[PATCH 088/203] Introduce ternop_cond_operation

Tom Tromey
2021-01-01T21:48:29Z

This adds class ternop_cond_operation, which implements TERNOP_COND.

gdb/ChangeLog
2021-01-01 Tom Tromey <tom@tromey.com>

* expop.h (class ternop_cond_operation): New.
* ax-gdb.c (ternop_cond_operation::do_generate_ax): New method.
---
gdb/ChangeLog | 5 +++++
gdb/ax-gdb.c | 29 +++++++++++++++++++++++++++++
gdb/expop.h | 31 +++++++++++++++++++++++++++++++
3 files changed, 65 insertions(+)

diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
index e25e2942475..87aa2107872 100644
--- a/gdb/ax-gdb.c
+++ b/gdb/ax-gdb.c
@@ -2390,6 +2390,35 @@ internalvar_operation::do_generate_ax (struct expression *exp,
"expressions cannot use convenience variables."), name);
}

+void
+ternop_cond_operation::do_generate_ax (struct expression *exp,
+ struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *cast_type)
+{
+ struct axs_value value1, value2, value3;
+ int if1, end;
+
+ std::get<0> (m_storage)->generate_ax (exp, ax, &value1);
+ gen_usual_unary (ax, &value1);
+ /* For (A ? B : C), it's easiest to generate subexpression
+ bytecodes in order, but if_goto jumps on true, so we invert
+ the sense of A. Then we can do B by dropping through, and
+ jump to do C. */
+ gen_logical_not (ax, &value1, builtin_type (ax->gdbarch)->builtin_int);
+ if1 = ax_goto (ax, aop_if_goto);
+ std::get<1> (m_storage)->generate_ax (exp, ax, &value2);
+ gen_usual_unary (ax, &value2);
+ end = ax_goto (ax, aop_goto);
+ ax_label (ax, if1, ax->len);
+ std::get<2> (m_storage)->generate_ax (exp, ax, &value3);
+ gen_usual_unary (ax, &value3);
+ ax_label (ax, end, ax->len);
+ /* This is arbitrary - what if B and C are incompatible types? */
+ value->type = value2.type;
+ value->kind = value2.kind;
+}
+
}

/* This handles the middle-to-right-side of code generation for binary
diff --git a/gdb/expop.h b/gdb/expop.h
index 49a03ce70c6..0bb9e081df0 100644
--- a/gdb/expop.h
+++ b/gdb/expop.h
@@ -723,6 +723,37 @@ class ternop_slice_operation
{ return TERNOP_SLICE; }
};

+class ternop_cond_operation
+ : public maybe_constant_operation<operation_up, operation_up, operation_up>
+{
+public:
+
+ using maybe_constant_operation::maybe_constant_operation;
+
+ value *evaluate (struct type *expect_type,
+ struct expression *exp,
+ enum noside noside) override
+ {
+ struct value *val
+ = std::get<0> (m_storage)->evaluate (nullptr, exp, noside);
+
+ if (value_logical_not (val))
+ return std::get<2> (m_storage)->evaluate (nullptr, exp, noside);
+ return std::get<1> (m_storage)->evaluate (nullptr, exp, noside);
+ }
+
+ enum exp_opcode opcode () const override
+ { return TERNOP_COND; }
+
+protected:
+
+ void do_generate_ax (struct expression *exp,
+ struct agent_expr *ax,
+ struct axs_value *value,
+ struct type *cast_type)
+ override;
+};
+
} /* namespace expr */

#endif /* EXPOP_H */
--
2.26.2