https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88784
Bug ID: 88784
Summary: Middle end is missing some optimizations about
unsigned
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: helijia at gcc dot gnu.org
Target Milestone: ---
For both operands are unsigned, the following optimizations are valid, and
missing:
1. X > Y && X != 0 --> X > Y
2. X > Y || X != 0 --> X != 0
3. X <= Y || X != 0 --> true
4. X <= Y || X == 0 --> X <= Y
5. X > Y && X == 0 --> false
unsigned foo(unsigned x, unsigned y) { return x > y && x != 0; }
should fold to x > y, but I found we haven't done it right now.
I compile the code with the following command.
g++ unsigned.cpp -Ofast -c -S -o unsigned.s -fdump-tree-all
