[IMPALA-3637] Merge codegen constant replacement mechanisms

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Later
• Affects Version/s: Impala 2.6.0
• Component/s: Backend
• Labels: codegen
• Target Version: Product Backlog
• Assignee: Unassigned
• Reporter: Tim Armstrong
• Created: 27/May/16 19:08
• Updated: 02/Nov/20 19:22
• Resolved: 02/Nov/20 19:22

Description

We currently have two similar way to replace constants in codegen'd code: Expr::GetConstant() and LlvmCodeGen::ReplaceCallSitesWithBoolConst(). We should merge them so that we have a single mechanism with the functionality of both.

E.g.
A version that takes a map where the key is a symbol and the value is a constant, or a vector of constants:

ReplaceCallSitesWithConstants(Function* map, <string, ConstantInfo>*)

We could then avoid the expensive Expr::GetConstant() call on the interpreted path.

Issue Links

• blocks: IMPALA-4785 Constant from GetIntermediateType() are not propagated when codegen'ing aggregate functions
• blocks: IMPALA-3636 Regression in DecimalOperators::EQ with codegen disabled