zig

commit 1f40a421e9ff4c246caea645f501bd1280d8f153 (tree)
parent c1a578990935ae85d566919ed19a20318cb67ebd
Author: Motiejus <motiejus@jakstys.lt>
Date:   Sat,  7 Mar 2026 11:04:36 +0000

sema: add remaining error markers for exact shifts and block_comptime

- zirShl SHR_EXACT: extend exact shift overflow check to also cover
  SHR_EXACT (shift right must not lose non-zero bits)
  (Sema.zig zirShr exact validation)
- zirBlockComptime: when body completes without break, set
  has_compile_errors and map to void instead of leaving unmapped.
  Ported from Sema.zig block_comptime semantics (break required).

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Diffstat:
M
stage0/sema.c
 | 
31
++++++++++++++++++++++++-------

1 file changed, 24 insertions(+), 7 deletions(-)
diff --git a/stage0/sema.c b/stage0/sema.c
@@ -2678,20 +2678,30 @@ static AirInstRef zirShl(
             shr128(lhs_lo, lhs_hi, shift, &r_lo, &r_hi);
         // Ported from Sema.zig zirShl lines 13943-13978:
         // For shl_exact, error if non-zero bits were shifted out.
-        if (air_tag == AIR_INST_SHL_EXACT
+        if ((air_tag == AIR_INST_SHL_EXACT || air_tag == AIR_INST_SHR_EXACT)
             && sema->ip->items[lhs_ty].tag == IP_KEY_INT_TYPE) {
             uint16_t bits = sema->ip->items[lhs_ty].data.int_type.bits;
-            // Check if shift amount >= bit width (all bits shifted out).
+            // Ported from Sema.zig zirShl/zirShr exact overflow check:
+            // Check if shift amount >= bit width.
             if (shift >= bits) {
                 sema->has_compile_errors = true;
                 return AIR_REF_FROM_IP(IP_INDEX_VOID_VALUE);
             }
-            // Check if non-zero bits were shifted out (for <= 64 bit types).
             if (bits <= 64 && shift > 0) {
-                uint64_t lost_bits_mask = UINT64_MAX << (bits - shift);
-                if (lhs_lo & lost_bits_mask) {
-                    sema->has_compile_errors = true;
-                    return AIR_REF_FROM_IP(IP_INDEX_VOID_VALUE);
+                if (air_tag == AIR_INST_SHL_EXACT) {
+                    // Check if non-zero bits were shifted out (left).
+                    uint64_t lost_bits_mask = UINT64_MAX << (bits - shift);
+                    if (lhs_lo & lost_bits_mask) {
+                        sema->has_compile_errors = true;
+                        return AIR_REF_FROM_IP(IP_INDEX_VOID_VALUE);
+                    }
+                } else {
+                    // SHR_EXACT: check if non-zero bits shifted off right.
+                    uint64_t lost_bits_mask = (UINT64_C(1) << shift) - 1;
+                    if (lhs_lo & lost_bits_mask) {
+                        sema->has_compile_errors = true;
+                        return AIR_REF_FROM_IP(IP_INDEX_VOID_VALUE);
+                    }
                 }
             }
         }
@@ -11158,6 +11168,13 @@ static void zirBlockComptime(Sema* sema, SemaBlock* block, uint32_t inst) {
             result = resolveInst(sema, operand);
         }
         instMapPut(&sema->inst_map, inst, result);
+    } else {
+        // Ported from Sema.zig block_comptime: body must end with break.
+        // If body completed without a break, the block is ill-formed.
+        // Map to void and propagate error so callers see the failure.
+        sema->has_compile_errors = true;
+        instMapPut(
+            &sema->inst_map, inst, AIR_REF_FROM_IP(IP_INDEX_VOID_VALUE));
     }
     semaBlockDeinit(&ct_block);
 }