tree 656535e272a408dda7400fda5d570b1491f708f3
parent 82d91083cb56c89d2cb8e9d56d4d69f07ac34fed
author Nicolas Capens <capn@google.com> 1654013036 -0400
committer GitHub <noreply@github.com> 1654013036 -0400
gpgsig -----BEGIN PGP SIGNATURE-----
 
 wsBcBAABCAAQBQJiljxsCRBK7hj4Ov3rIwAA/O0IADeQm4bhG1P9ZGnoWWmzjyr6
 1scEn50AlJSHWdwniszdYuQlUu0JKuw1WroC6gMeGH5IEJi40zI/jMmNM6vzizEU
 drD/0YylcURhzKWNXR/U97/XCl67o/OiwIQ3AJoChawkIk1PH2WMxJ8ibasG/1ve
 WjNP6FXEtzxnRsq4k0Pi9b3RQQJxfn/i0Ld1jubQ1xxaSTecGo3wSJAesgMFihpB
 k04rZ2Iex3nXkkChVm2nHiGMOnXOXjY+36GxlYyZ+vFCLYPZC3dfoPrxSNeuZEOg
 WRYtRyHJZAanw/TQg3r6Q5Z47/mD9SlmA/+B5swzDLssO32e4C4at0VNMeoq/Dg=
 =hLc2
 -----END PGP SIGNATURE-----
 

Fold multiply and subtraction into FMA with negation (#4808)

This change adds a folding rule which transforms x * y - a and a - x * y
into FMA(x, y, -a) and FMA(-x, y, a), respectively.

While the SPIR-V instruction count remains the same, target instruction
sets typically feature FMA instruction variants that can negate an
operand. Also this transformation may unlock further optimizations which
eliminate the negation.

(Google bug: b/226145988)