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| author | Andrew Waterman <andrew@sifive.com> | 2017-02-15 12:33:42 -0800 |
|---|---|---|
| committer | Andrew Waterman <andrew@sifive.com> | 2017-02-15 12:33:42 -0800 |
| commit | 1efca13c0b75caa358a86a00a62fad77556acefe (patch) | |
| tree | 3330aeeed5a897df1e654b60ac8b03a60127f368 /src | |
| parent | aa0915932e79278ab63352713792a7a5e120b33e (diff) | |
| download | riscv-isa-manual-1efca13c0b75caa358a86a00a62fad77556acefe.zip riscv-isa-manual-1efca13c0b75caa358a86a00a62fad77556acefe.tar.gz riscv-isa-manual-1efca13c0b75caa358a86a00a62fad77556acefe.tar.bz2 | |
Add signed array bounds comparison note
Diffstat (limited to 'src')
| -rw-r--r-- | src/rv32.tex | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/src/rv32.tex b/src/rv32.tex index bc84ac5..c1571ae 100644 --- a/src/rv32.tex +++ b/src/rv32.tex @@ -788,6 +788,11 @@ using signed and unsigned comparison respectively. Note, BGT, BGTU, BLE, and BLEU can be synthesized by reversing the operands to BLT, BLTU, BGE, and BGEU, respectively. +\begin{commentary} +Signed array bounds may be checked with a single BLTU instruction, since +any negative index will compare greater than any nonnegative bound. +\end{commentary} + Software should be optimized such that the sequential code path is the most common path, with less-frequently taken code paths placed out of line. Software should also assume that backward branches will be |