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Merge pull request #6227 from JesseRMeyer/lto-support

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Fix LTO on Windows
This commit is contained in:
gingerBill
2026-02-04 08:59:23 +00:00
committed by GitHub
parent 270df36468 b8276065f9
commit 61f3d45fa7
4 changed files with 49 additions and 18 deletions
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2
src/linker.cpp
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@@ -331,7 +331,7 @@ try_cross_linking:;
gbString lld_lto_flags = gb_string_make(heap_allocator(), "");
defer (gb_string_free(lld_lto_flags));
if (build_context.lto_kind != LTO_None) {
lld_lto_flags = gb_string_append_fmt(lld_lto_flags, "/lldltojobs:%d ", build_context.thread_count);
lld_lto_flags = gb_string_append_fmt(lld_lto_flags, "/opt:lldltojobs=%d ", build_context.thread_count);
}
switch (build_context.linker_choice) {

23
src/llvm_backend.cpp
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@@ -2454,14 +2454,21 @@ gb_internal WORKER_TASK_PROC(lb_llvm_module_pass_worker_proc) {
// tsan - Linux, Darwin
// ubsan - Linux, Darwin, Windows (NOT SUPPORTED WITH LLVM C-API)
if (build_context.sanitizer_flags & SanitizerFlag_Address) {
array_add(&passes, "asan");
}
if (build_context.sanitizer_flags & SanitizerFlag_Memory) {
array_add(&passes, "msan");
}
if (build_context.sanitizer_flags & SanitizerFlag_Thread) {
array_add(&passes, "tsan");
// With LTO, sanitizer passes run at link time (via -fsanitize= linker flags)
// where the linker has whole-program visibility. Running them here too would
// double-instrument every module, producing "Redundant instrumentation" warnings.
// Per-function sanitize attributes in the bitcode are preserved and respected
// by the linker's sanitizer pass.
if (build_context.lto_kind == LTO_None) {
if (build_context.sanitizer_flags & SanitizerFlag_Address) {
array_add(&passes, "asan");
}
if (build_context.sanitizer_flags & SanitizerFlag_Memory) {
array_add(&passes, "msan");
}
if (build_context.sanitizer_flags & SanitizerFlag_Thread) {
array_add(&passes, "tsan");
}
}
if (passes.count == 0) {

29
src/llvm_backend_opt.cpp
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@@ -512,8 +512,9 @@ gb_internal void llvm_delete_function(LLVMValueRef func) {
LLVMDeleteFunction(func);
}
gb_internal void lb_append_to_compiler_used(lbModule *m, LLVMValueRef value) {
LLVMValueRef global = LLVMGetNamedGlobal(m->mod, "llvm.compiler.used");
// Helper to append a value to an llvm metadata array global (llvm.used or llvm.compiler.used)
gb_internal void lb_append_to_llvm_used_list(lbModule *m, LLVMValueRef value, char const *list_name) {
LLVMValueRef global = LLVMGetNamedGlobal(m->mod, list_name);
LLVMValueRef *constants;
int operands = 1;
@@ -543,33 +544,43 @@ gb_internal void lb_append_to_compiler_used(lbModule *m, LLVMValueRef value) {
constants[operands - 1] = LLVMConstBitCast(value, Int8PtrTy);
LLVMValueRef initializer = LLVMConstArray(Int8PtrTy, constants, operands);
global = LLVMAddGlobal(m->mod, ATy, "llvm.compiler.used");
global = LLVMAddGlobal(m->mod, ATy, list_name);
LLVMSetLinkage(global, LLVMAppendingLinkage);
LLVMSetSection(global, "llvm.metadata");
LLVMSetInitializer(global, initializer);
}
gb_internal void lb_append_to_compiler_used(lbModule *m, LLVMValueRef value) {
lb_append_to_llvm_used_list(m, value, "llvm.compiler.used");
}
// llvm.used survives LTO linker optimizations (unlike llvm.compiler.used)
gb_internal void lb_append_to_used(lbModule *m, LLVMValueRef value) {
lb_append_to_llvm_used_list(m, value, "llvm.used");
}
gb_internal void lb_run_remove_unused_function_pass(lbModule *m) {
isize removal_count = 0;
isize pass_count = 0;
isize const max_pass_count = 10;
// Custom remove dead function pass
// Custom remove dead function pass (for internal linkage functions)
for (; pass_count < max_pass_count; pass_count++) {
bool was_dead = false;
bool was_dead = false;
for (LLVMValueRef func = LLVMGetFirstFunction(m->mod);
func != nullptr;
/**/
) {
LLVMValueRef curr_func = func;
func = LLVMGetNextFunction(func);
LLVMUseRef first_use = LLVMGetFirstUse(curr_func);
if (first_use != nullptr) {
continue;
}
String name = {};
name.text = cast(u8 *)LLVMGetValueName2(curr_func, cast(size_t *)&name.len);
if (LLVMIsDeclaration(curr_func)) {
// Ignore for the time being
continue;
@@ -578,7 +589,7 @@ gb_internal void lb_run_remove_unused_function_pass(lbModule *m) {
if (linkage != LLVMInternalLinkage) {
continue;
}
Entity **found = map_get(&m->procedure_values, curr_func);
if (found && *found) {
Entity *e = *found;
@@ -588,7 +599,7 @@ gb_internal void lb_run_remove_unused_function_pass(lbModule *m) {
continue;
}
}
llvm_delete_function(curr_func);
was_dead = true;
removal_count += 1;

13
src/llvm_backend_proc.cpp
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@@ -289,6 +289,19 @@ gb_internal lbProcedure *lb_create_procedure(lbModule *m, Entity *entity, bool i
lb_set_linkage_from_entity_flags(p->module, p->value, entity->flags);
// With LTO on Windows, required procedures with external linkage need to be added to
// llvm.used to survive linker-level dead code elimination. This is necessary because
// LLVM may generate implicit calls to runtime builtins (e.g., __extendhfsf2 for f16
// conversions) during instruction lowering, after the IR is finalized.
if (build_context.lto_kind != LTO_None && build_context.metrics.os == TargetOs_windows) {
if (entity->flags & EntityFlag_Require) {
LLVMLinkage linkage = LLVMGetLinkage(p->value);
if (linkage != LLVMInternalLinkage) {
lb_append_to_used(m, p->value);
}
}
}
if (m->debug_builder) { // Debug Information
Type *bt = base_type(p->type);