[InstCombine] Transform high latency, dependent FSQRT/FDIV into FMUL (#87474)
The proposed patch, in general, tries to transform the below code
sequence:
x = 1.0 / sqrt (a);
r1 = x * x; // same as 1.0 / a
r2 = a / sqrt(a); // same as sqrt (a)
TO
(If x, r1 and r2 are all used further in the code)
r1 = 1.0 / a
r2 = sqrt (a)
x = r1 * r2
The transform tries to make high latency sqrt and div operations
independent and also saves on one multiplication.
The patch was tested with SPEC17 suite with cpu=neoverse-v2. The
performance uplift achieved was:
544.nab_r ~4%
No other regressions were observed. Also, no compile time differences
were observed with the patch.
Closes #54652
llvm-project
7253c6fd - [InstCombine] Transform high latency, dependent FSQRT/FDIV into FMUL (#87474)
