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Fix local confusion in builtin min/max/rotl/rotr #1540

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Merged
merged 4 commits into from
Nov 9, 2020
Merged

Fix local confusion in builtin min/max/rotl/rotr #1540

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1aa8b1d
Fix local confusion in builtin min/max
dcodeIO Nov 9, 2020
3683ffd
update affected tests
dcodeIO Nov 9, 2020
0b40161
harden rotl, fix rotr
dcodeIO Nov 9, 2020
3c5a09d
Merge branch 'master' into issue-1537
dcodeIO Nov 9, 2020
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30 changes: 29 additions & 1 deletion package-lock.json
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9 changes: 5 additions & 4 deletions src/builtins.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,7 @@ import {
} from "./program";

import {
findUsedLocals,
FlowFlags,
LocalFlags
} from "./flow";
Expand Down Expand Up @@ -1185,7 +1186,7 @@ function builtin_rotl(ctx: BuiltinContext): ExpressionRef {
case TypeKind.U16: {
// (value << (shift & mask)) | (value >>> ((0 - shift) & mask))
let flow = compiler.currentFlow;
let temp1 = flow.getTempLocal(type);
let temp1 = flow.getTempLocal(type, findUsedLocals(arg1));
flow.setLocalFlag(temp1.index, LocalFlags.WRAPPED);
let temp2 = flow.getTempLocal(type);
flow.setLocalFlag(temp2.index, LocalFlags.WRAPPED);
Expand Down Expand Up @@ -1266,7 +1267,7 @@ function builtin_rotr(ctx: BuiltinContext): ExpressionRef {
case TypeKind.U16: {
// (value >>> (shift & mask)) | (value << ((0 - shift) & mask))
let flow = compiler.currentFlow;
let temp1 = flow.getTempLocal(type);
let temp1 = flow.getTempLocal(type, findUsedLocals(arg1));
flow.setLocalFlag(temp1.index, LocalFlags.WRAPPED);
let temp2 = flow.getTempLocal(type);
flow.setLocalFlag(temp2.index, LocalFlags.WRAPPED);
Expand Down Expand Up @@ -1484,7 +1485,7 @@ function builtin_max(ctx: BuiltinContext): ExpressionRef {
if (op != -1) {
let flow = compiler.currentFlow;
let nativeType = type.toNativeType();
let temp1 = flow.getTempLocal(type);
let temp1 = flow.getTempLocal(type, findUsedLocals(arg1));
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@MaxGraey MaxGraey Nov 9, 2020 •
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how about make getUnusedLocal which try to find unused local in already allocated locals or allocate new one otherwise? And use flow.getUnusedLocal(type) here and in other places?

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findUsedLocals is what other code typically uses to keep the number of necessary locals low. Otherwise we'd always get a new local, never a reused one, I guess?

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Also builtin_abs, builtin_rotl / builtin_rotr I guess also required this fix

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Btw, at some point I expect us to move away from free'ing temporary locals, but we'll have to get rid of any kind of recompiling expressions first. There are still a few places doing this, and getUnusedLocal would return a new local upon recompile, yielding different code, while findUsedLocals doesn't.

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Also builtin_abs, builtin_rotl / builtin_rotr I guess also required this fix

Abs is a unary expression not executing input code in between assignment and usage of the temporary locals. Should be safe. Going to take a look at rotl/rotr.

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findUsedLocals is what other code typically uses to keep the number of necessary locals low. Otherwise we'd always get a new local, never a reused one, I guess?

I guess better always alloc new loacal and let binaryen optimize all of this afterwards

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@dcodeIO dcodeIO Nov 9, 2020 •
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I expect us to move into that direction, yeah, but we cannot do that as long as we are recompiling code (and not resetting the local pool with a new mechanism) because it would confuse local flags (adding new locals on each recompile, leaving earlier ones unused), then for example leading to infinite loops when attempting to unify local flags in loops.

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Seems that rotl for some reason does not exhibit the behavior on rotl(a, rotl(b, c)), but should be susceptible just as rotr is, which trivially breaks without the fix. Probably coincidence. Applied the same fix for both.

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@MaxGraey MaxGraey Nov 9, 2020 •
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then for example leading to infinite loops when attempting to unify local flags in loops.

I see. Ok, in this case PR LGTM

flow.setLocalFlag(temp1.index, LocalFlags.WRAPPED);
let temp2 = flow.getTempLocal(type);
flow.setLocalFlag(temp2.index, LocalFlags.WRAPPED);
Expand Down Expand Up @@ -1563,7 +1564,7 @@ function builtin_min(ctx: BuiltinContext): ExpressionRef {
if (op != -1) {
let flow = compiler.currentFlow;
let nativeType = type.toNativeType();
let temp1 = flow.getTempLocal(type);
let temp1 = flow.getTempLocal(type, findUsedLocals(arg1));
flow.setLocalFlag(temp1.index, LocalFlags.WRAPPED);
let temp2 = flow.getTempLocal(type);
flow.setLocalFlag(temp2.index, LocalFlags.WRAPPED);
Expand Down
22 changes: 22 additions & 0 deletions tests/compiler/builtins.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -561,3 +561,25 @@ assert(isInteger<ReturnType<() => i32>>());
assert(isInteger<returnof<() => i32>>());
assert(isManaged<returnof<() => C>>());
assert(isManaged<ReturnType<() => C>>());

// Issue #1537: Make sure temp. locals are not confused

function max3(a: i32, b: i32, c: i32): i32 {
return max(a, max(b, c));
}
assert(max3(3, 2, 1) == 3);

function min3(a: i32, b: i32, c: i32): i32 {
return min(a, min(b, c));
}
assert(min3(1, 2, 3) == 1);

function rotl3(a: i8, b: i8, c: i8): i32 {
return rotl(a, rotl(b, c));
}
assert(rotl3(3, 2, 1) == 48);

function rotr3(a: i8, b: i8, c: i8): i32 {
return rotr(a, rotr(b, c));
}
assert(rotr3(48, 8, 1) == 3);
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