forked from OSchip/llvm-project
c1d5955684
Summary: On behalf of julia.koval@intel.com The patch transforms canonical version of unsigned saturation, which is sub(max(a,b),a) or sub(a,min(a,b)) to special psubus insturuction on targets, which support it(8bit and 16bit uints). umax(a,b) - b -> subus(a,b) a - umin(a,b) -> subus(a,b) There is also extra case handled, when right part of sub is 32 bit and can be truncated, using UMIN(this transformation was discussed in https://reviews.llvm.org/D25987). The example of special case code: ``` void foo(unsigned short *p, int max, int n) { int i; unsigned m; for (i = 0; i < n; i++) { m = *--p; *p = (unsigned short)(m >= max ? m-max : 0); } } ``` Max in this example is truncated to max_short value, if it is greater than m, or just truncated to 16 bit, if it is not. It is vaid transformation, because if max > max_short, result of the expression will be zero. Here is the table of types, I try to support, special case items are bold: | Size | 128 | 256 | 512 | ----- | ----- | ----- | ----- | i8 | v16i8 | v32i8 | v64i8 | i16 | v8i16 | v16i16 | v32i16 | i32 | | **v8i32** | **v16i32** | i64 | | | **v8i64** Reviewers: zvi, spatel, DavidKreitzer, RKSimon Reviewed By: zvi Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D37534 llvm-svn: 315237 |
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| LLVMBuild.txt | ||
| README.txt | ||
| RELEASE_TESTERS.TXT | ||
| configure | ||
| llvm.spec.in | ||
README.txt
Low Level Virtual Machine (LLVM) ================================ This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments. LLVM is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. Please see the documentation provided in docs/ for further assistance with LLVM, and in particular docs/GettingStarted.rst for getting started with LLVM and docs/README.txt for an overview of LLVM's documentation setup. If you are writing a package for LLVM, see docs/Packaging.rst for our suggestions.