp
index bb3f0d3a429..97fc76a9adb 100644
--- a/lib/MC/MCAsmInfoCOFF.cpp
+++ b/lib/MC/MCAsmInfoCOFF.cpp
@@ -36,6 +36,10 @@ MCAsmInfoCOFF::MCAsmInfoCOFF() {
   NeedsDwarfSectionOffsetDirective = true;
 
   UseIntegratedAssembler = true;
+
+  // FIXME: For now keep the previous behavior, AShr. Need to double-check
+  // other COFF-targeting assemblers and change this if necessary.
+  UseLogicalShr = false;
 }
 
 void MCAsmInfoMicrosoft::anchor() { }
diff --git a/lib/MC/MCAsmInfoDarwin.cpp b/lib/MC/MCAsmInfoDarwin.cpp
index ae9486d3db4..bb90ff2c350 100644
--- a/lib/MC/MCAsmInfoDarwin.cpp
+++ b/lib/MC/MCAsmInfoDarwin.cpp
@@ -93,4 +93,9 @@ MCAsmInfoDarwin::MCAsmInfoDarwin() {
 
   UseIntegratedAssembler = true;
   SetDirectiveSuppressesReloc = true;
+
+  // FIXME: For now keep the previous behavior, AShr, matching the previous
+  // behavior of as(1) (both -q and -Q: resp. LLVM and gas v1.38).
+  // If/when this changes, the AArch64 Darwin special case can go away.
+  UseLogicalShr = false;
 }
diff --git a/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp b/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp
index f048474fd4a..c4122040041 100644
--- a/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp
+++ b/lib/Target/AArch64/MCTargetDesc/AArch64MCAsmInfo.cpp
@@ -48,6 +48,10 @@ AArch64MCAsmInfoDarwin::AArch64MCAsmInfoDarwin() {
   UseDataRegionDirectives = true;
 
   ExceptionsType = ExceptionHandling::DwarfCFI;
+
+  // AArch64 Darwin doesn't have the baggage of X86/ARM, so it's fine to use
+  // LShr instead of AShr.
+  UseLogicalShr = true;
 }
 
 const MCExpr *AArch64MCAsmInfoDarwin::getExprForPersonalitySymbol(
diff --git a/test/MC/AArch64/expr-shr.s b/test/MC/AArch64/expr-shr.s
new file mode 100644
index 00000000000..aa23878e5ad
--- /dev/null
+++ b/test/MC/AArch64/expr-shr.s
@@ -0,0 +1,8 @@
+// RUN: llvm-mc -triple aarch64-unknown-unknown-elf %s | FileCheck %s --check-prefix=ELF
+// RUN: llvm-mc -triple aarch64-unknown-darwin %s | FileCheck %s --check-prefix=DARWIN
+
+.data
+
+// ELF: .xword 3
+// DARWIN: .quad 3
+.quad (~0 >> 62)
diff --git a/test/MC/ARM/bracket-exprs.s b/test/MC/ARM/bracket-exprs.s
index 922bf703701..74f3323cd2d 100644
--- a/test/MC/ARM/bracket-exprs.s
+++ b/test/MC/ARM/bracket-exprs.s
@@ -1,7 +1,7 @@
 // RUN: llvm-mc -triple arm-unknown-linux %s | FileCheck %s
 
 // CHECK: .byte 1
-.if [~0 >> 1] == -1
+.if [~0 >> 63] == 1
 .byte 1
 .else
 .byte 2
diff --git a/test/MC/AsmParser/expr-shr.s b/test/MC/AsmParser/expr-shr.s
new file mode 100644
index 00000000000..fc117b64e95
--- /dev/null
+++ b/test/MC/AsmParser/expr-shr.s
@@ -0,0 +1,13 @@
+// RUN: llvm-mc -triple x86_64-unknown-unknown-elf %s | FileCheck %s --check-prefix=CHECK
+// RUN: llvm-mc -triple x86_64-pc-windows-msvc %s | FileCheck %s --check-prefix=MSVC
+// RUN: llvm-mc -triple x86_64-unknown-darwin %s | FileCheck %s --check-prefix=DARWIN
+
+.data
+
+// CHECK: .quad 3
+
+// Both COFF and Darwin still use AShr.
+// MSVC: .quad -1
+// DARWIN: .quad -1
+
+.quad (~0 >> 62)
diff --git a/test/MC/ELF/bracket-exprs.s b/test/MC/ELF/bracket-exprs.s
index 96f9f9aa450..e7299fde700 100644
--- a/test/MC/ELF/bracket-exprs.s
+++ b/test/MC/ELF/bracket-exprs.s
@@ -1,7 +1,7 @@
 // RUN: llvm-mc -triple i386-unknown-unknown %s | FileCheck %s
 
 // CHECK: .byte 1
-.if [~0 >> 1] == -1
+.if [~0 >> 63] == 1
 .byte 1
 .else
 .byte 2