Re: [PATCH 3/4] sparse, llvm: base load/store address type on insn_symbol_type()

[Xi Wang <xi.wang@gmail.com>]

On 05/18/2013 01:52 PM, Jonathan Neuschäfer wrote:
>   	/* convert address back to pointer */
> -	addr = LLVMBuildIntToPtr(fn->builder, addr_i,
> -				 LLVMTypeOf(src_p), "addr");
> +	addr = LLVMBuildIntToPtr(fn->builder, addr_i, addr_type, "addr");

Actually, we shouldn't convert pointers to integers in the first place.
This effectively disables pointer analysis and future optimizations.

A better way is to use LLVM's GEP for pointer arithmetic, by converting
pointers to `char *', rather than integers.

See more examples here:
http://www.spinics.net/lists/linux-sparse/msg02768.html

Jonathan, how about this version using `char *' based on your patchset?

diff --git a/sparse-llvm.c b/sparse-llvm.c
index 00ace6e..a01c4b7 100644
--- a/sparse-llvm.c
+++ b/sparse-llvm.c
@@ -541,24 +541,47 @@ static void output_op_ret(struct function *fn, struct instruction *insn)
 		LLVMBuildRetVoid(fn->builder);
 }
 
-static void output_op_load(struct function *fn, struct instruction *insn)
+static LLVMValueRef calc_gep(LLVMBuilderRef builder, LLVMValueRef base, LLVMValueRef off)
+{
+	LLVMTypeRef type = LLVMTypeOf(base);
+	unsigned int as = LLVMGetPointerAddressSpace(type);
+	LLVMTypeRef bytep = LLVMPointerType(LLVMInt8Type(), as);
+	LLVMValueRef addr;
+
+	/* convert base to char* type */
+	base = LLVMBuildPointerCast(builder, base, bytep, "");
+	/* addr = base + off */
+	addr = LLVMBuildInBoundsGEP(builder, base, &off, 1, "");
+	/* convert base back to the actual pointer type */
+	addr = LLVMBuildPointerCast(builder, addr, type, "");
+	return addr;
+}
+
+static LLVMValueRef calc_memop_addr(struct function *fn, struct instruction *insn)
 {
-	LLVMTypeRef int_type;
-	LLVMValueRef src_p, src_i, ofs_i, addr_i, addr, target;
+	LLVMTypeRef addr_type, int_type;
+	LLVMValueRef src, base, off, addr;
+	unsigned int as;
+
+	src = pseudo_to_value(fn, insn, insn->src);
+	as = LLVMGetPointerAddressSpace(LLVMTypeOf(src));
+	addr_type = LLVMPointerType(insn_symbol_type(fn->module, insn), as);
+	base = LLVMBuildPointerCast(fn->builder, src, addr_type, "");
 
 	/* int type large enough to hold a pointer */
 	int_type = LLVMIntType(bits_in_pointer);
+	off = LLVMConstInt(int_type, insn->offset, 0);
+
+	addr = calc_gep(fn->builder, base, off);
+	return addr;
+}
 
-	/* convert to integer, add src + offset */
-	src_p = pseudo_to_value(fn, insn, insn->src);
-	src_i = LLVMBuildPtrToInt(fn->builder, src_p, int_type, "src_i");
 
-	ofs_i = LLVMConstInt(int_type, insn->offset, 0);
-	addr_i = LLVMBuildAdd(fn->builder, src_i, ofs_i, "addr_i");
+static void output_op_load(struct function *fn, struct instruction *insn)
+{
+	LLVMValueRef addr, target;
 
-	/* convert address back to pointer */
-	addr = LLVMBuildIntToPtr(fn->builder, addr_i,
-				 LLVMTypeOf(src_p), "addr");
+	addr = calc_memop_addr(fn, insn);
 
 	/* perform load */
 	target = LLVMBuildLoad(fn->builder, addr, "load_target");
@@ -568,22 +591,9 @@ static void output_op_load(struct function *fn, struct instruction *insn)
 
 static void output_op_store(struct function *fn, struct instruction *insn)
 {
-	LLVMTypeRef int_type;
-	LLVMValueRef src_p, src_i, ofs_i, addr_i, addr, target, target_in;
-
-	/* int type large enough to hold a pointer */
-	int_type = LLVMIntType(bits_in_pointer);
-
-	/* convert to integer, add src + offset */
-	src_p = pseudo_to_value(fn, insn, insn->src);
-	src_i = LLVMBuildPtrToInt(fn->builder, src_p, int_type, "src_i");
-
-	ofs_i = LLVMConstInt(int_type, insn->offset, 0);
-	addr_i = LLVMBuildAdd(fn->builder, src_i, ofs_i, "addr_i");
+	LLVMValueRef addr, target, target_in;
 
-	/* convert address back to pointer */
-	addr = LLVMBuildIntToPtr(fn->builder, addr_i,
-				 LLVMPointerType(int_type, 0), "addr");
+	addr = calc_memop_addr(fn, insn);
 
 	target_in = pseudo_to_value(fn, insn, insn->target);
 
diff --git a/validation/backend/store-type.c b/validation/backend/store-type.c
new file mode 100644
index 0000000..9e2ce73
--- /dev/null
+++ b/validation/backend/store-type.c
@@ -0,0 +1,12 @@
+struct foo;
+static struct foo *var;
+
+static void set(struct foo *f)
+{
+       var = f;
+}
+
+/*
+ * check-name: Type of stored objects
+ * check-command: ./sparsec -c $file -o tmp.o
+ */
diff --git a/validation/backend/struct-access.c b/validation/backend/struct-access.c
new file mode 100644
index 0000000..884b470
--- /dev/null
+++ b/validation/backend/struct-access.c
@@ -0,0 +1,28 @@
+struct st {
+	int i, *d;
+};
+
+static int load_i(struct st *st)
+{
+	return st->i;
+}
+
+static void store_i(struct st *st, int i)
+{
+	st->i = i;
+}
+
+static int *load_d(struct st *st)
+{
+	return st->d;
+}
+
+static void store_d(struct st *st, int *d)
+{
+	st->d = d;
+}
+
+/*
+ * check-name: struct access code generation
+ * check-command: ./sparsec -c $file -o tmp.o
+ */
--
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