[llvm] r366989 - [Clang] New loop pragma vectorize_predicate

[Sjoerd Meijer via llvm-commits]

Author: sjoerdmeijer
Date: Thu Jul 25 00:33:13 2019
New Revision: 366989

URL: http://llvm.org/viewvc/llvm-project?rev=366989&view=rev
Log:
[Clang] New loop pragma vectorize_predicate

This adds a new vectorize predication loop hint:

  #pragma clang loop vectorize_predicate(enable)

that can be used to indicate to the vectoriser that all (load/store)
instructions should be predicated (masked). This allows, for example, folding
of the remainder loop into the main loop.

This patch will be followed up with D64916 and D65197. The former is a
refactoring in the loopvectorizer and the groundwork to make tail loop folding
a more general concept, and in the latter the actual tail loop folding
transformation will be implemented.

Differential Revision: https://reviews.llvm.org/D64744

Modified:
    llvm/trunk/docs/LangRef.rst

Modified: llvm/trunk/docs/LangRef.rst
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/docs/LangRef.rst?rev=366989&r1=366988&r2=366989&view=diff
==============================================================================
--- llvm/trunk/docs/LangRef.rst (original)
+++ llvm/trunk/docs/LangRef.rst Thu Jul 25 00:33:13 2019
@@ -5423,6 +5423,21 @@ is a bit. If the bit operand value is 1
    !0 = !{!"llvm.loop.vectorize.enable", i1 0}
    !1 = !{!"llvm.loop.vectorize.enable", i1 1}
 
+'``llvm.loop.vectorize.predicate.enable``' Metadata
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This metadata selectively enables or disables creating predicated instructions
+for the loop, which can enable folding of the scalar epilogue loop into the
+main loop. The first operand is the string
+``llvm.loop.vectorize.predicate.enable`` and the second operand is a bit. If
+the bit operand value is 1 vectorization is enabled. A value of 0 disables
+vectorization:
+
+.. code-block:: llvm
+
+   !0 = !{!"llvm.loop.vectorize.predicate.enable", i1 0}
+   !1 = !{!"llvm.loop.vectorize.predicate.enable", i1 1}
+
 '``llvm.loop.vectorize.width``' Metadata
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^