[llvm] 8bb6c8a - [AMDGPU] Fix data race on RegisterBank initialization.

[Huihui Zhang via llvm-commits]

Author: Huihui Zhang
Date: 2020-01-29T10:14:40-08:00
New Revision: 8bb6c8a22af845618cfd6c27853dca1b48d30ce0

URL: https://github.com/llvm/llvm-project/commit/8bb6c8a22af845618cfd6c27853dca1b48d30ce0
DIFF: https://github.com/llvm/llvm-project/commit/8bb6c8a22af845618cfd6c27853dca1b48d30ce0.diff

LOG: [AMDGPU] Fix data race on RegisterBank initialization.

Summary:
The initialization of RegisterBank needs to be done only once. The
logic of AlreadyInit has data race, use llvm::call_once instead.

This is continuing work of D73587.

Reviewers: arsenm, tstellar, ronlieb, efriedma, apazos, nhaehnle

Reviewed By: nhaehnle

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73604

Added: 
    

Modified: 
    llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
index 476ab798d004..3007d7eead86 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
@@ -197,15 +197,15 @@ AMDGPURegisterBankInfo::AMDGPURegisterBankInfo(const GCNSubtarget &ST)
       TII(Subtarget.getInstrInfo()) {
 
   // HACK: Until this is fully tablegen'd.
-  static bool AlreadyInit = false;
-  if (AlreadyInit)
-    return;
+  static llvm::once_flag InitializeRegisterBankFlag;
 
-  AlreadyInit = true;
+  static auto InitializeRegisterBankOnce = [this]() {
+    assert(&getRegBank(AMDGPU::SGPRRegBankID) == &AMDGPU::SGPRRegBank &&
+           &getRegBank(AMDGPU::VGPRRegBankID) == &AMDGPU::VGPRRegBank &&
+           &getRegBank(AMDGPU::AGPRRegBankID) == &AMDGPU::AGPRRegBank);
+  };
 
-  assert(&getRegBank(AMDGPU::SGPRRegBankID) == &AMDGPU::SGPRRegBank &&
-         &getRegBank(AMDGPU::VGPRRegBankID) == &AMDGPU::VGPRRegBank &&
-         &getRegBank(AMDGPU::AGPRRegBankID) == &AMDGPU::AGPRRegBank);
+  llvm::call_once(InitializeRegisterBankFlag, InitializeRegisterBankOnce);
 }
 
 static bool isVectorRegisterBank(const RegisterBank &Bank) {