From b6093e07282c4ac8cc734301f279377eebb05954 Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Sun, 23 Jan 2022 01:31:50 +0900
Subject: [PATCH] [qfcc] Add failing test for lost var use

Storing a variable into a dereference pointer (*p = x) is not marking
the variable as used (due to a mistake while converting to Ruamoko
statement format) resulting in assignments to that variable being
dropped due to it being a dead assignment as the assignment to the
variable and the storing need to be in separate basic blocks (thus the
call in the test, though an if would have worked, I think) for the bug
to trigger.
---
 tools/qfcc/test/Makemodule.am | 11 +++++++++++
 tools/qfcc/test/lost-use.r    | 29 +++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+)
 create mode 100644 tools/qfcc/test/lost-use.r

diff --git a/tools/qfcc/test/Makemodule.am b/tools/qfcc/test/Makemodule.am
index 1f310048a..88b9e8480 100644
--- a/tools/qfcc/test/Makemodule.am
+++ b/tools/qfcc/test/Makemodule.am
@@ -31,6 +31,7 @@ test_progs_dat=\
 	tools/qfcc/test/infloop.dat \
 	tools/qfcc/test/ivar-struct-return.dat \
 	tools/qfcc/test/link_order.dat \
+	tools/qfcc/test/lost-use.dat \
 	tools/qfcc/test/methodparams.dat \
 	tools/qfcc/test/modulo.dat \
 	tools/qfcc/test/nilparamret.dat \
@@ -386,6 +387,16 @@ tools/qfcc/test/link_order.run: $(qfcc_test_run_deps)
 include $(link_order_dep) # am--include-marker
 r_depfiles_remade += $(link_order_dep)
 
+tools_qfcc_test_lost_use_dat_SOURCES=tools/qfcc/test/lost-use.r
+lost_use_obj=$(tools_qfcc_test_lost_use_dat_SOURCES:.r=.o)
+lost_use_dep=$(call qcautodep,$(tools_qfcc_test_lost_use_dat_SOURCES))
+tools/qfcc/test/lost-use.dat$(EXEEXT): $(lost_use_obj) $(QFCC_DEP)
+	$(V_QFCCLD)$(QLINK) -o $@ $(lost_use_obj)
+tools/qfcc/test/lost-use.run: $(qfcc_test_run_deps)
+	@$(top_srcdir)/tools/qfcc/test/build-run $@
+include $(lost_use_dep) # am--include-marker
+r_depfiles_remade += $(lost_use_dep)
+
 tools_qfcc_test_methodparams_dat_SOURCES=tools/qfcc/test/methodparams.r
 methodparams_obj=$(tools_qfcc_test_methodparams_dat_SOURCES:.r=.o)
 methodparams_dep=$(call qcautodep,$(tools_qfcc_test_methodparams_dat_SOURCES))
diff --git a/tools/qfcc/test/lost-use.r b/tools/qfcc/test/lost-use.r
new file mode 100644
index 000000000..dc9d79142
--- /dev/null
+++ b/tools/qfcc/test/lost-use.r
@@ -0,0 +1,29 @@
+void printf (string fmt, ...) = #0;
+int getval(void)
+{
+	return 42;
+}
+
+void magic (void)
+{
+}
+
+void storeval (int *p)
+{
+	int x = getval ();
+	magic ();
+	*p = x;
+}
+
+int val;
+
+int
+main(void)
+{
+	storeval (&val);
+	if (val != 42) {
+		printf ("val is dead: %d\n", val);
+		return 1;
+	}
+	return 0;
+}