MIPS architecture - Wikipedia All MIPS I control flow instructions are followed by a branch delay slot. Unless the branch delay slot is filled by an instruction performing useful work, an nop is substituted. MIPS I branch instructions compare the contents of a GPR (rs) against zero or another GPR … Having Fun with Branch Delay Slots – pagetable.com Abusing the load delay or branch delay on MIPS-I (and probably later chips too) is only safe if there is no way an interrupt can occur. When an interrupt occurs in a branch delay slot, the cpu subtracts 4 from the PC. However if you have a branch in a branch delay slot, then the CPU will subtract 4 from the address the second branch pointed at. MIPS Delay Slot Instructions: TotalView Reference Guide (v6.3) In addition, there is a group of "branch likely" conditional branch instructions in which the instruction in the delay slot is executed only if the branch is taken. The MIPS processors execute the jump or branch instruction and the delay slot instruction as an indivisible unit. If an exception occurs as a result of executing the delay slot
This is because: (i) returning from the subroutine to the jal instruction would be a disaster (since it would execute again, sending control back to the subroutine), and (ii) the instruction following the jal is a branch delay slot.
Pipelining: Branch Hazards • The original SPARC and MIPS processors each used a single branch delay slot to eliminate single-cycle stalls after branches. • The instruction after a conditional branch is always executed in those machines, regardless of whether the branch is taken or not! Branch delay slots - gem5 - m5 sim Since MIPS and SPARC use branch delay slots, we're faced with an interesting issue on how to implement them correctly. There are two issues: basic support for branch delay slots, and support for conditionally executed delay-slot instructions (SPARC "annulled" delay slots). Control Instructions - courses.cs.washington.edu
Quiz for Chapter 4 The Processor ... and 1 delay slot for branches. The pipeline is the typical 5-stage IF, ID, EX, MEM, WB MIPS design. ... variation in the MIPS ...
JEB MIPS Decompiler - JEB Decompiler by PNF Software Not to mention other intricacies inherent to a RISC instruction set, such as unaligned reads and writes; or counter-intuitive idioms closely tight to the MIPS architecture itself, such as the branch delay slots or seemingly opaque code blocks. A strong decompiler is a precious tool to deep dive into MIPS code efficiently. Instruction Pipelining Review: - PowerPoint PPT Presentation branch-delay slot instruction. When the branch goes as predicted, the instruction in the branch delay slot is executed normally. When the branch does not go as predicted the instruction is turned into a no-op (i.e. cancelled). Canceling branches eliminate the conditions on instruction selection in delay instruction strategies B, C Delay slot - Wikipedia
RE: [PATCH, Mips] Compact branch/delay slot optimization.
Apr 12, 2018 · The BAL instruction sets the ra register to point to the instruction after the branch delay slot, which in our case is the first NOP. But in the branch delay slot, we modify the ra register, so that when execution reaches the start of the called procedure, it gets an artificial return address. Branch delay slots - gem5 - m5 sim In MIPS, executing a branch in a branch delay slot results in UNDETERMINED behavior. Conditional delay slot instructions. Things get more complicated when the delay-slot instruction is effectively predicated on the branch direction. SPARC supports "annulled" branches in which the delay-slot instruction is not executed if the branch is not taken. CMSC 411 Computer Systems Architecture Lecture 5 Basic
Example with MIPS, Pipelining and Branch Delay Slot
Apparently MIPS is even more complex, with bits that allow the delay-slot instruction to be predicated in either ... MIPS Processor Implementation of Pipelined MIPS Processor. Sept. 24 & 26, 1997 ... MIPS architecture subset. 0 rs rt rd ...... unless instruction was in branch delay slot, in which case re-execute. Pipeline Control Hazards - Cornell Computer Science
Pipeline Control Hazards and Instruction Variations