Commit b3b96b5e288ddf3694b4a0d203c684b9b8f6b49f | zig

author	Andrew Kelley <andrew@ziglang.org> 2022-06-30 11:48:37-07:00
committer	Andrew Kelley <andrew@ziglang.org> 2022-06-30 11:48:37-07:00
log	b3b96b5e288ddf3694b4a0d203c684b9b8f6b49f
tree	93ec35c7630bdfe44eb3cf4f27e9db286d1e2b32
parent	c8531faaf56612773ef860d341f8eebb36af4bf3

Rather than a compiler-rt call in the case that LLVM does not support
lowering the fneg instruction.

1 files changed, 10 insertions(+), 4 deletions(-)

src/codegen/llvm.zig+10-4

 @@ -6598,10 +6598,16 @@ pub const FuncGen = struct {
         } else b: {
             const float_bits = scalar_ty.floatBits(target);
             break :b switch (op) {
-                .neg => FloatOpStrat{
+                .neg => {
-                    .libc = std.fmt.bufPrintZ(&fn_name_buf, "__neg{s}f2", .{
+                    // In this case we can generate a softfloat negation by XORing the
-                        compilerRtFloatAbbrev(float_bits),
+                    // bits with a constant.
-                    }) catch unreachable,
+                    const int_llvm_ty = self.dg.context.intType(float_bits);
+                    const one = int_llvm_ty.constInt(1, .False);
+                    const shift_amt = int_llvm_ty.constInt(float_bits - 1, .False);
+                    const sign_mask = one.constShl(shift_amt);
+                    const bitcasted_operand = self.builder.buildBitCast(params[0], int_llvm_ty, "");
+                    const result = self.builder.buildXor(bitcasted_operand, sign_mask, "");
+                    return self.builder.buildBitCast(result, llvm_ty, "");
                 },
                 .add, .sub, .div, .mul => FloatOpStrat{
                     .libc = std.fmt.bufPrintZ(&fn_name_buf, "__{s}{s}f3", .{