https://bugs.kde.org/show_bug.cgi?id=506211
Bug ID: 506211
Summary: Constant folding improvements
Classification: Developer tools
Product: valgrind
Version First unspecified
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: vex
Assignee: jsew...@acm.org
Reporter: flo2...@eich-krohm.de
Target Milestone: ---
Created attachment 182684
--> https://bugs.kde.org/attachment.cgi?id=182684&action=edit
audit of constant folding and algebraic simplification
Are there missed constant folding opportunities in VEX ir_opt.c? Yes.
Attached is a spreadsheet that shows the status of constant folding and
algebraic simplification for IROps that have integer operands and results.
Function fold_Expr_WRK is the work horse. There are also fold_IRExpr_Binop and
fold_IRExpr_Unop. I did not look at those.
Here's the plan:
1) Write iropt-test similar to vbit-test using the IR injection machinery to
verify that constant folding works as expected.
2) Verify existing constant folding :)
3) Fill in the constant folding gaps running iropt-test alongside.
4) Explore whether IR injection can be extended to allow symbolic verification
of algebraic simplifications.
E.g. verify that Iop_And32(x, 0) --> x without assigning selected constants
to x thereby transforming the issue to constant folding (and having only
partial coverage).
Current status: initial version of iropt-test verified that constant folding
for Iop_Not8 works :)
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