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[DAG] SimplifyDemandedBits - don't early-out for multiple use values
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SimplifyDemandedBits currently early-outs for multi-use values beyond the root node (just returning the knownbits), which is missing a number of optimizations as there are plenty of cases where we can still simplify when initially demanding all elements/bits.

@lenary has confirmed that the test cases in aea-erratum-fix.ll need refactoring and the current increase codegen is not a major concern.

Differential Revision: https://reviews.llvm.org/D129765
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@RKSimon
RKSimon committed Jul 27, 2022
1 parent ea460b7 commit 529bd4f
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Showing 26 changed files with 1,843 additions and 1,708 deletions.
23 changes: 15 additions & 8 deletions llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1089,6 +1089,10 @@ bool TargetLowering::SimplifyDemandedBits(
if (Op.isUndef())
return false;

// We can't simplify target constants.
if (Op.getOpcode() == ISD::TargetConstant)
return false;

if (Op.getOpcode() == ISD::Constant) {
// We know all of the bits for a constant!
Known = KnownBits::makeConstant(cast<ConstantSDNode>(Op)->getAPIntValue());
Expand All @@ -1103,17 +1107,16 @@ bool TargetLowering::SimplifyDemandedBits(
}

// Other users may use these bits.
bool HasMultiUse = false;
if (!Op.getNode()->hasOneUse() && !AssumeSingleUse) {
if (Depth != 0) {
// If not at the root, Just compute the Known bits to
// simplify things downstream.
Known = TLO.DAG.computeKnownBits(Op, DemandedElts, Depth);
if (Depth >= SelectionDAG::MaxRecursionDepth) {
// Limit search depth.
return false;
}
// If this is the root being simplified, allow it to have multiple uses,
// just set the DemandedBits/Elts to all bits.
// Allow multiple uses, just set the DemandedBits/Elts to all bits.
DemandedBits = APInt::getAllOnes(BitWidth);
DemandedElts = APInt::getAllOnes(NumElts);
HasMultiUse = true;
} else if (OriginalDemandedBits == 0 || OriginalDemandedElts == 0) {
// Not demanding any bits/elts from Op.
return TLO.CombineTo(Op, TLO.DAG.getUNDEF(VT));
Expand All @@ -1124,8 +1127,6 @@ bool TargetLowering::SimplifyDemandedBits(

KnownBits Known2;
switch (Op.getOpcode()) {
case ISD::TargetConstant:
llvm_unreachable("Can't simplify this node");
case ISD::SCALAR_TO_VECTOR: {
if (!DemandedElts[0])
return TLO.CombineTo(Op, TLO.DAG.getUNDEF(VT));
Expand Down Expand Up @@ -2715,6 +2716,12 @@ bool TargetLowering::SimplifyDemandedBits(
APFloat(TLO.DAG.EVTToAPFloatSemantics(VT), Known.One), dl, VT));
}

// A multi use 'all demanded elts' simplify failed to find any knownbits.
// Try again just for the original demanded elts.
// Ensure we do this AFTER constant folding above.
if (HasMultiUse && Known.isUnknown() && !OriginalDemandedElts.isAllOnes())
Known = TLO.DAG.computeKnownBits(Op, OriginalDemandedElts, Depth);

return false;
}

Expand Down
130 changes: 59 additions & 71 deletions llvm/test/CodeGen/AArch64/fptosi-sat-vector.ll
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2616,36 +2616,36 @@ define <8 x i100> @test_signed_v8f16_v8i100(<8 x half> %f) {
; CHECK-NEXT: mov w8, #1895825407
; CHECK-NEXT: ldr q0, [sp, #32] // 16-byte Folded Reload
; CHECK-NEXT: mov x25, #-34359738368
; CHECK-NEXT: mov x23, #34359738367
; CHECK-NEXT: mov x22, #34359738367
; CHECK-NEXT: fmov s9, w8
; CHECK-NEXT: fcmp s8, s10
; CHECK-NEXT: mov h0, v0.h[3]
; CHECK-NEXT: csel x8, xzr, x0, lt
; CHECK-NEXT: csel x9, x25, x1, lt
; CHECK-NEXT: csel x8, x25, x1, lt
; CHECK-NEXT: csel x9, xzr, x0, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: csel x9, x23, x9, gt
; CHECK-NEXT: csinv x8, x8, xzr, le
; CHECK-NEXT: csinv x9, x9, xzr, le
; CHECK-NEXT: csel x8, x22, x8, gt
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fcvt s8, h0
; CHECK-NEXT: csel x8, xzr, x8, vs
; CHECK-NEXT: fmov s0, s8
; CHECK-NEXT: str x8, [sp, #24] // 8-byte Folded Spill
; CHECK-NEXT: csel x8, xzr, x9, vs
; CHECK-NEXT: str x8, [sp, #72] // 8-byte Folded Spill
; CHECK-NEXT: csel x8, xzr, x9, vs
; CHECK-NEXT: str x8, [sp, #24] // 8-byte Folded Spill
; CHECK-NEXT: bl __fixsfti
; CHECK-NEXT: fcmp s8, s10
; CHECK-NEXT: ldr q0, [sp, #32] // 16-byte Folded Reload
; CHECK-NEXT: csel x8, xzr, x0, lt
; CHECK-NEXT: csel x9, x25, x1, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: csel x9, x23, x9, gt
; CHECK-NEXT: csel x9, x22, x9, gt
; CHECK-NEXT: csinv x8, x8, xzr, le
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fcvt s8, h0
; CHECK-NEXT: csel x8, xzr, x8, vs
; CHECK-NEXT: csel x22, xzr, x9, vs
; CHECK-NEXT: csel x10, xzr, x8, vs
; CHECK-NEXT: csel x8, xzr, x9, vs
; CHECK-NEXT: fmov s0, s8
; CHECK-NEXT: str x8, [sp, #16] // 8-byte Folded Spill
; CHECK-NEXT: stp x8, x10, [sp, #8] // 16-byte Folded Spill
; CHECK-NEXT: bl __fixsfti
; CHECK-NEXT: ldr q0, [sp, #32] // 16-byte Folded Reload
; CHECK-NEXT: fcmp s8, s10
Expand All @@ -2654,10 +2654,10 @@ define <8 x i100> @test_signed_v8f16_v8i100(<8 x half> %f) {
; CHECK-NEXT: csel x9, xzr, x0, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: csinv x9, x9, xzr, le
; CHECK-NEXT: csel x8, x23, x8, gt
; CHECK-NEXT: csel x8, x22, x8, gt
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fcvt s8, h0
; CHECK-NEXT: csel x24, xzr, x8, vs
; CHECK-NEXT: csel x26, xzr, x8, vs
; CHECK-NEXT: csel x8, xzr, x9, vs
; CHECK-NEXT: fmov s0, s8
; CHECK-NEXT: str x8, [sp, #32] // 8-byte Folded Spill
Expand All @@ -2669,40 +2669,39 @@ define <8 x i100> @test_signed_v8f16_v8i100(<8 x half> %f) {
; CHECK-NEXT: csel x9, xzr, x0, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: csinv x9, x9, xzr, le
; CHECK-NEXT: csel x8, x23, x8, gt
; CHECK-NEXT: csel x8, x22, x8, gt
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fcvt s8, h0
; CHECK-NEXT: csel x27, xzr, x8, vs
; CHECK-NEXT: csel x28, xzr, x8, vs
; CHECK-NEXT: csel x8, xzr, x9, vs
; CHECK-NEXT: fmov s0, s8
; CHECK-NEXT: str x8, [sp, #8] // 8-byte Folded Spill
; CHECK-NEXT: str x8, [sp] // 8-byte Folded Spill
; CHECK-NEXT: bl __fixsfti
; CHECK-NEXT: ldr q0, [sp, #48] // 16-byte Folded Reload
; CHECK-NEXT: fcmp s8, s10
; CHECK-NEXT: mov h0, v0.h[3]
; CHECK-NEXT: csel x8, xzr, x0, lt
; CHECK-NEXT: csel x9, x25, x1, lt
; CHECK-NEXT: csel x8, x25, x1, lt
; CHECK-NEXT: csel x9, xzr, x0, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: csel x9, x23, x9, gt
; CHECK-NEXT: csinv x8, x8, xzr, le
; CHECK-NEXT: csinv x9, x9, xzr, le
; CHECK-NEXT: csel x8, x22, x8, gt
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fcvt s8, h0
; CHECK-NEXT: csel x8, xzr, x8, vs
; CHECK-NEXT: csel x29, xzr, x9, vs
; CHECK-NEXT: csel x27, xzr, x8, vs
; CHECK-NEXT: csel x20, xzr, x9, vs
; CHECK-NEXT: fmov s0, s8
; CHECK-NEXT: str x8, [sp] // 8-byte Folded Spill
; CHECK-NEXT: bl __fixsfti
; CHECK-NEXT: fcmp s8, s10
; CHECK-NEXT: ldr q0, [sp, #48] // 16-byte Folded Reload
; CHECK-NEXT: csel x8, xzr, x0, lt
; CHECK-NEXT: csel x9, x25, x1, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: csel x9, x23, x9, gt
; CHECK-NEXT: csel x9, x22, x9, gt
; CHECK-NEXT: csinv x8, x8, xzr, le
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fcvt s8, h0
; CHECK-NEXT: csel x20, xzr, x8, vs
; CHECK-NEXT: csel x28, xzr, x9, vs
; CHECK-NEXT: csel x29, xzr, x8, vs
; CHECK-NEXT: csel x21, xzr, x9, vs
; CHECK-NEXT: fmov s0, s8
; CHECK-NEXT: bl __fixsfti
; CHECK-NEXT: ldr q0, [sp, #48] // 16-byte Folded Reload
Expand All @@ -2712,65 +2711,54 @@ define <8 x i100> @test_signed_v8f16_v8i100(<8 x half> %f) {
; CHECK-NEXT: csel x9, xzr, x0, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: csinv x9, x9, xzr, le
; CHECK-NEXT: csel x8, x23, x8, gt
; CHECK-NEXT: csel x8, x22, x8, gt
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fcvt s8, h0
; CHECK-NEXT: csel x21, xzr, x8, vs
; CHECK-NEXT: csel x26, xzr, x9, vs
; CHECK-NEXT: csel x23, xzr, x8, vs
; CHECK-NEXT: csel x24, xzr, x9, vs
; CHECK-NEXT: fmov s0, s8
; CHECK-NEXT: bl __fixsfti
; CHECK-NEXT: fmov d0, x20
; CHECK-NEXT: fcmp s8, s10
; CHECK-NEXT: ldr x11, [sp, #8] // 8-byte Folded Reload
; CHECK-NEXT: lsr x10, x28, #28
; CHECK-NEXT: ldr d1, [sp] // 8-byte Folded Reload
; CHECK-NEXT: lsr x12, x29, #28
; CHECK-NEXT: mov v0.d[1], x28
; CHECK-NEXT: extr x9, x21, x29, #28
; CHECK-NEXT: bfi x23, x20, #36, #28
; CHECK-NEXT: extr x11, x27, x20, #28
; CHECK-NEXT: str x24, [x19]
; CHECK-NEXT: csel x8, x25, x1, lt
; CHECK-NEXT: csel x9, xzr, x0, lt
; CHECK-NEXT: csel x10, xzr, x0, lt
; CHECK-NEXT: fcmp s8, s9
; CHECK-NEXT: stur x11, [x19, #75]
; CHECK-NEXT: ldr x13, [sp, #32] // 8-byte Folded Reload
; CHECK-NEXT: csinv x9, x9, xzr, le
; CHECK-NEXT: csel x8, x23, x8, gt
; CHECK-NEXT: stur x9, [x19, #41]
; CHECK-NEXT: stp x23, x11, [x19, #8]
; CHECK-NEXT: lsr x11, x27, #28
; CHECK-NEXT: csinv x9, x10, xzr, le
; CHECK-NEXT: lsr x10, x21, #28
; CHECK-NEXT: csel x8, x22, x8, gt
; CHECK-NEXT: fcmp s8, s8
; CHECK-NEXT: fmov x11, d0
; CHECK-NEXT: stur x13, [x19, #50]
; CHECK-NEXT: mov v1.d[1], x29
; CHECK-NEXT: ldr d0, [sp, #16] // 8-byte Folded Reload
; CHECK-NEXT: csel x9, xzr, x9, vs
; CHECK-NEXT: strb w10, [x19, #49]
; CHECK-NEXT: extr x10, x28, x11, #28
; CHECK-NEXT: csel x8, xzr, x8, vs
; CHECK-NEXT: bfi x8, x11, #36, #28
; CHECK-NEXT: strb w12, [x19, #24]
; CHECK-NEXT: ldr x10, [sp] // 8-byte Folded Reload
; CHECK-NEXT: csel x9, xzr, x9, vs
; CHECK-NEXT: bfi x8, x29, #36, #28
; CHECK-NEXT: strb w11, [x19, #24]
; CHECK-NEXT: stur x10, [x19, #75]
; CHECK-NEXT: ldp x12, x11, [sp, #8] // 16-byte Folded Reload
; CHECK-NEXT: stur x9, [x19, #25]
; CHECK-NEXT: fmov x12, d1
; CHECK-NEXT: stur x10, [x19, #41]
; CHECK-NEXT: lsr x9, x22, #28
; CHECK-NEXT: ldr d1, [sp, #24] // 8-byte Folded Reload
; CHECK-NEXT: stur x8, [x19, #33]
; CHECK-NEXT: ldr x8, [sp, #32] // 8-byte Folded Reload
; CHECK-NEXT: extr x10, x12, x11, #28
; CHECK-NEXT: bfi x28, x11, #36, #28
; CHECK-NEXT: stur x8, [x19, #50]
; CHECK-NEXT: ldr x9, [sp, #24] // 8-byte Folded Reload
; CHECK-NEXT: ldr x11, [sp, #72] // 8-byte Folded Reload
; CHECK-NEXT: extr x18, x29, x12, #28
; CHECK-NEXT: mov v0.d[1], x22
; CHECK-NEXT: bfi x21, x12, #36, #28
; CHECK-NEXT: str x26, [x19]
; CHECK-NEXT: mov v1.d[1], x11
; CHECK-NEXT: lsr x10, x11, #28
; CHECK-NEXT: mov x13, x11
; CHECK-NEXT: stp x21, x18, [x19, #8]
; CHECK-NEXT: fmov x8, d0
; CHECK-NEXT: strb w9, [x19, #99]
; CHECK-NEXT: strb w10, [x19, #74]
; CHECK-NEXT: fmov x11, d1
; CHECK-NEXT: extr x12, x22, x8, #28
; CHECK-NEXT: bfi x27, x8, #36, #28
; CHECK-NEXT: extr x8, x13, x11, #28
; CHECK-NEXT: bfi x24, x11, #36, #28
; CHECK-NEXT: stur x12, [x19, #91]
; CHECK-NEXT: stur x27, [x19, #83]
; CHECK-NEXT: stur x10, [x19, #91]
; CHECK-NEXT: stur x28, [x19, #83]
; CHECK-NEXT: extr x8, x11, x9, #28
; CHECK-NEXT: bfi x26, x9, #36, #28
; CHECK-NEXT: lsr x9, x12, #28
; CHECK-NEXT: stur x8, [x19, #66]
; CHECK-NEXT: stur x24, [x19, #58]
; CHECK-NEXT: lsr x8, x11, #28
; CHECK-NEXT: stur x26, [x19, #58]
; CHECK-NEXT: strb w9, [x19, #99]
; CHECK-NEXT: strb w8, [x19, #74]
; CHECK-NEXT: ldp x20, x19, [sp, #176] // 16-byte Folded Reload
; CHECK-NEXT: ldp x22, x21, [sp, #160] // 16-byte Folded Reload
; CHECK-NEXT: ldp x24, x23, [sp, #144] // 16-byte Folded Reload
Expand Down
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