From 3733978d9c7768baaeb6199c05bc98939c15c8cd Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Fri, 22 Feb 2019 13:48:09 -0800
Subject: Implement __builtin_nanf for empty string literals

---
 decl.h                 | 1 +
 expr.c                 | 8 ++++++++
 scope.c                | 1 +
 tests/builtin-nanf.c   | 1 +
 tests/builtin-nanf.qbe | 1 +
 5 files changed, 12 insertions(+)
 create mode 100644 tests/builtin-nanf.c
 create mode 100644 tests/builtin-nanf.qbe

diff --git a/decl.h b/decl.h
index db6a28c..314926b 100644
--- a/decl.h
+++ b/decl.h
@@ -20,6 +20,7 @@ enum builtinkind {
 	BUILTINVAEND,
 	BUILTINOFFSETOF,
 	BUILTINALLOCA,
+	BUILTINNANF,
 	BUILTININFF,
 };
 
diff --git a/expr.c b/expr.c
index 8058523..009e05f 100644
--- a/expr.c
+++ b/expr.c
@@ -450,6 +450,14 @@ builtinfunc(struct scope *s, enum builtinkind kind)
 		e->builtin.kind = BUILTINALLOCA;
 		e->builtin.arg = exprconvert(assignexpr(s), &typeulong);
 		break;
+	case BUILTINNANF:
+		e = assignexpr(s);
+		if (!(e->flags & EXPRFLAG_DECAYED) || e->unary.base->kind != EXPRSTRING || e->unary.base->string.size > 0)
+			error(&tok.loc, "__builtin_nanf currently only supports empty string literals");
+		e = mkexpr(EXPRCONST, &typefloat, 0);
+		/* TODO: use NAN here when we can handle musl's math.h */
+		e->constant.f = strtod("nan", NULL);
+		break;
 	case BUILTININFF:
 		e = mkexpr(EXPRCONST, &typefloat, 0);
 		/* TODO: use INFINITY here when we can handle musl's math.h */
diff --git a/scope.c b/scope.c
index 00569b9..be561f5 100644
--- a/scope.c
+++ b/scope.c
@@ -24,6 +24,7 @@ scopeinit(void)
 		{"__builtin_va_end",   {.kind = DECLBUILTIN, .builtin = BUILTINVAEND}},
 		{"__builtin_offsetof", {.kind = DECLBUILTIN, .builtin = BUILTINOFFSETOF}},
 		{"__builtin_alloca",   {.kind = DECLBUILTIN, .builtin = BUILTINALLOCA}},
+		{"__builtin_nanf",     {.kind = DECLBUILTIN, .builtin = BUILTINNANF}},
 		{"__builtin_inff",     {.kind = DECLBUILTIN, .builtin = BUILTININFF}},
 	};
 	struct builtin *b;
diff --git a/tests/builtin-nanf.c b/tests/builtin-nanf.c
new file mode 100644
index 0000000..d239a46
--- /dev/null
+++ b/tests/builtin-nanf.c
@@ -0,0 +1 @@
+float x = __builtin_nanf("");
diff --git a/tests/builtin-nanf.qbe b/tests/builtin-nanf.qbe
new file mode 100644
index 0000000..5fd7ac2
--- /dev/null
+++ b/tests/builtin-nanf.qbe
@@ -0,0 +1 @@
+export data $x = align 4 { s s_nan, }
-- 
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