From 905c589291a16bf29189507e0ff468e0eb0f97b0 Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@hanshq.net>
Date: Fri, 24 Aug 2018 22:46:33 +0000
Subject: [PATCH] Revert r323281 "Adjust MaxAtomicInlineWidth for i386/i486
 targets."

As reported on http://lists.llvm.org/pipermail/cfe-dev/2018-August/058760.html,
this broke i386-freebsd11 due to its lack of atomic 64 bit primitives.

While that's not really this commit's fault, let's revert back to the old
behaviour until this can be fixed. This means generating cmpxchg8b etc for i386
and i486 which don't technically support those, but that's been the behaviour
for a long time, so a little longer probably doesn't hurt that much.

> Adjust MaxAtomicInlineWidth for i386/i486 targets.
>
> This is to fix the bug reported in https://bugs.llvm.org/show_bug.cgi?id=34347#c6.
> Currently, all  MaxAtomicInlineWidth of x86-32 targets are set to 64. However,
> i386 doesn't support any cmpxchg related instructions. i486 only supports cmpxchg.
> So in this patch MaxAtomicInlineWidth is reset as follows:
> For i386, the MaxAtomicInlineWidth should be 0 because no cmpxchg is supported.
> For i486, the MaxAtomicInlineWidth should be 32 because it supports cmpxchg.
> For others 32 bits x86 cpu, the MaxAtomicInlineWidth should be 64 because of cmpxchg8b.
>
> Differential Revision: https://reviews.llvm.org/D42154

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@340666 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Basic/Targets/X86.h           |  8 ++--
 test/CodeGenCXX/atomic-inline.cpp | 61 +------------------------------
 2 files changed, 5 insertions(+), 64 deletions(-)

diff --git a/lib/Basic/Targets/X86.h b/lib/Basic/Targets/X86.h
index 077b590943..a77757af67 100644
--- a/lib/Basic/Targets/X86.h
+++ b/lib/Basic/Targets/X86.h
@@ -349,11 +349,9 @@ public:
          (1 << TargetInfo::LongDouble));
 
     // x86-32 has atomics up to 8 bytes
-    CPUKind Kind = getCPUKind(Opts.CPU);
-    if (Kind >= CK_i586 || Kind == CK_Generic)
-      MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
-    else if (Kind >= CK_i486)
-      MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 32;
+    // FIXME: Check that we actually have cmpxchg8b before setting
+    // MaxAtomicInlineWidth. (cmpxchg8b is an i586 instruction.)
+    MaxAtomicPromoteWidth = MaxAtomicInlineWidth = 64;
   }
 
   BuiltinVaListKind getBuiltinVaListKind() const override {
diff --git a/test/CodeGenCXX/atomic-inline.cpp b/test/CodeGenCXX/atomic-inline.cpp
index 327f85d566..fe727589d2 100644
--- a/test/CodeGenCXX/atomic-inline.cpp
+++ b/test/CodeGenCXX/atomic-inline.cpp
@@ -1,52 +1,6 @@
 // RUN: %clang_cc1 %s -std=c++11 -emit-llvm -o - -triple=x86_64-linux-gnu | FileCheck %s
 // RUN: %clang_cc1 %s -std=c++11 -emit-llvm -o - -triple=x86_64-linux-gnu -target-cpu core2 | FileCheck %s --check-prefix=CORE2
-// RUN: %clang_cc1 %s -std=c++11 -emit-llvm -o - -triple=i386-linux-gnu -target-cpu i386 | FileCheck %s --check-prefix=I386
-// RUN: %clang_cc1 %s -std=c++11 -emit-llvm -o - -triple=i386-linux-gnu -target-cpu i486 | FileCheck %s --check-prefix=I486
-// Check the atomic code generation for cpu targets w/wo cx, cx8 and cx16 support.
-
-struct alignas(4) AM4 {
-  short f1, f2;
-};
-AM4 m4;
-AM4 load4() {
-  AM4 am;
-  // CHECK-LABEL: @_Z5load4v
-  // CHECK: load atomic i32, {{.*}} monotonic
-  // CORE2-LABEL: @_Z5load4v
-  // CORE2: load atomic i32, {{.*}} monotonic
-  // I386-LABEL: @_Z5load4v
-  // I386: call i32 @__atomic_load_4
-  // I486-LABEL: @_Z5load4v
-  // I486: load atomic i32, {{.*}} monotonic
-  __atomic_load(&m4, &am, 0);
-  return am;
-}
-
-AM4 s4;
-void store4() {
-  // CHECK-LABEL: @_Z6store4v
-  // CHECK: store atomic i32 {{.*}} monotonic
-  // CORE2-LABEL: @_Z6store4v
-  // CORE2: store atomic i32 {{.*}} monotonic
-  // I386-LABEL: @_Z6store4v
-  // I386: call void @__atomic_store_4
-  // I486-LABEL: @_Z6store4v
-  // I486: store atomic i32 {{.*}} monotonic
-  __atomic_store(&m4, &s4, 0);
-}
-
-bool cmpxchg4() {
-  AM4 am;
-  // CHECK-LABEL: @_Z8cmpxchg4v
-  // CHECK: cmpxchg i32* {{.*}} monotonic
-  // CORE2-LABEL: @_Z8cmpxchg4v
-  // CORE2: cmpxchg i32* {{.*}} monotonic
-  // I386-LABEL: @_Z8cmpxchg4v
-  // I386: call zeroext i1 @__atomic_compare_exchange_4
-  // I486-LABEL: @_Z8cmpxchg4v
-  // I486: cmpxchg i32* {{.*}} monotonic
-  return __atomic_compare_exchange(&m4, &s4, &am, 0, 0, 0);
-}
+// Check the atomic code generation for cpu targets w/wo cx16 support.
 
 struct alignas(8) AM8 {
   int f1, f2;
@@ -58,10 +12,6 @@ AM8 load8() {
   // CHECK: load atomic i64, {{.*}} monotonic
   // CORE2-LABEL: @_Z5load8v
   // CORE2: load atomic i64, {{.*}} monotonic
-  // I386-LABEL: @_Z5load8v
-  // I386: call i64 @__atomic_load_8
-  // I486-LABEL: @_Z5load8v
-  // I486: call i64 @__atomic_load_8
   __atomic_load(&m8, &am, 0);
   return am;
 }
@@ -72,10 +22,6 @@ void store8() {
   // CHECK: store atomic i64 {{.*}} monotonic
   // CORE2-LABEL: @_Z6store8v
   // CORE2: store atomic i64 {{.*}} monotonic
-  // I386-LABEL: @_Z6store8v
-  // I386: call void @__atomic_store_8
-  // I486-LABEL: @_Z6store8v
-  // I486: call void @__atomic_store_8
   __atomic_store(&m8, &s8, 0);
 }
 
@@ -85,10 +31,6 @@ bool cmpxchg8() {
   // CHECK: cmpxchg i64* {{.*}} monotonic
   // CORE2-LABEL: @_Z8cmpxchg8v
   // CORE2: cmpxchg i64* {{.*}} monotonic
-  // I386-LABEL: @_Z8cmpxchg8v
-  // I386: call zeroext i1 @__atomic_compare_exchange_8
-  // I486-LABEL: @_Z8cmpxchg8v
-  // I486: call zeroext i1 @__atomic_compare_exchange_8
   return __atomic_compare_exchange(&m8, &s8, &am, 0, 0, 0);
 }
 
@@ -124,3 +66,4 @@ bool cmpxchg16() {
   // CORE2: cmpxchg i128* {{.*}} monotonic
   return __atomic_compare_exchange(&m16, &s16, &am, 0, 0, 0);
 }
+
-- 
2.40.0