[llvm-exegesis] Improve Register Setup.

Summary:
Added function to set a register to a particular value + tests.
Add EFLAGS test, use new setRegTo instead of setRegToConstant.

Reviewers: courbet, javed.absar

Subscribers: mgorny, tschuett, llvm-commits

Differential Revision: https://reviews.llvm.org/D51856

llvm-svn: 342466
diff --git a/llvm/tools/llvm-exegesis/lib/SnippetGenerator.h b/llvm/tools/llvm-exegesis/lib/SnippetGenerator.h
index ced8ebc..2a412ba 100644
--- a/llvm/tools/llvm-exegesis/lib/SnippetGenerator.h
+++ b/llvm/tools/llvm-exegesis/lib/SnippetGenerator.h
@@ -48,8 +48,8 @@
   generateConfigurations(unsigned Opcode) const;
 
   // Given a snippet, computes which registers the setup code needs to define.
-  std::vector<unsigned>
-  computeRegsToDef(const std::vector<InstructionBuilder> &Snippet) const;
+  std::vector<RegisterValue> computeRegisterInitialValues(
+      const std::vector<InstructionBuilder> &Snippet) const;
 
 protected:
   const LLVMState &State;