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gallivm: Use simple scaling plus casting in more unorm->float cases.

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This commit is contained in:
José Fonseca 2011-02-19 10:25:43 +00:00
parent b1002e4aa5
commit 57d4e922a6
1 changed files with 36 additions and 27 deletions
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63
src/gallium/auxiliary/gallivm/lp_bld_conv.c
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@ -231,45 +231,54 @@ lp_build_unsigned_norm_to_float(struct gallivm_state *gallivm,
assert(dst_type.floating);
/* Special-case int8->float, though most cases could be handled
* this way:
*/
if (src_width == 8) {
scale = 1.0/255.0;
mantissa = lp_mantissa(dst_type);
if (src_width <= (mantissa + 1)) {
/*
* The source width matches fits what can be represented in floating
* point (i.e., mantissa + 1 bits). So do a straight multiplication
* followed by casting. No further rounding is necessary.
*/
scale = 1.0/(double)((1ULL << src_width) - 1);
res = LLVMBuildSIToFP(builder, src, vec_type, "");
res = LLVMBuildFMul(builder, res,
lp_build_const_vec(gallivm, dst_type, scale), "");
return res;
}
else {
/*
* The source width exceeds what can be represented in floating
* point. So truncate the incoming values.
*/
mantissa = lp_mantissa(dst_type);
n = MIN2(mantissa, src_width);
n = MIN2(mantissa, src_width);
ubound = ((unsigned long long)1 << n);
mask = ubound - 1;
scale = (double)ubound/mask;
bias = (double)((unsigned long long)1 << (mantissa - n));
ubound = ((unsigned long long)1 << n);
mask = ubound - 1;
scale = (double)ubound/mask;
bias = (double)((unsigned long long)1 << (mantissa - n));
res = src;
res = src;
if (src_width > mantissa) {
int shift = src_width - mantissa;
res = LLVMBuildLShr(builder, res,
lp_build_const_int_vec(gallivm, dst_type, shift), "");
}
if(src_width > mantissa) {
int shift = src_width - mantissa;
res = LLVMBuildLShr(builder, res,
lp_build_const_int_vec(gallivm, dst_type, shift), "");
bias_ = lp_build_const_vec(gallivm, dst_type, bias);
res = LLVMBuildOr(builder,
res,
LLVMBuildBitCast(builder, bias_, int_vec_type, ""), "");
res = LLVMBuildBitCast(builder, res, vec_type, "");
res = LLVMBuildFSub(builder, res, bias_, "");
res = LLVMBuildFMul(builder, res, lp_build_const_vec(gallivm, dst_type, scale), "");
}
bias_ = lp_build_const_vec(gallivm, dst_type, bias);
res = LLVMBuildOr(builder,
res,
LLVMBuildBitCast(builder, bias_, int_vec_type, ""), "");
res = LLVMBuildBitCast(builder, res, vec_type, "");
res = LLVMBuildFSub(builder, res, bias_, "");
res = LLVMBuildFMul(builder, res, lp_build_const_vec(gallivm, dst_type, scale), "");
return res;
}