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fpu coverage improvements

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This commit is contained in:
David Harris 2024-01-21 13:17:56 -08:00
parent 9d4a14b209
commit ff055c404c
3 changed files with 26 additions and 4 deletions
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2
src/fpu/postproc/cvtshiftcalc.sv
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@ -98,6 +98,6 @@ module cvtshiftcalc import cvw::*; #(parameter cvw_t P) (
// determine if the result underflows ??? -> fp
// - if the first 1 is shifted out of the result then the result underflows
// - can't underflow an integer to fp conversions
assign CvtResUf = ($signed(CvtCe) < $signed({{P.NE-$clog2(P.NF){1'b1}}, ResNegNF}))&~XZero&~IntToFp;
assign CvtResUf = ($signed(CvtCe) < $signed({{P.NE-$clog2(P.NF){1'b1}}, ResNegNF}))&~XZero; // dh &~IntToFp not necessary because integer to float conversion never underflows
endmodule

6
src/fpu/postproc/fmashiftcalc.sv
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@ -101,9 +101,9 @@ module fmashiftcalc import cvw::*; #(parameter cvw_t P) (
assign Sum2GEFL = $signed(PreNormSumExp) >= $signed((P.NE+2)'(-P.NF2-2+P.BIAS-P.BIAS2)) | ~|PreNormSumExp;
always_comb begin
case (Fmt)
P.FMT: FmaPreResultSubnorm = Sum0LEZ & Sum0GEFL & ~FmaSZero;
P.FMT1: FmaPreResultSubnorm = Sum1LEZ & Sum1GEFL & ~FmaSZero;
P.FMT2: FmaPreResultSubnorm = Sum2LEZ & Sum2GEFL & ~FmaSZero;
P.FMT: FmaPreResultSubnorm = Sum0LEZ & Sum0GEFL; // & ~FmaSZero; // checking sum is not zero is harmless but turns out to be unnecessary
P.FMT1: FmaPreResultSubnorm = Sum1LEZ & Sum1GEFL; // & ~FmaSZero;
P.FMT2: FmaPreResultSubnorm = Sum2LEZ & Sum2GEFL; // & ~FmaSZero;
default: FmaPreResultSubnorm = 1'bx;
endcase
end

22
tests/coverage/fpu.S
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@ -164,6 +164,28 @@ main:
fcvt.s.w ft2, zero
fdiv.s ft3, ft1, ft2
/* These didn't make a difference
// Test subtraction of identical denormalized numbers with to exercise FmaPreResultSubnorm logic with FmaSZero
li t0, 0xFFFFFFFF00000001
fmv.w.x ft1, t0 // smallest denorm
fsub.s ft1, ft1, ft1 // difference = 0
li t0, 0x0000000000000001
fmv.d.x ft1, t0 // smallest denorm
fsub.d ft1, ft1, ft1 // difference = 0
// Test subtraction of identical denormalized numbers with to exercise FmaPreResultSubnorm logic with FmaSZero
li t0, 0xFFFFFFFF00100001
fmv.w.x ft1, t0 // almost largest denorm
fsub.s ft1, ft1, ft1 // difference = 0
li t0, 0x0001000000000001
fmv.d.x ft1, t0 // smallest denorm
fsub.d ft1, ft1, ft1 // difference = 0
*/
# Test floating point convert to integer and using result
fcvt.w.s t0, f0
add t1, t0, t0