zig

commit 2d62c61b70e5eecacc6d7988cc084b45f86f449c (tree)
parent 427b428db822b587541816df24f32cb9edd9a072
Author: Motiejus <motiejus@jakstys.lt>
Date:   Sat,  7 Mar 2026 08:06:09 +0000

sema: add comptime float folding to zirNegate

For comptime-known float operands, compute -val at comptime instead of
emitting AIR_INST_NEG. Matches src/Sema.zig zirNegate: arith.negateFloat
for comptime values, preserving negative zero semantics.

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

Diffstat:
M
stage0/sema.c
 | 
17
+++++++++++++++--

1 file changed, 15 insertions(+), 2 deletions(-)
diff --git a/stage0/sema.c b/stage0/sema.c
@@ -943,9 +943,22 @@ static AirInstRef zirNegate(Sema* sema, SemaBlock* block, uint32_t inst) {
     AirInstRef operand = resolveInst(sema, operand_ref);
     TypeIndex ty = semaTypeOf(sema, operand);
 
-    // Float negation: emit AIR_INST_NEG directly.
-    // Ported from src/Sema.zig zirNegate float branch.
+    // Float negation: fold at comptime if known, else emit AIR_INST_NEG.
+    // Ported from src/Sema.zig zirNegate float branch (arith.negateFloat).
     if (floatBits(ty) > 0) {
+        if (AIR_REF_IS_IP(operand)) {
+            InternPoolKey src_key
+                = ipIndexToKey(sema->ip, AIR_REF_TO_IP(operand));
+            if (src_key.tag == IP_KEY_FLOAT) {
+                // Negate preserving negative zero semantics.
+                InternPoolKey result_key;
+                memset(&result_key, 0, sizeof(result_key));
+                result_key.tag = IP_KEY_FLOAT;
+                result_key.data.float_val.ty = ty;
+                result_key.data.float_val.val = -src_key.data.float_val.val;
+                return AIR_REF_FROM_IP(ipIntern(sema->ip, result_key));
+            }
+        }
         AirInstData data;
         memset(&data, 0, sizeof(data));
         data.ty_op.ty_ref = AIR_REF_FROM_IP(ty);