Performance tune

Performance tune and PA2 bugfix. Supporting ICC.

nemu/Makefile

@@ -16,12 +16,11 @@ include Makefile.git
 .DEFAULT_GOAL = app
 
 # Compilation flags
-CXX = icpc
+CXX ?= g++
 LD = $(CXX)
-EXTRA_FLAGS ?= -prof-use
 INCLUDES  = $(addprefix -I, $(INC_DIR))
 CFLAGS   += -O3 -MMD -Wall $(INCLUDES) -fomit-frame-pointer -std=c++17
-CFLAGS   += -no-ansi-alias -DDISABLE_MMIO -no-complex-limited-range -qopt-prefetch=2 $(EXTRA_FLAGS)
+CFLAGS   += $(EXTRA_FLAGS)
 # CFLAGS   += -DDIFF_TEST_QEMU
 
 # Source code generation before any targets.