[llvm-bugs] [Bug 37837] New: [X86] Most Intel scheduler models have strange values for integer division

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37837

            Bug ID: 37837
           Summary: [X86] Most Intel scheduler models have strange values
                    for integer division
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: llvm-dev at redking.me.uk
                CC: clement.courbet at gmail.com, craig.topper at gmail.com,
                    gchatelet at google.com, llvm-bugs at lists.llvm.org

Every model later than SandyBridge specifies integer division overrides with a
long set of uops, but interestingly don't use the divider resource at all:

e.g.

def SKXWriteResGroup264 :
SchedWriteRes<[SKXPort0,SKXPort1,SKXPort5,SKXPort6,SKXPort05,SKXPort0156]> {
  let Latency = 76;
  let NumMicroOps = 32;
  let ResourceCycles = [7,2,8,3,1,11];
}
def: InstRW<[SKXWriteResGroup264], (instregex "DIV(16|32|64)r")>;

def SKXWriteResGroup265 :
SchedWriteRes<[SKXPort0,SKXPort1,SKXPort5,SKXPort6,SKXPort06,SKXPort0156]> {
  let Latency = 102;
  let NumMicroOps = 66;
  let ResourceCycles = [4,2,4,8,14,34];
}
def: InstRW<[SKXWriteResGroup265], (instregex "IDIV(16|32|64)r")>;

I think the default scheduler classes are being mostly/completely ignored:

defm : SKXWriteResPair<WriteDiv8,   [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;
defm : SKXWriteResPair<WriteDiv16,  [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;
defm : SKXWriteResPair<WriteDiv32,  [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;
defm : SKXWriteResPair<WriteDiv64,  [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;
defm : SKXWriteResPair<WriteIDiv8,  [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;
defm : SKXWriteResPair<WriteIDiv16, [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;
defm : SKXWriteResPair<WriteIDiv32, [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;
defm : SKXWriteResPair<WriteIDiv64, [SKXPort0, SKXDivider], 25, [1,10], 1, 4>;

So, should the SKXDivider be specified in these overrides? And can those values
be used in the existing WriteDiv/WriteIDiv standard classes and the overrides
removed?

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