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fix ccom idempotency

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ccom may be called multiple times on the same
node, via 'goto loop' calls from the commute
label, OADD, and a few other places.

Casts to void could null out the LHS of the
node, which would cause the compiler to crash
if the cast was revisited due to one of these
cases, because we tried frobbing n->left.

Now, if n->left is nil, we just return.w
This commit is contained in:
Ori Bernstein 2020-03-15 15:08:04 -07:00
parent 5bc9b0c3ca
commit 52dc943702
1 changed files with 4 additions and 1 deletions
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5
sys/src/cmd/cc/com.c
View file

@ -1018,6 +1018,8 @@ if(debug['y']) prtree(n, "final");
* remove some zero operands
* remove no op casts
* evaluate constants
* Note: ccom may be called on the same node
* multiple times.
*/
void
ccom(Node *n)
@ -1078,8 +1080,9 @@ loop:
if(n->type == types[TVOID] && !side(l)){
n->left = Z;
n->type = T;
break;
}
if(n->left == Z)
break;
if(castucom(n))
warn(n, "32-bit unsigned complement zero-extended to 64 bits");
ccom(l);