harec

commit f72a9f03cf843b58780c08f0788ed83aa616691d
parent ef3e7d022fcfaeeda8a7bb9a133a1e33a55e4305
Author: Sebastian <sebastian@sebsite.pw>
Date:   Mon, 10 Oct 2022 18:27:22 -0400

gen: don't directly use jnz on longs

jnz always operates on words. Because of this, there are rare cases
where the lower 32 bits of an integer are zero, but the upper 32 bits
aren't, so the code branches incorrectly. This is fixed by using cnel
(or a similar comparison function) first, and then using the return
value of that as the first operand to jnz.

Signed-off-by: Sebastian <sebastian@sebsite.pw>

Diffstat:
M
src/gen.c
 | 
41
++++++++++++++++++++++++-----------------

1 file changed, 24 insertions(+), 17 deletions(-)
diff --git a/src/gen.c b/src/gen.c
@@ -441,7 +441,8 @@ gen_alloc_slice_at(struct gen_context *ctx,
 
 	struct qbe_statement linvalid;
 	struct qbe_value binvalid = mklabel(ctx, &linvalid, ".%d");
-	pushi(ctx->current, NULL, Q_JNZ, &data, &bzero, &binvalid, NULL);
+	pushi(ctx->current, &cmpres, Q_CNEL, &size, &zero, NULL);
+	pushi(ctx->current, NULL, Q_JNZ, &cmpres, &bzero, &binvalid, NULL);
 	push(&ctx->current->body, &linvalid);
 	gen_fixed_abort(ctx, expr->loc, ABORT_ALLOC_FAILURE);
 	push(&ctx->current->body, &lzero);
@@ -511,10 +512,13 @@ gen_expr_alloc_init_with(struct gen_context *ctx,
 
 	if (!(type_dealias(expr->result)->pointer.flags & PTR_NULLABLE)) {
 		struct qbe_statement linvalid, lvalid;
+		struct qbe_value cmpres = mkqtmp(ctx, &qbe_word, ".%d");
+		struct qbe_value zero = constl(0);
 		struct qbe_value binvalid = mklabel(ctx, &linvalid, ".%d");
 		struct qbe_value bvalid = mklabel(ctx, &lvalid, ".%d");
 
-		pushi(ctx->current, NULL, Q_JNZ, &qresult, &bvalid, &binvalid, NULL);
+		pushi(ctx->current, &cmpres, Q_CNEL, &qresult, &zero, NULL);
+		pushi(ctx->current, NULL, Q_JNZ, &cmpres, &bvalid, &binvalid, NULL);
 		push(&ctx->current->body, &linvalid);
 		gen_fixed_abort(ctx, expr->loc, ABORT_ALLOC_FAILURE);
 		push(&ctx->current->body, &lvalid);
@@ -600,10 +604,12 @@ gen_expr_alloc_copy_with(struct gen_context *ctx,
 	struct qbe_value binvalid = mklabel(ctx, &linvalid, ".%d");
 	struct qbe_value bvalid = mklabel(ctx, &lvalid, ".%d");
 
+	struct qbe_value cmpres = mkqtmp(ctx, &qbe_word, ".%d");
 	struct qbe_value newdata = mkqtmp(ctx, ctx->arch.ptr, ".%d");
 	struct qbe_value zero = constl(0);
 	pushi(ctx->current, &newdata, Q_COPY, &zero, NULL);
-	pushi(ctx->current, NULL, Q_JNZ, &length, &balloc, &bvalid, NULL);
+	pushi(ctx->current, &cmpres, Q_CNEL, &length, &zero, NULL);
+	pushi(ctx->current, NULL, Q_JNZ, &cmpres, &balloc, &bvalid, NULL);
 	push(&ctx->current->body, &lalloc);
 
 	const struct type *result = type_dealias(expr->result);
@@ -615,7 +621,8 @@ gen_expr_alloc_copy_with(struct gen_context *ctx,
 	struct qbe_value rtfunc = mkrtfunc(ctx, "rt.malloc");
 	pushi(ctx->current, &newdata, Q_CALL, &rtfunc, &sz, NULL);
 
-	pushi(ctx->current, NULL, Q_JNZ, &newdata, &bvalid, &binvalid, NULL);
+	pushi(ctx->current, &cmpres, Q_CNEL, &newdata, &zero, NULL);
+	pushi(ctx->current, NULL, Q_JNZ, &cmpres, &bvalid, &binvalid, NULL);
 	push(&ctx->current->body, &linvalid);
 	gen_fixed_abort(ctx, expr->loc, ABORT_ALLOC_FAILURE);
 	push(&ctx->current->body, &lvalid);
@@ -1540,13 +1547,13 @@ gen_expr_cast(struct gen_context *ctx, const struct expression *expr)
 
 		struct gen_value val = gen_expr(ctx, expr->cast.value);
 		struct qbe_value qval = mkqval(ctx, &val);
+		struct qbe_value zero = constl(0);
+		enum qbe_instr compare = want_null ? Q_CEQL : Q_CNEL;
 		if (expr->cast.kind == C_TEST) {
 			struct gen_value out =
 				mkgtemp(ctx, &builtin_type_bool, ".%d");
 			struct qbe_value qout = mkqval(ctx, &out);
-			struct qbe_value zero = constl(0);
 
-			enum qbe_instr compare = want_null? Q_CEQL : Q_CNEL;
 			pushi(ctx->current, &qout, compare, &qval, &zero, NULL);
 			return out;
 		} else if (expr->cast.kind == C_ASSERTION) {
@@ -1556,13 +1563,10 @@ gen_expr_cast(struct gen_context *ctx, const struct expression *expr)
 			struct qbe_value bpassed =
 				mklabel(ctx, &passedl, "passed.%d");
 
-			if (want_null) {
-				pushi(ctx->current, NULL, Q_JNZ, &qval,
-					&bfailed, &bpassed, NULL);
-			} else {
-				pushi(ctx->current, NULL, Q_JNZ, &qval,
-					&bpassed, &bfailed, NULL);
-			}
+			struct qbe_value cmpres = mkqtmp(ctx, &qbe_word, ".%d");
+			pushi(ctx->current, &cmpres, compare, &qval, &zero, NULL);
+			pushi(ctx->current, NULL, Q_JNZ, &cmpres,
+				&bpassed, &bfailed, NULL);
 			push(&ctx->current->body, &failedl);
 			gen_fixed_abort(ctx, expr->loc, ABORT_TYPE_ASSERTION);
 
@@ -2581,6 +2585,7 @@ gen_match_with_nullable(struct gen_context *ctx,
 	struct qbe_value bout = mklabel(ctx, &lout, ".%d");
 	struct gen_value object = gen_expr(ctx, expr->match.value);
 	struct qbe_value qobject = mkqval(ctx, &object);
+	struct qbe_value zero = constl(0);
 
 	struct gen_value bval;
 	const struct match_case *_default = NULL;
@@ -2592,16 +2597,18 @@ gen_match_with_nullable(struct gen_context *ctx,
 		}
 
 		struct qbe_statement lmatch, lnext;
+		struct qbe_value cmpres = mkqtmp(ctx, &qbe_word, ".%d");
 		struct qbe_value bmatch = mklabel(ctx, &lmatch, "matches.%d");
 		struct qbe_value bnext = mklabel(ctx, &lnext, "next.%d");
 
+		enum qbe_instr compare;
 		if (_case->type->storage == STORAGE_NULL) {
-			pushi(ctx->current, NULL, Q_JNZ,
-				&qobject, &bnext, &bmatch, NULL);
+			compare = Q_CEQL;
 		} else {
-			pushi(ctx->current, NULL, Q_JNZ,
-				&qobject, &bmatch, &bnext, NULL);
+			compare = Q_CNEL;
 		}
+		pushi(ctx->current, &cmpres, compare, &qobject, &zero, NULL);
+		pushi(ctx->current, NULL, Q_JNZ, &cmpres, &bmatch, &bnext, NULL);
 
 		push(&ctx->current->body, &lmatch);