Compilation: fix compiler_rt and ubsan_rt strategy logic

It doesn't really make sense for `target_util.canBuildLibCompilerRt`
(and its ubsan-rt friend) to take in `use_llvm`, because the caller
doesn't control that: they're just going to queue a sub-compilation for
the runtime. The only exception to that is the ZCU strategy, where we
effectively embed `_ = @import("compiler_rt")` into the Zig compilation:
there, the question does matter. Rather than trying to do multiple weird
calls to model this, just have `canBuildLibCompilerRt` return not just a
boolean, but also differentiate the self-hosted backend being capable of
building the library vs only LLVM being capable. Logic in `Compilation`
uses that difference to decide whether to use the ZCU strategy, and also
to disable the library if the compiler does not support LLVM and it is
required.

Also, remove a redundant check later on, when actually queuing jobs.
We've already checked that we can build `compiler_rt`, and
`compiler_rt_strat` is set accordingly. I'm guessing this was there to
work around a bug I saw in the old strategy assignment, where support
was ignored in some cases.

Resolves: #24623

1 files changed, 17 insertions, 19 deletions

diff --git a/src/target.zig b/src/target.zig
index b0fc3dd070..ee9d39fbf3 100644
--- a/src/target.zig
+++ b/src/target.zig
@@ -351,43 +351,41 @@ pub fn defaultCompilerRtOptimizeMode(target: *const std.Target) std.builtin.Opti
     }
 }
 
-pub fn canBuildLibCompilerRt(target: *const std.Target, use_llvm: bool, have_llvm: bool) bool {
+pub fn canBuildLibCompilerRt(target: *const std.Target) enum { no, yes, llvm_only } {
     switch (target.os.tag) {
-        .plan9 => return false,
+        .plan9 => return .no,
         else => {},
     }
     switch (target.cpu.arch) {
-        .spirv32, .spirv64 => return false,
+        .spirv32, .spirv64 => return .no,
         // Remove this once https://github.com/ziglang/zig/issues/23714 is fixed
-        .amdgcn => return false,
+        .amdgcn => return .no,
         else => {},
     }
-    return switch (zigBackend(target, use_llvm)) {
-        .stage2_aarch64 => true,
-        .stage2_llvm => true,
+    return switch (zigBackend(target, false)) {
+        .stage2_aarch64 => .yes,
         .stage2_x86_64 => switch (target.ofmt) {
-            .elf, .macho => true,
-            else => have_llvm,
+            .elf, .macho => .yes,
+            else => .llvm_only,
         },
-        else => have_llvm,
+        else => .llvm_only,
     };
 }
 
-pub fn canBuildLibUbsanRt(target: *const std.Target, use_llvm: bool, have_llvm: bool) bool {
+pub fn canBuildLibUbsanRt(target: *const std.Target) enum { no, yes, llvm_only, llvm_lld_only } {
     switch (target.cpu.arch) {
-        .spirv32, .spirv64 => return false,
+        .spirv32, .spirv64 => return .no,
         // Remove this once https://github.com/ziglang/zig/issues/23715 is fixed
-        .nvptx, .nvptx64 => return false,
+        .nvptx, .nvptx64 => return .no,
         else => {},
     }
-    return switch (zigBackend(target, use_llvm)) {
-        .stage2_llvm => true,
-        .stage2_wasm => false,
+    return switch (zigBackend(target, false)) {
+        .stage2_wasm => .llvm_lld_only,
         .stage2_x86_64 => switch (target.ofmt) {
-            .elf, .macho => true,
-            else => have_llvm,
+            .elf, .macho => .yes,
+            else => .llvm_only,
         },
-        else => have_llvm,
+        else => .llvm_only,
     };
 }