sdalvi-quic opened a new issue, #16577:
URL: https://github.com/apache/tvm/issues/16577
I was trying to understand the use of **T.assume** in the simplification of
expressions and I came across this example in the
"**test_tir_transform_simplify.py**" file named as
"**TestSimplifyUsingPartiallyKnownBufferExpression**". Here, I tried to modify
the test and saw that, it was failing while using the
"**propagate_knowns_to_simplify_expressions**" flag and T.assume statements. I
have attached the test below.
```c++
class TestSimplifyUsingPartiallyKnownBufferExpression(BaseBeforeAfter):
"""An assumption about buffer contents may apply to only part of a buffer
Like TestSimplifyUsingPartiallyKnownBufferConditional, but the
conditional is expressed as part of T.assume, instead of in the
control flow.
"""
# propagate_knowns_to_prove_conditional = True
propagate_knowns_to_simplify_expressions = True
def before(A: T.Buffer(16, "int32")):
for i in T.serial(16):
T.evaluate(T.assume(i < 14 or A[i] == 0))
for i in T.serial(16):
if i < 14:
if A[i] == 0:
A[i] = 42
def expected(A: T.Buffer(16, "int32")):
for i in T.serial(16):
T.evaluate(T.assume(i < 14 or A[i] == 0))
for i in T.serial(16):
if i < 14:
if A[i] == 0:
A[i] = 42
```
Here given the assumption statements `T.assume(i < 14 or A[i] == 0)`, A[i]
will have to be 0 if the range of `i >= 14` but A[i] may or may not be 0 if `i
< 14`. So, we should see the expected code as **above** where no statement is
eliminated. But the IR returned after the pass eliminates the condition `if
A[i] == 0` and returns the IR as **below** :
```c++
def after(A: T.Buffer((16,), "int32")):
T.func_attr({"global_symbol": "main"})
for i in range(16):
T.assume(i < 14 or A[i] == 0)
for i in range(16):
if i < 14:
A[i] = 42
```
I see that the two flags "**propagate_knowns_to_simplify_expressions**" and
"**propagate_knowns_to_prove_conditional** " are internally calling the
function **SimplifyInContext** which is simplifying using the line :
```c++
expr = control_flow_block.known_at_block_start.SubstituteKnownBufferValues(
std::move(expr), axis_var_lookup_, analyzer);
```
Can you please help to fix the issue with the test or point what
modification needs to be done?
According to my understanding there is either an issue with the control flow
graph generated when T.assume statement are present or there needs to be slight
changes in the **SimplifyInContext** function which is simplifying the
expression, please correct me if I am wrong.
@Lunderberg, it will be helpful if you could help with this issue.
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