stage2: introduce clangAssemblerSupportsMcpuArg

Clang has a completely inconsistent CLI for its integrated assembler for
each target architecture. For x86_64, for example, it does not accept
an -mcpu parameter, and emits "warning: unused parameter". However, for
ARM, -mcpu is needed in order to properly lower assembly to machine code
instructions (see new standalone test case provided thanks to @g-w1).

This is a compromise between
b8f85a805bf61ae11d6ee2bd6d8356fbc98ee3ba and
afb9f695b1bdbf81185e7d55d5783bcbab880989.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/target.zig b/src/target.zig
index e077d9629c..b4e6123819 100644
--- a/src/target.zig
+++ b/src/target.zig
@@ -389,3 +389,12 @@ pub fn clangMightShellOutForAssembly(target: std.Target) bool {
     // when targeting a non-BSD OS.
     return target.cpu.arch.isSPARC();
 }
+
+/// Each backend architecture in Clang has a different codepath which may or may not
+/// support an -mcpu flag.
+pub fn clangAssemblerSupportsMcpuArg(target: std.Target) bool {
+    return switch (target.cpu.arch) {
+        .arm, .armeb, .thumb, .thumbeb => true,
+        else => false,
+    };
+}