InstCombine: Make OptimizePointerDifference more aggressive.

- Ignore pointer casts.
- Also expand GEPs that aren't constantexprs when they have one use or only constant indices.

- We now compile "&foo[i] - &foo[j]" into "i - j".

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150961 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2012-02-20 14:34:57 +00:00
parent 6259dcdc57
commit d2348639e6
2 changed files with 53 additions and 27 deletions

View File

@@ -301,3 +301,29 @@ define i32 @test28(i32 %x, i32 %y, i32 %z) {
; CHECK-NEXT: add i32
; CHECK-NEXT: ret i32
}
define i64 @test29(i8* %foo, i64 %i, i64 %j) {
%gep1 = getelementptr inbounds i8* %foo, i64 %i
%gep2 = getelementptr inbounds i8* %foo, i64 %j
%cast1 = ptrtoint i8* %gep1 to i64
%cast2 = ptrtoint i8* %gep2 to i64
%sub = sub i64 %cast1, %cast2
ret i64 %sub
; CHECK: @test29
; CHECK-NEXT: sub i64 %i, %j
; CHECK-NEXT: ret i64
}
define i64 @test30(i8* %foo, i64 %i, i64 %j) {
%bit = bitcast i8* %foo to i32*
%gep1 = getelementptr inbounds i32* %bit, i64 %i
%gep2 = getelementptr inbounds i8* %foo, i64 %j
%cast1 = ptrtoint i32* %gep1 to i64
%cast2 = ptrtoint i8* %gep2 to i64
%sub = sub i64 %cast1, %cast2
ret i64 %sub
; CHECK: @test30
; CHECK-NEXT: %gep1.idx = shl nuw i64 %i, 2
; CHECK-NEXT: sub i64 %gep1.idx, %j
; CHECK-NEXT: ret i64
}