RPCSX/llvm
1
0
Fork 0
mirror of https://github.com/RPCSX/llvm.git synced 2024-12-03 17:31:50 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Simplify x >=u x >> y and x >=u x udiv y

Browse Source 
Summary:
Extends InstSimplify to handle both `x >=u x >> y` and `x >=u x udiv y`.

This is a folloup of rL258422 and
https://github.com/rust-lang/rust/pull/30917 where llvm failed to
optimize away the bounds checking in a binary search.

Patch by Arthur Silva!

Reviewers: sanjoy

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25941

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285228 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das 2016-10-26 19:18:43 +00:00
parent 5a50eb6b58
commit cf6e9a81f6
2 changed files with 43 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
lib/Analysis/InstructionSimplify.cpp
View File

@ -2857,6 +2857,17 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
return getTrue(ITy);
}
// x >=u x >> y
// x >=u x udiv y.
if (RBO && (match(RBO, m_LShr(m_Specific(LHS), m_Value())) ||
match(RBO, m_UDiv(m_Specific(LHS), m_Value())))) {
// icmp pred X, (X op Y)
if (Pred == ICmpInst::ICMP_ULT)
return getFalse(ITy);
if (Pred == ICmpInst::ICMP_UGE)
return getTrue(ITy);
}
// handle:
// CI2 << X == CI
// CI2 << X != CI

32
test/Transforms/InstSimplify/compare.ll
View File

@ -409,6 +409,22 @@ define i1 @lshr5(i32 %X, i32 %Y) {
; CHECK: ret i1 false
}
define i1 @lshr6(i32 %X, i32 %Y) {
; CHECK-LABEL: @lshr6(
%A = lshr i32 %X, %Y
%C = icmp ult i32 %X, %A
ret i1 %C
; CHECK: ret i1 false
}
define i1 @lshr7(i32 %X, i32 %Y) {
; CHECK-LABEL: @lshr7(
%A = lshr i32 %X, %Y
%C = icmp uge i32 %X, %A
ret i1 %C
; CHECK: ret i1 true
}
define i1 @ashr1(i32 %x) {
; CHECK-LABEL: @ashr1(
%s = ashr i32 -1, %x
@ -583,6 +599,22 @@ define i1 @udiv6(i32 %X) nounwind {
; CHECK: ret i1 %C
}
define i1 @udiv7(i32 %X, i32 %Y) {
; CHECK-LABEL: @udiv7(
%A = udiv i32 %X, %Y
%C = icmp ult i32 %X, %A
ret i1 %C
; CHECK: ret i1 false
}
define i1 @udiv8(i32 %X, i32 %Y) {
; CHECK-LABEL: @udiv8(
%A = udiv i32 %X, %Y
%C = icmp uge i32 %X, %A
ret i1 %C
; CHECK: ret i1 true
}
define i1 @mul1(i32 %X) {
; CHECK-LABEL: @mul1(
; Square of a non-zero number is non-zero if there is no overflow.