https://bugs.llvm.org/show_bug.cgi?id=49738
Bug ID: 49738
Summary: [Matrix] LowerMatrixIntrinsics should preserve
existing fast-math flags during lowering
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: Scalar Optimizations
Assignee: unassignedb...@nondot.org
Reporter: florian_h...@apple.com
CC: llvm-bugs@lists.llvm.org
Currently LowerMatrixIntrinsics does not add existing fast-math flags from
matrix intrinsics & other instructions with shape information to the lowered
instructions.
For the example below, `opt -lower-matrix-intrinsics` creates fmuladd/fadd/fmul
instructions without `fast`: https://godbolt.org/z/1o48Tx1bP
This also means we fail to fold redundant FP instructions. In this case, we end
up with fmuladd calls with operands that are zero and can be simplified with
`fast`: https://godbolt.org/z/5oWs1oh91
define <4 x float> @foo(<4 x float> %m, float %x, float %y) {
%i1 = insertelement <4 x float> <float poison, float 0.000000e+00, float
0.000000e+00, float poison>, float %x, i64 0
%i2 = insertelement <4 x float> %i1, float %y, i64 3
%res = tail call fast <4 x float> @llvm.matrix.multiply.v4f32.v4f32.v4f32(<4
x float> %m, <4 x float> %i1, i32 2, i32 2, i32 2)
%res.2 = fadd fast <4 x float> %res, %m
ret <4 x float> %res
}
declare <4 x float> @llvm.matrix.multiply.v4f32.v4f32.v4f32(<4 x float>, <4 x
float>, i32, i32, i32)
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