Casting to _Bool requires a zero test rather than truncation.
Signed-off-by: Xi Wang <xi.wang@xxxxxxxxx>
---
A simple example is:
_Bool x = 0x200;
x should have been true rather than false.
BTW, this patch also disables the warning "cast truncates bits from
constant value". Does that sound good?
A more serious problem is something like:
_Bool foo(int x) { return x; }
sparse emits:
scast.1 %r2 <- (32) %arg1
which makes sparse-llvm generate:
%R2 = trunc i32 %0 to i1
My experimental backend "splay" has to treat _Bool specifically to
generate:
%0 = icmp ne i32 %x, 0
Should we leave the conversion job to backends, or should we just fix
the sparse IR (e.g., emitting setne rather than scast for casts to _Bool)?
---
expand.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/expand.c b/expand.c
index 63a9075..ee818a4 100644
--- a/expand.c
+++ b/expand.c
@@ -92,6 +92,12 @@ void cast_value(struct expression *expr, struct symbol *newtype,
value = get_longlong(old);
Int:
+ // _Bool requires a zero test rather than truncation.
+ if (is_bool_type(newtype)) {
+ expr->value = value ? 1 : 0;
+ return;
+ }
+
// Truncate it to the new size
signmask = 1ULL << (new_size-1);
mask = signmask | (signmask-1);
--
1.7.9.5
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