[X86] Fix SLH crash on llvm.eh.sjlh.longjmp (#77959)

Fix #60081.

Author: nmosier

llvm/lib/Target/X86/X86SpeculativeLoadHardening.cpp

@@ -1840,7 +1840,7 @@ MachineInstr *X86SpeculativeLoadHardeningPass::sinkPostLoadHardenedInst(
       // just bail. Also check that its register class is one of the ones we
       // can harden.
       Register UseDefReg = UseMI.getOperand(0).getReg();
-      if (!UseDefReg.isVirtual() || !canHardenRegister(UseDefReg))
+      if (!canHardenRegister(UseDefReg))
         return {};
 
       SingleUseMI = &UseMI;
@@ -1863,6 +1863,10 @@ MachineInstr *X86SpeculativeLoadHardeningPass::sinkPostLoadHardenedInst(
 }
 
 bool X86SpeculativeLoadHardeningPass::canHardenRegister(Register Reg) {
+  // We only support hardening virtual registers.
+  if (!Reg.isVirtual())
+    return false;
+
   auto *RC = MRI->getRegClass(Reg);
   int RegBytes = TRI->getRegSizeInBits(*RC) / 8;
   if (RegBytes > 8)
@@ -1909,7 +1913,6 @@ unsigned X86SpeculativeLoadHardeningPass::hardenValueInRegister(
     Register Reg, MachineBasicBlock &MBB, MachineBasicBlock::iterator InsertPt,
     const DebugLoc &Loc) {
   assert(canHardenRegister(Reg) && "Cannot harden this register!");
-  assert(Reg.isVirtual() && "Cannot harden a physical register!");
 
   auto *RC = MRI->getRegClass(Reg);
   int Bytes = TRI->getRegSizeInBits(*RC) / 8;

llvm/test/CodeGen/X86/speculative-load-hardening.ll

@@ -1161,3 +1161,34 @@ define void @idempotent_atomic(ptr %x) speculative_load_hardening {
   %tmp = atomicrmw or ptr %x, i32 0 seq_cst
   ret void
 }
+
+; Make sure we don't crash on longjmps (PR60081).
+declare void @llvm.eh.sjlj.longjmp(ptr)
+define void @test_longjmp(ptr %env) speculative_load_hardening {
+; X64-LABEL: test_longjmp:
+; X64:       # %bb.0:
+; X64-NEXT:    pushq %rbp
+; X64-NEXT:    .cfi_def_cfa_offset 16
+; X64-NEXT:    .cfi_offset %rbp, -16
+; X64-NEXT:    movq %rsp, %rax
+; X64-NEXT:    movq $-1, %rcx
+; X64-NEXT:    sarq $63, %rax
+; X64-NEXT:    orq %rax, %rdi
+; X64-NEXT:    movq (%rdi), %rbp
+; X64-NEXT:    movq 8(%rdi), %rcx
+; X64-NEXT:    movq 16(%rdi), %rsp
+; X64-NEXT:    orq %rax, %rcx
+; X64-NEXT:    jmpq *%rcx
+;
+; X64-LFENCE-LABEL: test_longjmp:
+; X64-LFENCE:       # %bb.0:
+; X64-LFENCE-NEXT:    pushq %rbp
+; X64-LFENCE-NEXT:    .cfi_def_cfa_offset 16
+; X64-LFENCE-NEXT:    .cfi_offset %rbp, -16
+; X64-LFENCE-NEXT:    movq (%rdi), %rbp
+; X64-LFENCE-NEXT:    movq 8(%rdi), %rax
+; X64-LFENCE-NEXT:    movq 16(%rdi), %rsp
+; X64-LFENCE-NEXT:    jmpq *%rax
+  call void @llvm.eh.sjlj.longjmp(ptr %env)
+  unreachable
+}