From 91fa2c61aacd002228c37cb651fa0a350bd7ac59 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= Date: Fri, 3 Oct 2025 03:22:02 +0200 Subject: [PATCH] compiler: control the s390x backchain feature through the frame pointer option This is a little different from how C/C++ compilers do this, but I think it's justified because it's what users actually *mean* when the use frame pointer options. This is another one of those LLVM "CPU" features that have nothing to do with CPU at all and should really be a TargetMachine option or something. One day we'll figure out a better way of dealing with these... --- src/Compilation.zig | 8 ++++++-- src/Package/Module.zig | 5 ++++- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/src/Compilation.zig b/src/Compilation.zig index 86b1356a3f..f13a232e47 100644 --- a/src/Compilation.zig +++ b/src/Compilation.zig @@ -7193,6 +7193,9 @@ pub fn addCCArgs( } try argv.append(if (mod.omit_frame_pointer) "-fomit-frame-pointer" else "-fno-omit-frame-pointer"); + if (target.cpu.arch == .s390x) { + try argv.append(if (mod.omit_frame_pointer) "-mbackchain" else "-mno-backchain"); + } const ssp_buf_size = mod.stack_protector; if (ssp_buf_size != 0) { @@ -7258,9 +7261,10 @@ pub fn addCCArgs( const is_enabled = target.cpu.features.isEnabled(index); if (feature.llvm_name) |llvm_name| { - // We communicate float ABI to Clang through the dedicated options. + // We communicate these to Clang through the dedicated options. if (std.mem.startsWith(u8, llvm_name, "soft-float") or - std.mem.startsWith(u8, llvm_name, "hard-float")) + std.mem.startsWith(u8, llvm_name, "hard-float") or + (target.cpu.arch == .s390x and std.mem.eql(u8, llvm_name, "backchain"))) continue; // Ignore these until we figure out how to handle the concept of omitting features. diff --git a/src/Package/Module.zig b/src/Package/Module.zig index 440f764b31..cd7f573046 100644 --- a/src/Package/Module.zig +++ b/src/Package/Module.zig @@ -343,7 +343,10 @@ pub fn create(arena: Allocator, options: CreateOptions) !*Package.Module { // See https://github.com/ziglang/zig/issues/23539 if (target_util.isDynamicAMDGCNFeature(target, feature)) continue; - const is_enabled = target.cpu.features.isEnabled(feature.index); + var is_enabled = target.cpu.features.isEnabled(feature.index); + if (target.cpu.arch == .s390x and @as(std.Target.s390x.Feature, @enumFromInt(feature.index)) == .backchain) { + is_enabled = !omit_frame_pointer; + } if (is_enabled) { try buf.ensureUnusedCapacity(2 + llvm_name.len);