Initial skeleton of Subzero.

This includes just enough code to build the high-level ICE IR and dump it back out again.  There is a script szdiff.py that does a fuzzy diff of the input and output for verification.  See the comment in szdiff.py for a description of the fuzziness.

Building llvm2ice requires LLVM headers, libs, and tools (e.g. FileCheck) to be present.  These default to something like llvm_i686_linux_work/Release+Asserts/ based on the checked-out and built pnacl-llvm code; I'll try to figure out how to more automatically detect the build configuration.

"make check" runs the lit tests.

This CL has under 2000 lines of "interesting" Ice*.{h,cpp} code, plus 600 lines of llvm2ice.cpp driver code, and the rest is tests.

Here is the high-level mapping of source files to functionality:

IceDefs.h, IceTypes.h, IceTypes.cpp:
Commonly used types and utilities.

IceCfg.h, IceCfg.cpp:
Operations at the function level.

IceCfgNode.h, IceCfgNode.cpp:
Operations on basic blocks (nodes).

IceInst.h, IceInst.cpp:
Operations on instructions.

IceOperand.h, IceOperand.cpp:
Operations on operands, such as stack locations, physical registers, and constants.

BUG= none
R=jfb@chromium.org

Review URL: https://codereview.chromium.org/205613002

tests_lit/llvm2ice_tests/arithmetic-chain.ll

diff --git a/tests_lit/llvm2ice_tests/arithmetic-chain.ll b/tests_lit/llvm2ice_tests/arithmetic-chain.ll
new file mode 100644
index 0000000..3ca1ad0
--- /dev/null
+++ b/tests_lit/llvm2ice_tests/arithmetic-chain.ll
@@ -0,0 +1,24 @@
+; RUIN: %llvm2ice -verbose inst %s | FileCheck %s
+; RUIN: %llvm2ice --verbose none %s | FileCheck --check-prefix=ERRORS %s
+; RUN: %szdiff --llvm2ice=%llvm2ice %s | FileCheck --check-prefix=DUMP %s
+
+define i64 @arithmetic_chain(i64 %foo, i64 %bar) {
+entry:
+  %r1 = add i64 %foo, %bar
+  %r2 = add i64 %foo, %r1
+  %r3 = mul i64 %bar, %r1
+  %r4 = shl i64 %r3, %r2
+  %r5 = add i64 %r4, 8
+  ret i64 %r5
+
+; CHECK:      entry:
+; CHECK-NEXT:  %r1 = add i64 %foo, %bar
+; CHECK-NEXT:  %r2 = add i64 %foo, %r1
+; CHECK-NEXT:  %r3 = mul i64 %bar, %r1
+; CHECK-NEXT:  %r4 = shl i64 %r3, %r2
+; CHECK-NEXT:  %r5 = add i64 %r4, 8
+; CHECK-NEXT:  ret i64 %r5
+}
+
+; ERRORS-NOT: ICE translation error
+; DUMP-NOT: SZ