Create an initial testing TODO list.

ml-proto/TestingTodo.md

@@ -0,0 +1,101 @@
+This is a rough list of "tests to write". Everything here should either be
+specified in
+[AstSemantics.md](https://github.com/WebAssembly/design/blob/master/AstSemantics.md),
+have a link to an open issue/PR, or be obvious. Comments/corrections/additions
+welcome.
+
+Misc semantics:
+ - test that linear memory is little-endian for all integers and floats
+ - test that unaligned and misaligned accesses work, even if slow
+ - test that runaway recursion traps
+ - test that too-big linear memory resize fails appropriately
+ - test that too-big linear memory initial allocation fails
+ - test that function addresses are monotonic indices, and not actual addresses.
+ - test that one can clobber the entire contents of the linear memory without corrupting: call stack, global variables, local variables, program execution.
+
+Operator semantics:
+ - test that promote/demote, sext/trunc, zext/trunc is bit-preserving if not NaN
+ - test that clz/ctz handle zero
+ - test that numbers slightly outside of the int32 range round into the int32 range in floating-to-int32 conversion
+ - test that neg, abs, copysign, reinterpretcast, store+load, set+get, preserve the sign bit and significand bits of NaN and don't canonicalize
+ - test that shifts don't mask their shift count. 32 is particularly nice to test.
+ - test that `page_size` returns something sane [(power of 2?)](https://github.com/WebAssembly/design/pull/296)
+ - test that arithmetic operands are evaluated left-to-right
+ - test that add/sub/mul/wrap/wrapping-store silently wrap on overflow
+ - test that sdiv/udiv/srem/urem trap on divide-by-zero
+ - test that sdiv traps on overflow
+ - test that srem doesn't trap when the corresponding sdiv would overflow
+ - test that float-to-integer conversion traps on overflow and invalid
+ - test that unsigned operations are properly unsigned
+
+Floating point semantics:
+ - test for round-to-nearest rounding
+ - test for ties-to-even rounding
+ - test that all operations with floating point inputs correctly handle all their NaN, -0, 0, Infinity, and -Infinity special cases
+ - test that all operations that can overflow produce Infinity and with the correct sign
+ - test that all operations that can divide by zero produce Infinity with the correct sign
+ - test that all operations that can have an invalid produce NaN
+ - test that all operations that can have underflow behave [correctly](https://github.com/WebAssembly/design/issues/148)
+ - test that nearestint doesn't do JS-style Math.round or C-style round(3) rounding
+ - test that signalling NaN doesn't cause weirdness
+ - test that signalling/quiet NaNs can have sign bits and payloads in literals
+ - test that conversion from int32/int64 to float32 rounds correctly
+
+Linear memory semantics:
+ - test that loading from null works
+ - test that loading from constant OOB traps and is not DCE'd or folded (pending [discussion](https://github.com/WebAssembly/design/blob/master/AstSemantics.md#out-of-bounds))
+ - test that loading from "beyond the STACKPTR" succeeds
+ - test that "stackptr + (linearmemptr - stackptr)" loads from linearmemptr.
+ - test loading "uninitialized" things from aliased stack frames return what's there
+ - test that loadwithoffset traps in overflow cases
+ - test that newly allocated memory is zeroed
+
+Function pointer semantics:
+ - test that function pointers work [correctly](https://github.com/WebAssembly/design/issues/89)
+
+Expression optimizer bait:
+ - test that `a+1<b+1` isn't folded to `a<b`
+ - test that that demote-promote, wrap+sext, wrap+zext, shl+ashr, shl+lshr, div+mul, mul+div aren't folded away
+ - test that converting int32 to float and back isn't folded away
+ - test that converting int64 to double and back isn't folded away
+ - test that `float(double(float(x))+double(y))` is not `float(x)+float(y)` (and so on for other operators)
+ - test that `x*0.0` is not folded to `0.0`
+ - test that `0.0/x` is not folded to `0.0`
+ - test that signed integer div by negative constant is not ashr
+ - test that signed integer div rounds toward zero
+ - test that signed integer mod has the sign of the dividend
+ - test unsigned and signed division by 3, 5, 7
+ - test that floating-point division by immediate 0 and -0 is defined
+ - test that ueq/one/etc aren't folded to oeq/une/etc.
+ - test that floating point add/mul aren't reassociated even when tempting
+ - test that floating point mul+add isn't folded to fma even when tempting
+ - test that 1/x isn't translated into reciprocal-approximate
+ - test that 1/sqrt(x) isn't approximated either
+ - test that fp division by non-power-2 constant gets full precision (isn't a multiply-by-reciprocal deal)?
+
+Misc optimizer bait:
+ - test that the impl doesn't constant-fold away or DCE away or speculate operations that should trap, such as `1/0u`, `1/0`, `1%0u`, `1%0, convertToInt(NaN)`, `INT_MIN/-1` and so on.
+ - test that likely constant folding uses the correct rounding mode
+ - test that the scheduler doesn't move a trapping div past a call which may not return
+ - test that redundant-load elimination, dead-store elimination, and/or store+load forwarding correctly respect interfering stores of different types (aka no TBAA)
+ - test that linearized multidimensional array accesses can have overindexing in interesting ways
+ - test that 32-bit loop induction variables that wrap aren't promoted to 64-bit
+
+Misc x86 optimizer bait:
+ - test that oeq handles NaN right in if, if-else, and setcc cases
+
+Misc x87-isms:
+ - test for invalid Precision-Control-style x87 math
+ - test for invalid -ffloat-store-style x87 math
+ - test for evaluating intermediate results at greater precision
+ - test for loading and storing NaNs
+
+Control flow:
+ - test that continue goes to the right place in `do_while` and `forever`
+ - test that break goes to the right place in all cases where it can appear
+ - test devious switch case patterns
+
+Validation errors:
+ - load/store or variables with type void/bool/funcptr/etc.
+ - sign-extend load from int64 to int32 etc.
+ - fp-promote load and fp-demote store