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Fix temporal code motion #7959

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Fix temporal code motion #7959

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4311384
[LLHD] Fix llhd-temporal-code-motion pass
AndreyVV-100 Dec 6, 2024
0b5dc8f
Small fixes after review.
AndreyVV-100 Dec 6, 2024
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40 changes: 40 additions & 0 deletions lib/Dialect/LLHD/Transforms/TemporalCodeMotionPass.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,45 @@ getBranchDecisionsFromDominatorToTarget(OpBuilder &builder, Block *driveBlock,
return mem[driveBlock];
}

/// Move 'llhd.drv' op '$value' definition (if it present) and it's dependencies
/// by lookup in current block. It's expected that other dependencies are placed
/// before 'moveBefore'. It's almost 'true' due to 'hw.constant' and 'llhd.sig'
/// ops are placed before 'llhd.process'.
static void moveValueDependencies(llhd::DrvOp drvOp, Operation *moveBefore) {
auto *drvBlock = drvOp->getBlock();
auto value = drvOp.getValue();
if (value.getParentBlock() != drvBlock || !value.getDefiningOp())
return;

llvm::SmallVector<Operation *> moveSet;
moveSet.push_back(value.getDefiningOp());

// Algorithm is finite due to recursive dependencies can't exist
// in single linear block
for (unsigned currOp = 0; currOp != moveSet.size(); currOp++) {
for (auto arg : moveSet[currOp]->getOperands()) {
if (arg.getParentBlock() == drvBlock) {
auto *op = arg.getDefiningOp();
assert(op && "Using block argument as llhd.drv value is unexpected");
Comment on lines +109 to +110
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This assumes that passes like block-argument-to-mux are called beforehand. But the pass shouldn't crash if that's not the case, i.e., this should fail with a proper error message or be supported.

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@AndreyVV-100 AndreyVV-100 Dec 10, 2024 •
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I was thinking about merging

Can I try to implement this? Should old passes be deprecated or removed? Should corresponding files be merged or can we just call passes successively in third file?


// Perform a search and removal of previously found dependencies
// on the same reference is performed for later placement.
// Later placement in the set leads to earlier placement in
// the resulting code, which will help eliminate conflicts.
if (auto *olderOpUse = std::find(moveSet.begin(), moveSet.end(), op);
olderOpUse != moveSet.end())
*olderOpUse = nullptr;
moveSet.push_back(op);
}
}
}

auto reversedRange = llvm::reverse(moveSet);
for (auto *op :
llvm::make_filter_range(reversedRange, [](Operation *op) { return op; }))
op->moveBefore(moveBefore);
}

/// More a 'llhd.drv' operation before the 'moveBefore' operation by adjusting
/// the 'enable' operand.
static void moveDriveOpBefore(llhd::DrvOp drvOp, Block *dominator,
Expand All @@ -107,6 +146,7 @@ static void moveDriveOpBefore(llhd::DrvOp drvOp, Block *dominator,
finalValue);

drvOp.getEnableMutable().assign(finalValue);
moveValueDependencies(drvOp, moveBefore);
drvOp->moveBefore(moveBefore);
}

Expand Down
114 changes: 88 additions & 26 deletions test/Dialect/LLHD/Transforms/temporal-code-motion.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -52,21 +52,21 @@ hw.module @basic(in %cond: i1) {
llhd.wait (%prb_k, %prb_c, %prb_e, %prb_h, %prb_d, %prb_f, %prb_g : i5, i1, i1, i4, i1, i1, i4), ^bb2
// CHECK: ^[[BB2]]:
^bb2:
// CHECK: [[V14:%.+]] = llhd.prb %k
// CHECK: [[V15:%.+]] = llhd.prb %c
// CHECK: [[V16:%.+]] = llhd.prb %e
// CHECK: [[V17:%.+]] = llhd.prb %h
// CHECK: [[V18:%.+]] = comb.concat %false{{.*}}, [[V17]] : i1, i4
// CHECK: [[V19:%.+]] = llhd.prb %d
// CHECK: [[V20:%.+]] = llhd.prb %f
// CHECK: [[V21:%.+]] = llhd.prb %k
// CHECK: [[V22:%.+]] = llhd.prb %g
// CHECK: [[V23:%.+]] = comb.concat %false{{.*}}, [[V22]] : i1, i4
// CHECK: [[V24:%.+]] = comb.sub [[V21]], [[V23]] : i5
// CHECK: [[V25:%.+]] = llhd.prb %k
// CHECK: [[V26:%.+]] = llhd.prb %g
// CHECK: [[V27:%.+]] = comb.concat %false{{.*}}, [[V26]] : i1, i4
// CHECK: [[V28:%.+]] = comb.add [[V25]], [[V27]] : i5
// CHECK: [[V14:%.+]] = llhd.prb %c
// CHECK: [[V15:%.+]] = llhd.prb %e
// CHECK: [[V16:%.+]] = llhd.prb %h
// CHECK: [[V17:%.+]] = comb.concat %false{{.*}}, [[V16]] : i1, i4
// CHECK: [[V18:%.+]] = llhd.prb %d
// CHECK: [[V19:%.+]] = llhd.prb %f
// CHECK: [[V20:%.+]] = llhd.prb %k
// CHECK: [[V21:%.+]] = llhd.prb %g
// CHECK: [[V22:%.+]] = comb.concat %false{{.*}}, [[V21]] : i1, i4
// CHECK: [[V23:%.+]] = comb.sub [[V20]], [[V22]] : i5
// CHECK: [[V24:%.+]] = llhd.prb %k
// CHECK: [[V25:%.+]] = llhd.prb %g
// CHECK: [[V26:%.+]] = comb.concat %false{{.*}}, [[V25]] : i1, i4
// CHECK: [[V27:%.+]] = comb.add [[V24]], [[V26]] : i5
// CHECK: [[V28:%.+]] = llhd.prb %k
%25 = llhd.prb %k : !hw.inout<i5>
llhd.drv %k, %25 after %1 : !hw.inout<i5>
%26 = llhd.prb %c : !hw.inout<i1>
Expand Down Expand Up @@ -102,33 +102,33 @@ hw.module @basic(in %cond: i1) {
^bb9:
llhd.drv %o, %39 after %1 : !hw.inout<i5>
cf.br ^bb1
// CHECK: llhd.drv %k, [[V14]] after [[V1]] if %true{{.*}} : !hw.inout<i5>
// CHECK: llhd.drv %k, [[V28]] after [[V1]] if %true{{.*}} : !hw.inout<i5>

// CHECK: [[V29:%.+]] = comb.and %true{{.*}}, [[V15]] : i1
// CHECK: [[V29:%.+]] = comb.and %true{{.*}}, [[V14]] : i1
// CHECK: [[V30:%.+]] = comb.or %false{{.*}}, [[V29]] : i1
// CHECK: [[V31:%.+]] = comb.and %cond, [[V30]] : i1
// CHECK: llhd.drv %l, %c0_i5 after [[V1]] if [[V31]] : !hw.inout<i5>

// CHECK: [[V33:%.+]] = comb.xor [[V15]], %true{{.*}} : i1
// CHECK: [[V33:%.+]] = comb.xor [[V14]], %true{{.*}} : i1
// CHECK: [[V34:%.+]] = comb.and %true{{.*}}, [[V33]] : i1
// CHECK: [[V35:%.+]] = comb.or %false{{.*}}, [[V34]] : i1
// CHECK: [[V36:%.+]] = comb.and [[V35]], [[V16]] : i1
// CHECK: [[V36:%.+]] = comb.and [[V35]], [[V15]] : i1
// CHECK: [[V37:%.+]] = comb.or %false{{.*}}, [[V36]] : i1
// CHECK: llhd.drv %m, [[V18]] after [[V1]] if [[V37]] : !hw.inout<i5>
// CHECK: llhd.drv %m, [[V17]] after [[V1]] if [[V37]] : !hw.inout<i5>

// CHECK: [[V40:%.+]] = comb.xor [[V16]], %true{{.*}} : i1
// CHECK: [[V40:%.+]] = comb.xor [[V15]], %true{{.*}} : i1
// CHECK: [[V41:%.+]] = comb.and [[V35]], [[V40]] : i1
// CHECK: [[V42:%.+]] = comb.or %false{{.*}}, [[V41]] : i1
// CHECK: [[V43:%.+]] = comb.and [[V42]], [[V19]] : i1
// CHECK: [[V43:%.+]] = comb.and [[V42]], [[V18]] : i1
// CHECK: [[V44:%.+]] = comb.or %false{{.*}}, [[V43]] : i1
// CHECK: [[V45:%.+]] = comb.and [[V44]], [[V20]] : i1
// CHECK: [[V45:%.+]] = comb.and [[V44]], [[V19]] : i1
// CHECK: [[V46:%.+]] = comb.or %false{{.*}}, [[V45]] : i1
// CHECK: llhd.drv %n, [[V24]] after [[V1]] if [[V46]] : !hw.inout<i5>
// CHECK: llhd.drv %n, [[V23]] after [[V1]] if [[V46]] : !hw.inout<i5>

// CHECK: [[V49:%.+]] = comb.xor [[V20]], %true{{.*}} : i1
// CHECK: [[V49:%.+]] = comb.xor [[V19]], %true{{.*}} : i1
// CHECK: [[V50:%.+]] = comb.and [[V44]], [[V49]] : i1
// CHECK: [[V51:%.+]] = comb.or %false{{.*}}, [[V50]] : i1
// CHECK: llhd.drv %o, [[V28]] after [[V1]] if [[V51]] : !hw.inout<i5>
// CHECK: llhd.drv %o, [[V27]] after [[V1]] if [[V51]] : !hw.inout<i5>
// CHECK: cf.br ^[[BB1]]
}

Expand Down Expand Up @@ -165,6 +165,68 @@ hw.module @basic(in %cond: i1) {
}
}

hw.module @value_motion(in %a_in : i1, in %clk_in : i1, out b : i1) {
%true = hw.constant true
%false = hw.constant false

// CHECK: [[V0:%.+]] = llhd.constant_time <0ns, 0d, 1e>
// CHECK: [[V1:%.+]] = llhd.constant_time <0ns, 1d, 0e>
%0 = llhd.constant_time <0ns, 0d, 1e>
%1 = llhd.constant_time <0ns, 1d, 0e>

// CHECK: %a = llhd.sig
// CHECK: %clk = llhd.sig
// CHECK: %b = llhd.sig
%a = llhd.sig name "a" %false : i1
%clk = llhd.sig name "clk" %false : i1
%b = llhd.sig %false : i1

// CHECK: [[V2:%.+]] = llhd.prb %clk
%2 = llhd.prb %clk : !hw.inout<i1>

// CHECK: llhd.process
llhd.process {
// CHECK: cf.br ^[[BB1:.+]]
cf.br ^bb1
// CHECK: ^[[BB1]]:
^bb1:
// CHECK: [[V3:%.+]] = llhd.prb %clk
// CHECK: llhd.wait ([[V2]] : i1), ^[[BB2:.+]]
%4 = llhd.prb %clk : !hw.inout<i1>
llhd.wait (%2 : i1), ^bb2
// CHECK: ^[[BB2]]:
^bb2:
// CHECK: [[V4:%.+]] = llhd.prb %clk
// CHECK: [[V5:%.+]] = comb.xor bin [[V3]], %true{{.*}}
// CHECK: [[V6:%.+]] = comb.and bin [[V5]], [[V4]]
%5 = llhd.prb %clk : !hw.inout<i1>
%6 = comb.xor bin %4, %true : i1
%7 = comb.and bin %6, %5 : i1
cf.cond_br %7, ^bb3, ^bb1
^bb3:
%8 = llhd.prb %a : !hw.inout<i1>
%9 = comb.xor %8, %true : i1
llhd.drv %b, %9 after %1 : !hw.inout<i1>
cf.br ^bb1
// CHECK: [[V7:%.+]] = comb.and %true{{.*}}, [[V6]]
// CHECK: [[V8:%.+]] = comb.or %false{{.*}}, [[V7]]
// CHECK: [[V9:%.+]] = llhd.prb %a
// CHECK: [[V10:%.+]] = comb.xor [[V9]], %true{{.*}}
// CHECK: llhd.drv %b, [[V10]] after [[V1]] if [[V8]] : !hw.inout<i1>
// CHECK-NEXT: cf.br ^[[BB1:.+]]
}

// Unused in pass, just check that it stay unmodified
// CHECK: llhd.drv %a, %a_in after [[V0]]
// CHECK: llhd.drv %clk, %clk_in after [[V0]]
// CHECK: [[V11:%.+]] = llhd.prb %b
// CHECK: hw.output [[V11]]
llhd.drv %a, %a_in after %0 : !hw.inout<i1>
llhd.drv %clk, %clk_in after %0 : !hw.inout<i1>
%3 = llhd.prb %b : !hw.inout<i1>
hw.output %3 : i1
}

// The following processes should stay unmodified, just make sure the pass doesn't crash on them

// CHECK-LABEL: hw.module @more_than_one_wait
Expand Down
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