From ddc6f6bcb04c2a37c68cf25f8630acc44cfc310b Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Wed, 30 Jun 2021 20:05:27 +0900
Subject: [PATCH] [qfcc] Un-dereference src expression early for movep

The VM has no pointer to direct reference move instruction.

Fixes #9
---
 tools/qfcc/source/statements.c  | 18 +++++++++++-------
 tools/qfcc/test/Makemodule.am   | 11 +++++++++++
 tools/qfcc/test/ptrstructcast.r | 22 ++++++++++++++++++++++
 3 files changed, 44 insertions(+), 7 deletions(-)
 create mode 100644 tools/qfcc/test/ptrstructcast.r

diff --git a/tools/qfcc/source/statements.c b/tools/qfcc/source/statements.c
index d2ae28e65..959f0f3c6 100644
--- a/tools/qfcc/source/statements.c
+++ b/tools/qfcc/source/statements.c
@@ -787,9 +787,13 @@ expr_assign_copy (sblock_t *sblock, expr_t *e, operand_t **op, operand_t *src)
 		}
 		type = st_memset;
 		if (is_indirect (dst_expr)) {
-			goto dereference_dst;
+			need_ptr = 1;
 		}
 	} else {
+		if (is_indirect (src_expr)) {
+			src_expr = expr_file_line (address_expr (src_expr, 0, 0), e);
+			need_ptr = 1;
+		}
 		if (!src) {
 			// This is the very right-hand node of a non-nil assignment chain
 			// (there may be more chains somwhere within src_expr, but they
@@ -802,15 +806,15 @@ expr_assign_copy (sblock_t *sblock, expr_t *e, operand_t **op, operand_t *src)
 		if (op) {
 			*op = src;
 		}
-		if (is_indirect (dst_expr) || is_indirect (src_expr)) {
+		if (is_indirect (dst_expr)) {
 			src = operand_address (src, src_expr);
-			goto dereference_dst;
+			need_ptr = 1;
 		}
 	}
-	if (0) {
-dereference_dst:
-		// dst_expr is a dereferenced pointer, so need to un-dereference it
-		// to get the pointer and switch to storep instructions.
+	if (need_ptr) {
+		// dst_expr and/or src_expr are dereferenced pointers, so need to
+		// un-dereference dst_expr to get the pointer and switch to movep
+		// or memsetp instructions.
 		dst_expr = expr_file_line (address_expr (dst_expr, 0, 0), e);
 		need_ptr = 1;
 	}
diff --git a/tools/qfcc/test/Makemodule.am b/tools/qfcc/test/Makemodule.am
index 54bb87dcf..15f9b9309 100644
--- a/tools/qfcc/test/Makemodule.am
+++ b/tools/qfcc/test/Makemodule.am
@@ -34,6 +34,7 @@ test_progs_dat=\
 	tools/qfcc/test/paramret.dat \
 	tools/qfcc/test/postop.dat \
 	tools/qfcc/test/ptraliasenc.dat \
+	tools/qfcc/test/ptrstructcast.dat \
 	tools/qfcc/test/quaternion.dat \
 	tools/qfcc/test/return-ivar.dat \
 	tools/qfcc/test/sendv.dat \
@@ -394,6 +395,16 @@ tools/qfcc/test/ptraliasenc.run: $(qfcc_test_run_deps)
 include $(ptraliasenc_dep) # am--include-marker
 r_depfiles_remade += $(ptraliasenc_dep)
 
+tools_qfcc_test_ptrstructcast_dat_SOURCES=tools/qfcc/test/ptrstructcast.r
+ptrstructcast_obj=$(tools_qfcc_test_ptrstructcast_dat_SOURCES:.r=.o)
+ptrstructcast_dep=$(call qcautodep,$(tools_qfcc_test_ptrstructcast_dat_SOURCES))
+tools/qfcc/test/ptrstructcast.dat$(EXEEXT): $(ptrstructcast_obj) $(QFCC_DEP)
+	$(V_QFCCLD)$(QLINK) -o $@ $(ptrstructcast_obj)
+tools/qfcc/test/ptrstructcast.run: $(qfcc_test_run_deps)
+	@$(top_srcdir)/tools/qfcc/test/build-run $@
+include $(ptrstructcast_dep) # am--include-marker
+r_depfiles_remade += $(ptrstructcast_dep)
+
 tools_qfcc_test_quaternion_dat_SOURCES=tools/qfcc/test/quaternion.r
 quaternion_obj=$(tools_qfcc_test_quaternion_dat_SOURCES:.r=.o)
 quaternion_dep=$(call qcautodep,$(tools_qfcc_test_quaternion_dat_SOURCES))
diff --git a/tools/qfcc/test/ptrstructcast.r b/tools/qfcc/test/ptrstructcast.r
new file mode 100644
index 000000000..36e560d08
--- /dev/null
+++ b/tools/qfcc/test/ptrstructcast.r
@@ -0,0 +1,22 @@
+typedef struct Point_s {
+	int         x;
+	int         y;
+} Point;
+
+typedef struct Extent_s {
+	int         width;
+	int         height;
+} Extent;
+
+int
+foo (Point p)
+{
+	Extent e = *(Extent *)&p;
+	return e.width * e.height;
+}
+
+int
+main (void)
+{
+	return foo ({ 6, 7 }) != 42;
+}