Implement a temporary allocator

3 files changed, 80 insertions, 11 deletions

diff --git a/src/alloc.h b/src/alloc.h
index 2c67fb7..79d7c0b 100644
--- a/src/alloc.h
+++ b/src/alloc.h
@@ -7,12 +7,26 @@
 #include "common.h"
 
 typedef struct _arena *arena_t;
+typedef struct {
+	void *p;
+	size_t sz;
+} scratch_t;
 
 /* Allocate a buffer of NMEMB elements of size SIZE.  If PTR is non-null then
    reallocate the buffer it points to.  Aborts on out-of-memory or overflow. */
 void *bufalloc(void *ptr, size_t nmemb, size_t size)
 	__attribute__((returns_nonnull, warn_unused_result, alloc_size(2, 3)));
 
+/* Alloc a buffer of NMEMB elements of size SIZE for one time use.  Each
+   time this function is invoked previous allocations are overwritten. */
+void *tmpalloc(scratch_t *s, size_t nmemb, size_t size)
+	__attribute__((returns_nonnull, warn_unused_result, nonnull,
+                   alloc_size(2, 3)));
+
+/* Reallocate all memory associated with S */
+void tmpfree(scratch_t *s)
+	__attribute__((nonnull));
+
 /* Allocate a buffer of NMEMB elements of size SIZE with alignment ALIGN using
    the arena-allocator A. */
 void *arena_alloc(arena_t *a, size_t nmemb, size_t size, size_t align)
diff --git a/src/codegen.c b/src/codegen.c
index 08f5ab5..1431693 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -21,6 +21,7 @@
    have easy access to everything */
 struct cgctx {
 	arena_t a;
+	scratch_t *s;
 	LLVMContextRef ctx;
 	LLVMModuleRef mod;
 	LLVMBuilderRef bob;
@@ -43,6 +44,7 @@ codegen(const char *file, mpq_t *folds, scope_t *scps, type_t *types,
 
 	struct cgctx ctx;
 	ctx.a = NULL;
+	ctx.s = &(scratch_t){0};
 	ctx.namespace.p = NULL;
 	ctx.ctx = LLVMContextCreate();
 	ctx.mod = LLVMModuleCreateWithNameInContext("oryx", ctx.ctx);
@@ -54,6 +56,7 @@ codegen(const char *file, mpq_t *folds, scope_t *scps, type_t *types,
 	codegenast(ctx, folds, types, ast, aux, toks);
 
 	arena_free(&ctx.a);
+	tmpfree(ctx.s);
 
 	LLVMDisposeBuilder(ctx.bob);
 
@@ -188,12 +191,9 @@ codegendecl(struct cgctx ctx, mpq_t *folds, type_t *types, ast_t ast, aux_t aux,
 
 		strview_t sv = toks.strs[ast.lexemes[i]];
 		/* TODO: Namespace the name */
-		/* TODO: Temporary allocator */
-		char *name = bufalloc(NULL, sv.len + 1, 1);
+		char *name = tmpalloc(ctx.s, sv.len + 1, 1);
 		svtocstr(name, sv);
-		i = codegenfunc(ctx, folds, types, ast, aux, toks, p.rhs, name);
-		free(name);
-		return i;
+		return codegenfunc(ctx, folds, types, ast, aux, toks, p.rhs, name);
 	}
 
 	assert(ast.kinds[i] == ASTDECL);
@@ -201,11 +201,9 @@ codegendecl(struct cgctx ctx, mpq_t *folds, type_t *types, ast_t ast, aux_t aux,
 	if (!types[i].isfloat && aux.buf[p.lhs].decl.isstatic) {
 		strview_t sv = toks.strs[ast.lexemes[i]];
 		/* TODO: Namespace the name */
-		/* TODO: Temporary allocator */
-		char *name = bufalloc(NULL, sv.len + 1, 1);
+		char *name = tmpalloc(ctx.s, sv.len + 1, 1);
 		LLVMTypeRef t = type2llvm(ctx, types[i]);
 		LLVMValueRef globl = LLVMAddGlobal(ctx.mod, t, svtocstr(name, sv));
-		free(name);
 
 		LLVMValueRef v;
 		i = codegentypedexpr(ctx, folds, types, ast, aux, toks, p.rhs, types[i], &v);
@@ -216,12 +214,10 @@ codegendecl(struct cgctx ctx, mpq_t *folds, type_t *types, ast_t ast, aux_t aux,
 	if (!types[i].isfloat /* && !aux.buf[p.lhs].decl.isstatic */) {
 		strview_t sv = toks.strs[ast.lexemes[i]];
 		/* TODO: Namespace the name */
-		/* TODO: Temporary allocator */
-		char *name = bufalloc(NULL, sv.len + 1, 1);
+		char *name = tmpalloc(ctx.s, sv.len + 1, 1);
 		LLVMTypeRef t = type2llvm(ctx, types[i]);
 		LLVMValueRef var, val;
 		var = LLVMBuildAlloca(ctx.bob, t, svtocstr(name, sv));
-		free(name);
 		i = codegentypedexpr(ctx, folds, types, ast, aux, toks, p.rhs, types[i], &val);
 		LLVMBuildStore(ctx.bob, val, var);
 		return i;
diff --git a/src/scratch.c b/src/scratch.c
new file mode 100644
index 0000000..ae48ff6
--- /dev/null
+++ b/src/scratch.c
@@ -0,0 +1,59 @@
+#include <sys/mman.h>
+
+#include <errno.h>
+#include <stdint.h>
+
+#include "alloc.h"
+#include "common.h"
+#include "errors.h"
+
+/* TODO: Support malloc() backend for systems without MAP_ANON */
+#ifndef MAP_ANON
+#	error "System not supported (missing MAP_ANON)"
+#endif
+
+#if DEBUG
+#	define TMP_DFLT_BUFSZ (8)
+#else /* Probably super overkill, but that’s fine */
+#	define TMP_DFLT_BUFSZ (1 * 1024)
+#endif
+
+#define MAX(x, y) ((x) > (y) ? (x) : (y))
+
+void *
+tmpalloc(scratch_t *s, size_t nmemb, size_t size)
+{
+	if (unlikely(size > SIZE_MAX / nmemb)) {
+		errno = ENOMEM;
+		err("%s:", __func__);
+	}
+	size *= nmemb;
+
+	if (s->p == NULL) {
+#if !__linux__
+do_mmap:
+#endif
+		s->sz = MAX(size, TMP_DFLT_BUFSZ);
+		s->p = mmap(s->p, s->sz, PROT_READ | PROT_WRITE,
+		            MAP_PRIVATE | MAP_ANON, -1, 0);
+		if (s->p == MAP_FAILED)
+			err("mmap:");
+	} else if (size > s->sz) {
+#if __linux__
+		if ((s->p = mremap(s->p, s->sz, size, MREMAP_MAYMOVE)) == MAP_FAILED)
+			err("mremap:");
+		s->sz = size;
+#else
+		munmap(s->p, s->sz);
+		goto do_mmap;
+#endif
+	}
+
+	return s->p;
+}
+
+void
+tmpfree(scratch_t *s)
+{
+	munmap(s->p, s->sz);
+}