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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| clang | ||
| clang-tools-extra | ||
| compiler-rt | ||
| debuginfo-tests | ||
| libclc | ||
| libcxx | ||
| libcxxabi | ||
| libunwind | ||
| lld | ||
| lldb | ||
| llgo | ||
| llvm | ||
| openmp | ||
| parallel-libs | ||
| polly | ||