This patch will optimize the following
movq %rdi, %rax
subq %rsi, %rax
cmovsq %rsi, %rdi
movq %rdi, %rax
to
cmpq %rsi, %rdi
cmovsq %rsi, %rdi
movq %rdi, %rax
Perform this optimization if the actual result of SUB is not used.
rdar: 11540023
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158126 91177308-0d34-0410-b5e6-96231b3b80d8
The commit is intended to fix rdar://11540023.
It is implemented as part of peephole optimization. We can actually implement
this in the SelectionDAG lowering phase.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158122 91177308-0d34-0410-b5e6-96231b3b80d8
This patch will optimize the following:
sub r1, r3
cmp r3, r1 or cmp r1, r3
bge L1
TO
sub r1, r3
bge L1 or ble L1
If the branch instruction can use flag from "sub", then we can eliminate
the "cmp" instruction.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157831 91177308-0d34-0410-b5e6-96231b3b80d8
This patch will optimize the following
movq %rdi, %rax
subq %rsi, %rax
cmovsq %rsi, %rdi
movq %rdi, %rax
to
cmpq %rsi, %rdi
cmovsq %rsi, %rdi
movq %rdi, %rax
Perform this optimization if the actual result of SUB is not used.
rdar: 11540023
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157755 91177308-0d34-0410-b5e6-96231b3b80d8
to catch cases like:
%reg1024<def> = MOV r1
%reg1025<def> = MOV r0
%reg1026<def> = ADD %reg1024, %reg1025
r0 = MOV %reg1026
By commuting ADD, it let coalescer eliminate all of the copies. However, there
was a bug in the heuristics where it ended up commuting the ADD in:
%reg1024<def> = MOV r0
%reg1025<def> = MOV 0
%reg1026<def> = ADD %reg1024, %reg1025
r0 = MOV %reg1026
That did no benefit but rather ensure the last MOV would not be coalesced.
rdar://11355268
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156048 91177308-0d34-0410-b5e6-96231b3b80d8
(x > y) ? x : y
=>
(x >= y) ? x : y
So for something like
(x - y) > 0 : (x - y) ? 0
It will be
(x - y) >= 0 : (x - y) ? 0
This makes is possible to test sign-bit and eliminate a comparison against
zero. e.g.
subl %esi, %edi
testl %edi, %edi
movl $0, %eax
cmovgl %edi, %eax
=>
xorl %eax, %eax
subl %esi, $edi
cmovsl %eax, %edi
rdar://10633221
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147512 91177308-0d34-0410-b5e6-96231b3b80d8
