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Unified Diff: native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst

Issue 419803005: PNaCl documentation: clarify vector alignment, and update navigation (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Revert weird edit. Created 6 years, 5 months ago
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Index: native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
diff --git a/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst b/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
index af1ff310aac107c8fcb62388389ce1316511a228..1605349eadf5bcd42a5053eb2c249fd1fcc772d0 100644
--- a/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
+++ b/native_client_sdk/src/doc/reference/pnacl-c-cpp-language-support.rst
@@ -215,9 +215,9 @@ of SIMD vector datatypes and operations which map well to modern
architectures and offer performance which matches or approaches
hardware-specific uses.
-SIMD vector support was added to Portable Native Client for version 37
-of Chrome and more features, including performance enhancements, are
-expected to be added in subsequent releases.
+SIMD vector support was added to Portable Native Client for version 37 of Chrome
+and more features, including performance enhancements, have been added in
binji 2014/07/26 00:24:08 this is vague. Which version were the enhancements
JF 2014/07/28 16:36:58 Done.
+subsequent releases.
Hand-Coding Vector Extensions
-----------------------------
@@ -254,20 +254,22 @@ elements of all ``0`` or all ``1``:
return ret;
}
-Vector datatypes are currently expected to be 128-bit wide with one of
-the following element types:
-
-============ ============ ================
-Type Num Elements Vector Bit Width
-============ ============ ================
-``uint8_t`` 16 128
-``int8_t`` 16 128
-``uint16_t`` 8 128
-``int16_t`` 8 128
-``uint32_t`` 4 128
-``int32_t`` 4 128
-``float`` 4 128
-============ ============ ================
+Vector datatypes are currently expected to be 128-bit wide with one of the
+following element types, and they're expected to be alignment to the underlying
binji 2014/07/26 00:24:08 s/alignment/aligned/
JF 2014/07/28 16:36:58 Done.
+element's bit width (loads and store will otherwise be broken up into scalar
+accesses to prevent faults):
+
+============ ============ ================ ======================
+Type Num Elements Vector Bit Width Expected Bit Alignment
+============ ============ ================ ======================
+``uint8_t`` 16 128 8
+``int8_t`` 16 128 8
+``uint16_t`` 8 128 16
+``int16_t`` 8 128 16
+``uint32_t`` 4 128 32
+``int32_t`` 4 128 32
+``float`` 4 128 32
+============ ============ ================ ======================
64-bit integers and double-precision floating point will be supported in
a future release, as will 256-bit and 512-bit vectors.
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