From 8cff9743c0c184ced21459efbe0bb0b6b7a65d31 Mon Sep 17 00:00:00 2001
From: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Date: Mon, 28 Feb 2022 08:25:00 +0100
Subject: [PATCH] seminaries/qtrvsim: add ffs-as-log2, the fisrt motivation
example from lecture.
Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
---
seminaries/qtrvsim/ffs-as-log2/.gitignore | 3 +
seminaries/qtrvsim/ffs-as-log2/Makefile | 77 ++++++++++++++++++++
seminaries/qtrvsim/ffs-as-log2/ffs-as-log2.S | 19 +++++
3 files changed, 99 insertions(+)
create mode 100644 seminaries/qtrvsim/ffs-as-log2/.gitignore
create mode 100644 seminaries/qtrvsim/ffs-as-log2/Makefile
create mode 100644 seminaries/qtrvsim/ffs-as-log2/ffs-as-log2.S
diff --git a/seminaries/qtrvsim/ffs-as-log2/.gitignore b/seminaries/qtrvsim/ffs-as-log2/.gitignore
new file mode 100644
index 0000000..591297f
--- /dev/null
+++ b/seminaries/qtrvsim/ffs-as-log2/.gitignore
@@ -0,0 +1,3 @@
+*.o
+depend
+change_me
diff --git a/seminaries/qtrvsim/ffs-as-log2/Makefile b/seminaries/qtrvsim/ffs-as-log2/Makefile
new file mode 100644
index 0000000..0a9adde
--- /dev/null
+++ b/seminaries/qtrvsim/ffs-as-log2/Makefile
@@ -0,0 +1,77 @@
+ARCH=riscv64-unknown-elf
+
+SOURCES = ffs-as-log2.S
+TARGET_EXE = ffs-as-log2
+
+CC=$(ARCH)-gcc
+CXX=$(ARCH)-g++
+AS=$(ARCH)-as
+LD=$(ARCH)-ld
+OBJCOPY=$(ARCH)-objcopy
+
+ARCHFLAGS += -mabi=ilp32
+ARCHFLAGS += -march=rv32i
+ARCHFLAGS += -fno-lto
+
+CFLAGS += -ggdb -Os -Wall
+CXXFLAGS+= -ggdb -Os -Wall
+AFLAGS += -ggdb
+LDFLAGS += -ggdb
+LDFLAGS += -nostartfiles
+LDFLAGS += -nostdlib
+LDFLAGS += -static
+#LDFLAGS += -specs=/opt/musl/riscv64-linux-gnu/lib/musl-gcc.specs
+
+CFLAGS += $(ARCHFLAGS)
+CXXFLAGS+= $(ARCHFLAGS)
+AFLAGS += $(ARCHFLAGS)
+LDFLAGS += $(ARCHFLAGS)
+
+OBJECTS += $(filter %.o,$(SOURCES:%.S=%.o))
+OBJECTS += $(filter %.o,$(SOURCES:%.c=%.o))
+OBJECTS += $(filter %.o,$(SOURCES:%.cpp=%.o))
+
+all : default
+
+.PHONY : default clean dep all
+
+%.o:%.S
+ $(CC) -D__ASSEMBLY__ $(AFLAGS) -c $< -o $@
+
+%.o:%.c
+ $(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $@
+
+%.o:%.cpp
+ $(CXX) $(CXXFLAGS) $(CPPFLAGS) -c $<
+
+%.s:%.c
+ $(CC) $(CFLAGS) $(CPPFLAGS) -S $< -o $@
+
+default : $(TARGET_EXE)
+
+$(TARGET_EXE) : $(OBJECTS)
+ $(CC) $(LDFLAGS) $^ -o $@
+
+dep: depend
+
+depend: $(SOURCES) $(glob *.h)
+ echo '# autogenerated dependencies' > depend
+ifneq ($(filter %.S,$(SOURCES)),)
+ $(CC) -D__ASSEMBLY__ $(AFLAGS) -w -E -M $(filter %.S,$(SOURCES)) \
+ >> depend
+endif
+ifneq ($(filter %.c,$(SOURCES)),)
+ $(CC) $(CFLAGS) $(CPPFLAGS) -w -E -M $(filter %.c,$(SOURCES)) \
+ >> depend
+endif
+ifneq ($(filter %.cpp,$(SOURCES)),)
+ $(CXX) $(CXXFLAGS) $(CPPFLAGS) -w -E -M $(filter %.cpp,$(SOURCES)) \
+ >> depend
+endif
+
+clean:
+ rm -f *.o *.a $(OBJECTS) $(TARGET_EXE) depend
+
+#mips-elf-objdump --source -M no-aliases,reg-names=numeric qtmips_binrep
+
+-include depend
diff --git a/seminaries/qtrvsim/ffs-as-log2/ffs-as-log2.S b/seminaries/qtrvsim/ffs-as-log2/ffs-as-log2.S
new file mode 100644
index 0000000..ed80360
--- /dev/null
+++ b/seminaries/qtrvsim/ffs-as-log2/ffs-as-log2.S
@@ -0,0 +1,19 @@
+// ffs as log2(x)
+.globl _start
+.globl __start
+.option norelax
+.text
+
+__start:
+_start:
+ addi a0, zero, 157 // int x = 157;
+ addi t1, zero, -1 // int y = 0;
+ beq a0, zero, done // while(x != 0)
+loop: // {
+ srli a0, a0, 1 // x = x / 2;
+ addi t1, t1, 1 // y = y + 1;
+ bne a0, zero, loop //}
+done:
+ addi a0, t1, 0
+finish: ebreak
+ beq zero, zero, finish
--
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