From ffea4219b1f4ebe7c06cecc6c221cb0aab3a03ea Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Fri, 1 May 2020 19:30:17 +0900
Subject: [PATCH] Add flonum constant expression

---
 parse.c          | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
 test/constexpr.c |  6 ++++++
 2 files changed, 55 insertions(+)

diff --git a/parse.c b/parse.c
index fb75e26..7803020 100644
--- a/parse.c
+++ b/parse.c
@@ -130,6 +130,7 @@ static int64_t eval_rval(Node *node, char **label);
 static Node *assign(Token **rest, Token *tok);
 static Node *logor(Token **rest, Token *tok);
 static int64_t const_expr(Token **rest, Token *tok);
+static double eval_double(Node *node);
 static Node *conditional(Token **rest, Token *tok);
 static Node *logand(Token **rest, Token *tok);
 static Node *bitor(Token **rest, Token *tok);
@@ -1101,6 +1102,16 @@ write_gvar_data(Relocation *cur, Initializer *init, Type *ty, char *buf, int off
   if (!init->expr)
     return cur;
 
+  if (ty->kind == TY_FLOAT) {
+    *(float *)(buf + offset) = eval_double(init->expr);
+    return cur;
+  }
+
+  if (ty->kind == TY_DOUBLE) {
+    *(double *)(buf + offset) = eval_double(init->expr);
+    return cur;
+  }
+
   char *label = NULL;
   uint64_t val = eval2(init->expr, &label);
 
@@ -1427,6 +1438,9 @@ static int64_t eval(Node *node) {
 static int64_t eval2(Node *node, char **label) {
   add_type(node);
 
+  if (is_flonum(node->ty))
+    return eval_double(node);
+
   switch (node->kind) {
   case ND_ADD:
     return eval2(node->lhs, label) + eval(node->rhs);
@@ -1534,6 +1548,41 @@ static int64_t const_expr(Token **rest, Token *tok) {
   return eval(node);
 }
 
+static double eval_double(Node *node) {
+  add_type(node);
+
+  if (is_integer(node->ty)) {
+    if (node->ty->is_unsigned)
+      return (unsigned long)eval(node);
+    return eval(node);
+  }
+
+  switch (node->kind) {
+  case ND_ADD:
+    return eval_double(node->lhs) + eval_double(node->rhs);
+  case ND_SUB:
+    return eval_double(node->lhs) - eval_double(node->rhs);
+  case ND_MUL:
+    return eval_double(node->lhs) * eval_double(node->rhs);
+  case ND_DIV:
+    return eval_double(node->lhs) / eval_double(node->rhs);
+  case ND_NEG:
+    return -eval_double(node->lhs);
+  case ND_COND:
+    return eval_double(node->cond) ? eval_double(node->then) : eval_double(node->els);
+  case ND_COMMA:
+    return eval_double(node->rhs);
+  case ND_CAST:
+    if (is_flonum(node->lhs->ty))
+      return eval_double(node->lhs);
+    return eval(node->lhs);
+  case ND_NUM:
+    return node->fval;
+  }
+
+  error_tok(node->tok, "not a compile-time constant");
+}
+
 // Convert `A op= B` to `tmp = &A, *tmp = *tmp op B`
 // where tmp is a fresh pointer variable.
 static Node *to_assign(Node *binary) {
diff --git a/test/constexpr.c b/test/constexpr.c
index e32f197..3678e24 100644
--- a/test/constexpr.c
+++ b/test/constexpr.c
@@ -1,5 +1,8 @@
 #include "test.h"
 
+float g40 = 1.5;
+double g41 = 0.0 ? 55 : (0, 1 + 1 * 5.0 / 2 * (double)2 * (int)2.0);
+
 int main() {
   ASSERT(10, ({ enum { ten=1+2+3+4 }; ten; }));
   ASSERT(1, ({ int i=0; switch(3) { case 5-2+0*3: i++; } i; }));
@@ -44,6 +47,9 @@ int main() {
   ASSERT(1, ({ char x[(unsigned)1<-1]; sizeof(x); }));
   ASSERT(1, ({ char x[(unsigned)1<=-1]; sizeof(x); }));
 
+  ASSERT(1, g40==1.5);
+  ASSERT(1, g41==11);
+
   printf("OK\n");
   return 0;
 }