Replacing table of contents (TOC)-setting instructions in code with TOC predicting instructions

• US 10,713,051 B2
• Filed: 11/17/2017
• Issued: 07/14/2020
• Est. Priority Date: 09/19/2017
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gschwind, Michael K., Salapura, Valentina
• Primary Examiner(s): Chavis, John Q
• Application Number:
  US15/816,438
• Publication Number:
  US 20190087191A1
• Time in Patent Office: 970 Days
• Field of Search: 717151
• CPC Class Codes: G06F 9/3004 to perform operations on memory
• CPC Class Codes: G06F 9/30181 Instruction operation extension or modification
• CPC Class Codes: G06F 9/3832 Value prediction for operands; operand history buffers
• CPC Class Codes: G06F 9/3844 using dynamic branch prediction, e.g. using branch history tables

Abstract

Table of Contents (TOC)-setting instructions are replaced in code with TOC predicting instructions. A determination is made as to whether code includes an instruction sequence to compute a value of a pointer to a reference data structure, such as a TOC. Based on determining the code includes the instruction sequence, the instruction sequence in the code is replaced with a set instruction. The set instruction predicts the value of the pointer to the reference data structure.

Claims

1. A computer-implemented method of facilitating processing within a computing environment, the computer-implemented method comprising:

determining whether code includes an instruction sequence to compute a value of a pointer to a reference data structure;

replacing, based on determining the code includes the instruction sequence, the instruction sequence in the code with a set instruction, the set instruction predicting the value of the pointer to the reference data structure;

adding a verify instruction to the code to verify the value that was predicted; and

verifying the value using the verify instruction, the verifying including;

adding an offset obtained from the verify instruction to a first value obtained from a first location specified using the verify instruction to obtain a result;

comparing the result to a second value obtained from a second location specified using the verify instruction; and

determining a successful verification based on the comparing indicating a particular relationship between the result and the second value.

2. The computer-implemented method of claim 1, wherein the particular relationship comprises equality.

3. The computer-implemented method of claim 1, wherein the first location comprises a first register specified by the verify instruction and the second location comprises a second register specified by the verify instruction.

4. The computer-implemented method of claim 1, further comprising initiating recovery based on the comparing indicating a relationship other than the particular relationship.

5. The computer-implemented method of claim 4, further comprising loading a reference data structure pointer cache with the result based on the comparing indicating a relationship other than the particular relationship.

6. The computer-implemented method of claim 1, wherein the determining comprises scanning the code for one or more instructions that compute the value, the one or more instructions comprising an add immediate shift instruction and an add immediate instruction updating a register used for reference data structure pointers.

7. The computer-implemented method of claim 1, wherein the determining comprises scanning the code for one or more instructions that compute the value, the one or more instructions comprising a load instruction to load a register used for reference data structure pointers.

8. The computer-implemented method of claim 1, wherein the predicting comprises performing a look-up of a data structure to determine the value of the pointer.