diff --git a/llvm/lib/CodeGen/BasicBlockSections.cpp b/llvm/lib/CodeGen/BasicBlockSections.cpp index 1eedfc4b25912..a7ffc2e03b838 100644 --- a/llvm/lib/CodeGen/BasicBlockSections.cpp +++ b/llvm/lib/CodeGen/BasicBlockSections.cpp @@ -265,8 +265,16 @@ void llvm::sortBasicBlocksAndUpdateBranches( // zero implies "no landing pad." This function inserts a NOP just before the EH // pad label to ensure a nonzero offset. void llvm::avoidZeroOffsetLandingPad(MachineFunction &MF) { + std::optional CurrentSection; + auto IsFirstNonEmptyBBInSection = [&](const MachineBasicBlock &MBB) { + if (MBB.empty() || MBB.getSectionID() == CurrentSection) + return false; + CurrentSection = MBB.getSectionID(); + return true; + }; + for (auto &MBB : MF) { - if (MBB.isBeginSection() && MBB.isEHPad()) { + if (IsFirstNonEmptyBBInSection(MBB) && MBB.isEHPad()) { MachineBasicBlock::iterator MI = MBB.begin(); while (!MI->isEHLabel()) ++MI; diff --git a/llvm/test/CodeGen/Generic/machine-function-splitter.ll b/llvm/test/CodeGen/Generic/machine-function-splitter.ll index 1a8c9ede8f8b7..d798b2875645b 100644 --- a/llvm/test/CodeGen/Generic/machine-function-splitter.ll +++ b/llvm/test/CodeGen/Generic/machine-function-splitter.ll @@ -674,6 +674,36 @@ define void @foo22(i1 zeroext %0) nounwind !prof !14 !section_prefix !15 { ret void } +define i32 @foo23(i1 zeroext %0) personality ptr @__gxx_personality_v0 !prof !14 { +;; Check that nop is inserted just before the EH pad if it is the first +;; instruction in a section (but is preceeded by another empty block). +; MFS-DEFAULTS-LABEL: foo23 +; MFS-DEFAULTS-X86-LABEL: callq baz +; MFS-DEFAULTS-X86: .section .text.split.foo23,"ax",@progbits +; MFS-DEFAULTS-X86-NEXT: foo23.cold: +; MFS-DEFAULTS-X86: nop +; MFS-DEFAULTS-X86: callq _Unwind_Resume@PLT +entry: + br i1 %0, label %try, label %unreachable, !prof !17 + +try: + invoke void @_Z1fv() + to label %try.cont unwind label %lpad, !prof !17 + +try.cont: + %1 = call i32 @baz() + ret i32 %1 + +unreachable: + unreachable + +lpad: + %2 = landingpad { ptr, i32 } + cleanup + catch ptr @_ZTIi + resume { ptr, i32 } %2 +} + declare i32 @bar() declare i32 @baz() declare i32 @bam()