Reduce one layer of decoding for binary operations in bitcode reading.

Removes the need to call function llvm::DecodeBinaryOp. In turn, this removes
the need for enum type llvm::Instruction::BinaryOps, llvm::Type.isFPOrFPVectorTy, and one call to llvm::convertToLLVMType.

BUG= None
R=jvoung@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/788283002
diff --git a/tests_lit/llvm2ice_tests/mangle.ll b/tests_lit/llvm2ice_tests/mangle.ll
index 5bd0a55..2d4384e 100644
--- a/tests_lit/llvm2ice_tests/mangle.ll
+++ b/tests_lit/llvm2ice_tests/mangle.ll
@@ -1,6 +1,7 @@
 ; Tests the Subzero "name mangling" when using the "llvm2ice --prefix"
 ; option.  Also does a quick smoke test of -ffunction-sections.
 
+; REQUIRES: allow_dump
 ; RUN: %p2i -i %s --args --verbose none -ffunction-sections | FileCheck %s
 ; TODO(stichnot): The following line causes this test to fail.
 ; RUIN: %p2i -i %s --args --verbose none \