[llvm] 2ede5dc - [DOC] Remove too strong restriction for ‘llvm.experimental.gc.statepoint’ Intrinsic

[Serguei Katkov via llvm-commits]

Author: Serguei Katkov
Date: 2020-04-02T10:56:42+07:00
New Revision: 2ede5dccffa5f62d3f13eca603bc3ad0e73b7514

URL: https://github.com/llvm/llvm-project/commit/2ede5dccffa5f62d3f13eca603bc3ad0e73b7514
DIFF: https://github.com/llvm/llvm-project/commit/2ede5dccffa5f62d3f13eca603bc3ad0e73b7514.diff

LOG: [DOC] Remove too strong restriction for ‘llvm.experimental.gc.statepoint’ Intrinsic

The requirement for deopt parameter to be in gc parameter if it can
be modified by GC is very strong and difficult to follow.

The key example of why this can't work:
%p1 = bitcast i8* %p to i8*
statepoint [gc = (%p1)], [deopt = (%p1)]

The optimizer is allowed to replace either use (or both) of %p1 with %p.
If it updates only one of the two (entirely legal), the two sets do not overlap.

So this change removes the strong wording.

Reviewers: reames, dantrushin
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D77122

Added: 
    

Modified: 
    llvm/docs/Statepoints.rst

Removed: 
    


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diff  --git a/llvm/docs/Statepoints.rst b/llvm/docs/Statepoints.rst
index 3832a43b287e..5d6033bc50a7 100644
--- a/llvm/docs/Statepoints.rst
+++ b/llvm/docs/Statepoints.rst
@@ -522,11 +522,8 @@ of the callee. The '# transition args' field indicates how many operands
 are to be interpreted as 'transition parameters'.
 
 The 'deopt parameters' arguments contain an arbitrary list of Values
-which is meaningful to the runtime.  The runtime may read any of these
-values, but is assumed not to modify them.  If the garbage collector
-might need to modify one of these values, it must also be listed in
-the 'gc pointer' argument list.  The '# deopt args' field indicates
-how many operands are to be interpreted as 'deopt parameters'.
+which is meaningful to the runtime.  The '# deopt args' field
+indicates how many operands are to be interpreted as 'deopt parameters'.
 
 The 'gc parameters' arguments contain every pointer to a garbage
 collector object which potentially needs to be updated by the garbage