From: Dale Weiler <killfieldengine@gmail.com>
Date: Mon, 9 Dec 2013 00:01:44 +0000 (-0500)
Subject: Only optimize (a - (-b)) into (a + b) when the unary operand is a negation. This... 
X-Git-Tag: xonotic-v0.8.0~35
X-Git-Url: https://git.rm.cloudns.org/?a=commitdiff_plain;h=58cd326d85f6eb67d46ecc41c111df086e836837;p=xonotic%2Fgmqcc.git

Only optimize (a - (-b)) into (a + b) when the unary operand is a negation. This fixes (a - (!b)) being turned into (a + b).
---

diff --git a/ast.c b/ast.c
index 238d00a..e10bbed 100644
--- a/ast.c
+++ b/ast.c
@@ -442,17 +442,20 @@ ast_binary* ast_binary_new(lex_ctx_t ctx, int op,
     ast_expression_init((ast_expression*)self, (ast_expression_codegen*)&ast_binary_codegen);
 
     if (ast_istype(right, ast_unary) && OPTS_OPTIMIZATION(OPTIM_PEEPHOLE)) {
-        ast_expression *normal = ((ast_unary*)right)->operand;
+        ast_unary      *unary  = ((ast_unary*)right);
+        ast_expression *normal = unary->operand;
 
         /* make a-(-b) => a + b */
-        if (op == INSTR_SUB_F) {
-            op = INSTR_ADD_F;
-            right = normal;
-            ++opts_optimizationcount[OPTIM_PEEPHOLE];
-        } else if (op == INSTR_SUB_V) {
-            op = INSTR_ADD_V;
-            right = normal;
-            ++opts_optimizationcount[OPTIM_PEEPHOLE];
+        if (unary->op == VINSTR_NEG_F || unary->op == VINSTR_NEG_V) {
+            if (op == INSTR_SUB_F) {
+                op = INSTR_ADD_F;
+                right = normal;
+                ++opts_optimizationcount[OPTIM_PEEPHOLE];
+            } else if (op == INSTR_SUB_V) {
+                op = INSTR_ADD_V;
+                right = normal;
+                ++opts_optimizationcount[OPTIM_PEEPHOLE];
+            }
         }
     }