[X86] Remove X86RegisterInfo::getSEHRegNum.

[topperc]

As far as I can tell, there's no way to call this. There are no calls in the X86 directory. It has the same name as a function in MCRegisterInfo, but that function takes a MCRegister and isn't virtual.

The function in MCRegisterInfo uses a DenseMap populated by X86_MC::initLLVMToSEHAndCVRegMapping. The DenseMap is populated for every physical register using the encoding value. I think that means the function in MCRegisterInfo would return the same value as the function in X86RegisterInfo.

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: Craig Topper (topperc)

Changes

As far as I can tell, there's no way to call this. There are no calls in the X86 directory. It has the same name as a function in MCRegisterInfo, but that function takes a MCRegister and isn't virtual.

The function in MCRegisterInfo uses a DenseMap populated by X86_MC::initLLVMToSEHAndCVRegMapping. The DenseMap is populated for every physical register using the encoding value. I think that means the function in MCRegisterInfo would return the same value as the function in X86RegisterInfo.

---

Full diff: https://github.com/llvm/llvm-project/pull/106866.diff

2 Files Affected:

• (modified) llvm/lib/Target/X86/X86RegisterInfo.cpp (-5)
• (modified) llvm/lib/Target/X86/X86RegisterInfo.h (-3)

diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 638eb1c4f11e41..1d8808f4e2b7d0 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -83,11 +83,6 @@ X86RegisterInfo::X86RegisterInfo(const Triple &TT)
   }
 }
 
-int
-X86RegisterInfo::getSEHRegNum(unsigned i) const {
-  return getEncodingValue(i);
-}
-
 const TargetRegisterClass *
 X86RegisterInfo::getSubClassWithSubReg(const TargetRegisterClass *RC,
                                        unsigned Idx) const {
diff --git a/llvm/lib/Target/X86/X86RegisterInfo.h b/llvm/lib/Target/X86/X86RegisterInfo.h
index 7296a5f021e4ad..2f73698a4b94d3 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.h
+++ b/llvm/lib/Target/X86/X86RegisterInfo.h
@@ -54,9 +54,6 @@ class X86RegisterInfo final : public X86GenRegisterInfo {
   /// Return the number of registers for the function.
   unsigned getNumSupportedRegs(const MachineFunction &MF) const override;
 
-  // FIXME: This should be tablegen'd like getDwarfRegNum is
-  int getSEHRegNum(unsigned i) const;
-
   /// getMatchingSuperRegClass - Return a subclass of the specified register
   /// class A so that each register in it has a sub-register of the
   /// specified sub-register index which is in the specified register class B.

[phoebewang]

The ARM/AArch64 definition also look redundant.

[topperc]

The ARM/AArch64 definition also look redundant.

ARM/AArch64 has callers and they don't populate the DenseMap in MCRegisterInfo like X86_MC::initLLVMToSEHAndCVRegMapping unless I missed it?

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-armv8-quick running on linaro-clang-armv8-quick while building llvm at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/3663

Here is the relevant piece of the build log for the reference

Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'ClangPseudo :: crash/backslashes.c' FAILED ********************
Exit Code: 134

Command Output (stderr):
--
RUN: at line 2: clang-pseudo -source=/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/crash/backslashes.c -print-tokens
+ clang-pseudo -source=/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/crash/backslashes.c -print-tokens
clang-pseudo: ../llvm/clang-tools-extra/pseudo/lib/cxx/CXX.cpp:437: auto clang::pseudo::cxx::getLanguage()::(anonymous class)::operator()() const: Assertion `Diags.empty()' failed.
#0 0x00c5535c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang-pseudo+0x5f35c)
#1 0x00c530e4 llvm::sys::RunSignalHandlers() (/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang-pseudo+0x5d0e4)
#2 0x00c55db0 SignalHandler(int) Signals.cpp:0:0
#3 0xf7b7d6e0 __default_sa_restorer ./signal/../sysdeps/unix/sysv/linux/arm/sigrestorer.S:67:0
#4 0xf7b6db06 ./csu/../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:47:0
#5 0xf7bad292 __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#6 0xf7b7c840 gsignal ./signal/../sysdeps/posix/raise.c:27:6
/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/tools/clang/tools/extra/pseudo/test/crash/Output/backslashes.c.script: line 1: 2031102 Aborted                 clang-pseudo -source=/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/crash/backslashes.c -print-tokens

--

********************

[phoebewang]

The ARM/AArch64 definition also look redundant.

ARM/AArch64 has callers and they don't populate the DenseMap in MCRegisterInfo like X86_MC::initLLVMToSEHAndCVRegMapping unless I missed it?

That's interesting. I saw MCStreamer::emitWinCFIPushReg will call getSEHRegNum and think it should work for ARM/AArch64 too.