[llvm] 52b4b35 - Revert "[llvm-exegesis] Set stack pointer register after starting perf counter (#72489)"

[Aiden Grossman via llvm-commits]

Author: Aiden Grossman
Date: 2023-11-29T02:06:13-08:00
New Revision: 52b4b357268ac114f7972e37da1e5954f322df09

URL: https://github.com/llvm/llvm-project/commit/52b4b357268ac114f7972e37da1e5954f322df09
DIFF: https://github.com/llvm/llvm-project/commit/52b4b357268ac114f7972e37da1e5954f322df09.diff

LOG: Revert "[llvm-exegesis] Set stack pointer register after starting perf counter (#72489)"

This reverts commit 9eb80ab3787e1851be8c686651688e870b93506b.

This is causing failures on multiple builders. Pulling it out until I
have time to fix it.

Added: 
    

Modified: 
    llvm/tools/llvm-exegesis/lib/Assembler.cpp

Removed: 
    llvm/test/tools/llvm-exegesis/X86/latency/subprocess-rsp.s


################################################################################
diff  --git a/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-rsp.s b/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-rsp.s
deleted file mode 100644
index 63274c43879951c..000000000000000
--- a/llvm/test/tools/llvm-exegesis/X86/latency/subprocess-rsp.s
+++ /dev/null
@@ -1,18 +0,0 @@
-# REQUIRES: exegesis-can-execute-x86_64
-
-# RUN: llvm-exegesis -mtriple=x86_64-unknown-unknown -mode=latency -snippets-file=%s -execution-mode=subprocess | FileCheck %s
-
-# Check that we can set the value of RSP in subprocess mode without
-# segfaulting as we need to restore it after the rest of the setup is
-# complete to prevent loading from the stack where we set it instead
-# of where the stack actuall is.
-
-# LLVM-EXEGESIS-MEM-DEF test1 4096 2147483647
-# LLVM-EXEGESIS-MEM-MAP test1 1048576
-# LLVM-EXEGESIS-DEFREG RAX 100000
-# LLVM-EXEGESIS-DEFREG R14 100000
-# LLVM-EXEGESIS-DEFREG RSP 100000
-
-movq %r14, (%rax)
-
-# CHECK-NOT: error:           'The benchmarking subprocess sent unexpected signal: Segmentation fault'

diff  --git a/llvm/tools/llvm-exegesis/lib/Assembler.cpp b/llvm/tools/llvm-exegesis/lib/Assembler.cpp
index e17d239faa47e21..e64f4e64ebb4516 100644
--- a/llvm/tools/llvm-exegesis/lib/Assembler.cpp
+++ b/llvm/tools/llvm-exegesis/lib/Assembler.cpp
@@ -19,7 +19,6 @@
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
-#include "llvm/CodeGen/TargetLowering.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/CodeGen/TargetSubtargetInfo.h"
 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
@@ -61,17 +60,7 @@ static bool generateSnippetSetupCode(
     }
     BBF.addInstructions(ET.setStackRegisterToAuxMem());
   }
-  Register StackPointerRegister = BBF.MF.getSubtarget()
-                                      .getTargetLowering()
-                                      ->getStackPointerRegisterToSaveRestore();
   for (const RegisterValue &RV : RegisterInitialValues) {
-    if (GenerateMemoryInstructions) {
-      // If we're generating memory instructions, don't load in the value for
-      // the register with the stack pointer as it will be used later to finish
-      // the setup.
-      if (RV.Register == StackPointerRegister)
-        continue;
-    }
     // Load a constant in the register.
     const auto SetRegisterCode = ET.setRegTo(*MSI, RV.Register, RV.Value);
     if (SetRegisterCode.empty())
@@ -82,18 +71,6 @@ static bool generateSnippetSetupCode(
 #ifdef HAVE_LIBPFM
     BBF.addInstructions(ET.configurePerfCounter(PERF_EVENT_IOC_RESET, true));
 #endif // HAVE_LIBPFM
-    for (const RegisterValue &RV : RegisterInitialValues) {
-      // Load in the stack register now as we're done using it elsewhere
-      // and need to set the value in preparation for executing the
-      // snippet.
-      if (RV.Register == StackPointerRegister)
-        continue;
-      const auto SetRegisterCode = ET.setRegTo(*MSI, RV.Register, RV.Value);
-      if (SetRegisterCode.empty())
-        IsSnippetSetupComplete = false;
-      BBF.addInstructions(SetRegisterCode);
-      break;
-    }
   }
   return IsSnippetSetupComplete;
 }