aaron.ballman added inline comments.
================
Comment at: clang/test/CodeGen/eval-method-fast-math.c:83
+#pragma float_control(pop)
+
+int getFPEvalMethod() {
----------------
zahiraam wrote:
> aaron.ballman wrote:
> > What should happen in a case like this?
> > ```
> > int whatever(float a, float b, float c) {
> > #pragma float_control(precise, off)
> > res = a + b + c;
> > int val = __FLT_EVAL_METHOD__;
> > #pragma float_control(precise, on)
> > return __FLT_EVAL_METHOD__;
> > }
> > ```
> > I would expect that `int val` would hold `-1` and the return statement
> > would return `0`?
> This test case is failing with this error (at the second pragma):
>
> t1.cpp:9:11: error: '#pragma float_control' can only appear at file scope
> or at
> the start of a compound statement
> #pragma float_control(precise, off)
> ^
> 1 error generated.
>
> Tried this:
>
> int whatever(float a, float b, float c) {
> #pragma float_control(precise, off)
> res = a + b + c;
> int val =__FLT_EVAL_METHOD__;
> {
> #pragma float_control(precise, on)
> return __FLT_EVAL_METHOD__;
> }
> }
>
> This generated these last IR instructions:
> store float %add1, float* @"?res@@3MA", align 4
> store i32 -1, i32* %val, align 4
> ret i32 -1
>
> Not sure if this is correct. I guess the first pragma (off) didn't popped, so
> it's still on? But inside the scope of the second pragma the first pragma
> shouldn't be visible? Not sure what should happen here.
> Not sure if this is correct.
It looks incorrect to me. What I'd expect is:
```
int whatever(float a, float b, float c) {
#pragma float_control(precise, off)
res = a + b + c;
int val =__FLT_EVAL_METHOD__; // Expect -1
{
#pragma float_control(precise, on)
return __FLT_EVAL_METHOD__; // Expect 0
}
return __FLT_EVAL_METHOD__; // Expect -1
}
```
I forgot about the function scope restrictions, but the file scope still has an
interesting case worth testing:
```
float a = 1.0f, b = 2.0f, c = 3.0f;
#pragma float_control(precise, off)
float res = a + b + c;
int off =__FLT_EVAL_METHOD__; // Expect -1
#pragma float_control(precise, on)
float other_res = a + b + c;
int on = __FLT_EVAL_METHOD__; // Expect 0
```
Both of these are based on the idea that the float control pragma sets the flag
until it's either popped (by leaving a compound statement) or it's changed to
something else (by another pragma).
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D121122/new/
https://reviews.llvm.org/D121122
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