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Auto merge of #88243 - nikic:newpm-2, r=nagisa

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Enable new pass manager with LLVM 13

The new pass manager is enabled by default in clang since Clang/LLVM 13. Per the recent discussion on llvm-dev (https://lists.llvm.org/pipermail/llvm-dev/2021-August/152305.html) the legacy pass manager will be unmaintained in LLVM 14 and removed entirely in LLVM 15.

This switches us to use the new pass manager if LLVM >= 13 is used. It's possible to still use the old pass manager using `-Z new-llvm-pass-manager=no`.
This commit is contained in:
bors 2021-09-25 13:43:52 +00:00
commit 63cc2bb3d0
3 changed files with 17 additions and 8 deletions
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5
compiler/rustc_codegen_llvm/src/back/write.rs
View File

@ -370,8 +370,9 @@ fn get_pgo_use_path(config: &ModuleConfig) -> Option<CString> {
}
pub(crate) fn should_use_new_llvm_pass_manager(config: &ModuleConfig) -> bool {
// The new pass manager is disabled by default.
config.new_llvm_pass_manager.unwrap_or(false)
// The new pass manager is enabled by default for LLVM >= 13.
// This matches Clang, which also enables it since Clang 13.
config.new_llvm_pass_manager.unwrap_or_else(|| llvm_util::get_version() >= (13, 0, 0))
}
pub(crate) unsafe fn optimize_with_new_llvm_pass_manager(

5
compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
View File

@ -1004,7 +1004,10 @@ LLVMRustOptimizeWithNewPassManager(
#endif
bool NeedThinLTOBufferPasses = UseThinLTOBuffers;
if (!NoPrepopulatePasses) {
if (OptLevel == OptimizationLevel::O0) {
// The pre-link pipelines don't support O0 and require using budilO0DefaultPipeline() instead.
// At the same time, the LTO pipelines do support O0 and using them is required.
bool IsLTO = OptStage == LLVMRustOptStage::ThinLTO || OptStage == LLVMRustOptStage::FatLTO;
if (OptLevel == OptimizationLevel::O0 && !IsLTO) {
#if LLVM_VERSION_GE(12, 0)
for (const auto &C : PipelineStartEPCallbacks)
PB.registerPipelineStartEPCallback(C);

15
src/test/codegen/panic-in-drop-abort.rs
View File

@ -1,8 +1,17 @@
// compile-flags: -Z panic-in-drop=abort -O
// compile-flags: -Z panic-in-drop=abort -O -Z new-llvm-pass-manager=no
// Ensure that unwinding code paths are eliminated from the output after
// optimization.
// This test uses -Z new-llvm-pass-manager=no, because the expected optimization does not happen
// on targets using SEH exceptions (i.e. MSVC) anymore. The core issue is that Rust promises that
// the drop_in_place() function can't unwind, but implements it in a way that *can*, because we
// currently go out of our way to allow longjmps, which also use the unwinding mechanism on MSVC
// targets. We should either forbid longjmps, or not assume nounwind, making this optimization
// incompatible with the current behavior of running cleanuppads on longjmp unwinding.
// CHECK-NOT: {{(call|invoke).*}}should_not_appear_in_output
#![crate_type = "lib"]
use std::any::Any;
use std::mem::forget;
@ -35,8 +44,6 @@ impl Drop for AssertNeverDrop {
}
}
// CHECK-LABEL: normal_drop
// CHECK-NOT: should_not_appear_in_output
#[no_mangle]
pub fn normal_drop(x: ExternDrop) {
let guard = AssertNeverDrop;
@ -44,8 +51,6 @@ pub fn normal_drop(x: ExternDrop) {
forget(guard);
}
// CHECK-LABEL: indirect_drop
// CHECK-NOT: should_not_appear_in_output
#[no_mangle]
pub fn indirect_drop(x: Box<dyn Any>) {
let guard = AssertNeverDrop;