zig

commit b36cfc6352df4c5c5005c7a720dbc84894097d11 (tree)
parent 2ac47fe314f0a88a2e5ac6c0116392504369b466
Author: Matthew Lugg <mlugg@mlugg.co.uk>
Date:   Sat, 28 Mar 2026 09:53:13 +0000

compiler-rt: work around LLVM not respecting -fno-builtin

Diffstat:
M
lib/compiler_rt/mulo.zig
 | 
7
++++++-

1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/lib/compiler_rt/mulo.zig b/lib/compiler_rt/mulo.zig
@@ -19,7 +19,12 @@ comptime {
 inline fn muloXi4_genericSmall(comptime ST: type, a: ST, b: ST, overflow: *c_int) ST {
     overflow.* = 0;
     const min = math.minInt(ST);
-    const res: ST = a *% b;
+    const res: ST = if (ST == i128 and builtin.target.cpu.arch.isWasm()) res: {
+        // Despite compiler-rt being built with `-fno-builtin`, LLVM still converts this function to
+        // a call to `__muloti4` on WASM. This is an upstream bug: circumvent it by directly calling
+        // the "lower-level" compiler-rt routine for this wrapping multiplication.
+        break :res @import("mulXi3.zig").__multi3(a, b);
+    } else a *% b;
     // Hacker's Delight section Overflow subsection Multiplication
     // case a=-2^{31}, b=-1 problem, because
     // on some machines a*b = -2^{31} with overflow