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llvm-project/llvm/test/Transforms/InstCombine/indexed-gep-compares.ll

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Re-commit r257064, after it was reverted in r257340. This contains a fix for the issue that caused the revert: we no longer assume that we can insert instructions after the instruction that produces the base pointer. We previously assumed that this would be ok, because the instruction produces a value and therefore is not a terminator. This is false for invoke instructions. We will now insert these new instruction directly at the location of the users. Original commit message: [InstCombine] Look through PHIs, GEPs, IntToPtrs and PtrToInts to expose more constants when comparing GEPs Summary: When comparing two GEP instructions which have the same base pointer and one of them has a constant index, it is possible to only compare indices, transforming it to a compare with a constant. This removes one use for the GEP instruction with the constant index, can reduce register pressure and can sometimes lead to removing the comparisson entirely. InstCombine was already doing this when comparing two GEPs if the base pointers were the same. However, in the case where we have complex pointer arithmetic (GEPs applied to GEPs, PHIs of GEPs, conversions to or from integers, etc) the value of the original base pointer will be hidden to the optimizer and this transformation will be disabled. This change detects when the two sides of the comparison can be expressed as GEPs with the same base pointer, even if they don't appear as such in the IR. The transformation will convert all the pointer arithmetic to arithmetic done on indices and all the relevant uses of GEPs to GEPs with a common base pointer. The GEP comparison will be converted to a comparison done on indices. Reviewers: majnemer, jmolloy Subscribers: hfinkel, jevinskie, jmolloy, aadg, llvm-commits Differential Revision: http://reviews.llvm.org/D15146 llvm-svn: 257897
2016-01-15 23:52:05 +08:00
; RUN: opt -instcombine -S < %s | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:64:64-v128:128:128-a0:0:64"
define i32 *@test1(i32* %A, i32 %Offset) {
entry:
%tmp = getelementptr inbounds i32, i32* %A, i32 %Offset
br label %bb
bb:
%RHS = phi i32* [ %RHS.next, %bb ], [ %tmp, %entry ]
%LHS = getelementptr inbounds i32, i32* %A, i32 100
%RHS.next = getelementptr inbounds i32, i32* %RHS, i64 1
%cond = icmp ult i32 * %LHS, %RHS
br i1 %cond, label %bb2, label %bb
bb2:
ret i32* %RHS
; CHECK-LABEL: @test1(
; CHECK: %[[INDEX:[0-9A-Za-z.]+]] = phi i32 [ %[[ADD:[0-9A-Za-z.]+]], %bb ], [ %Offset, %entry ]
; CHECK: %[[ADD]] = add nsw i32 %[[INDEX]], 1
; CHECK: %cond = icmp sgt i32 %[[INDEX]], 100
; CHECK: br i1 %cond, label %bb2, label %bb
; CHECK: %[[PTR:[0-9A-Za-z.]+]] = getelementptr inbounds i32, i32* %A, i32 %[[INDEX]]
; CHECK: ret i32* %[[PTR]]
}
define i32 *@test2(i32 %A, i32 %Offset) {
entry:
%A.ptr = inttoptr i32 %A to i32*
%tmp = getelementptr inbounds i32, i32* %A.ptr, i32 %Offset
br label %bb
bb:
%RHS = phi i32* [ %RHS.next, %bb ], [ %tmp, %entry ]
%LHS = getelementptr inbounds i32, i32* %A.ptr, i32 100
%RHS.next = getelementptr inbounds i32, i32* %RHS, i64 1
%cmp0 = ptrtoint i32 *%LHS to i32
%cmp1 = ptrtoint i32 *%RHS to i32
%cond = icmp ult i32 %cmp0, %cmp1
br i1 %cond, label %bb2, label %bb
bb2:
ret i32* %RHS
; CHECK-LABEL: @test2(
; CHECK: %[[INDEX:[0-9A-Za-z.]+]] = phi i32 [ %[[ADD:[0-9A-Za-z.]+]], %bb ], [ %Offset, %entry ]
; CHECK: %[[ADD]] = add nsw i32 %[[INDEX]], 1
; CHECK: %cond = icmp sgt i32 %[[INDEX]], 100
; CHECK: br i1 %cond, label %bb2, label %bb
; CHECK: %[[TOPTR:[0-9A-Za-z.]+]] = inttoptr i32 %[[ADD:[0-9A-Za-z.]+]] to i32*
; CHECK: %[[PTR:[0-9A-Za-z.]+]] = getelementptr inbounds i32, i32* %[[TOPTR]], i32 %[[INDEX]]
; CHECK: ret i32* %[[PTR]]
}
; Perform the transformation only if we know that the GEPs used are inbounds.
define i32 *@test3(i32* %A, i32 %Offset) {
entry:
%tmp = getelementptr i32, i32* %A, i32 %Offset
br label %bb
bb:
%RHS = phi i32* [ %RHS.next, %bb ], [ %tmp, %entry ]
%LHS = getelementptr i32, i32* %A, i32 100
%RHS.next = getelementptr i32, i32* %RHS, i64 1
%cond = icmp ult i32 * %LHS, %RHS
br i1 %cond, label %bb2, label %bb
bb2:
ret i32* %RHS
; CHECK-LABEL: @test3(
; CHECK-NOT: %cond = icmp sgt i32 %{{[0-9A-Za-z.]+}}, 100
}
; An inttoptr that requires an extension or truncation will be opaque when determining
; the base pointer. In this case we can still perform the transformation by considering
; A.ptr as being the base pointer.
define i32 *@test4(i16 %A, i32 %Offset) {
entry:
%A.ptr = inttoptr i16 %A to i32*
%tmp = getelementptr inbounds i32, i32* %A.ptr, i32 %Offset
br label %bb
bb:
%RHS = phi i32* [ %RHS.next, %bb ], [ %tmp, %entry ]
%LHS = getelementptr inbounds i32, i32* %A.ptr, i32 100
%RHS.next = getelementptr inbounds i32, i32* %RHS, i64 1
%cmp0 = ptrtoint i32 *%LHS to i32
%cmp1 = ptrtoint i32 *%RHS to i32
%cond = icmp ult i32 %cmp0, %cmp1
br i1 %cond, label %bb2, label %bb
bb2:
ret i32* %RHS
; CHECK-LABEL: @test4(
; CHECK: %cond = icmp sgt i32 %{{[0-9A-Za-z.]+}}, 100
}
declare i32* @fun_ptr()
define i32 *@test5(i32 %Offset) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
entry:
%A = invoke i32 *@fun_ptr() to label %cont unwind label %lpad
cont:
%tmp = getelementptr inbounds i32, i32* %A, i32 %Offset
br label %bb
bb:
%RHS = phi i32* [ %RHS.next, %bb ], [ %tmp, %cont ]
%LHS = getelementptr inbounds i32, i32* %A, i32 100
%RHS.next = getelementptr inbounds i32, i32* %RHS, i64 1
%cond = icmp ult i32 * %LHS, %RHS
br i1 %cond, label %bb2, label %bb
bb2:
ret i32* %RHS
lpad:
%l = landingpad { i8*, i32 } cleanup
ret i32* null
; CHECK-LABEL: @test5(
; CHECK: %[[INDEX:[0-9A-Za-z.]+]] = phi i32 [ %[[ADD:[0-9A-Za-z.]+]], %bb ], [ %Offset, %cont ]
; CHECK: %[[ADD]] = add nsw i32 %[[INDEX]], 1
; CHECK: %cond = icmp sgt i32 %[[INDEX]], 100
; CHECK: br i1 %cond, label %bb2, label %bb
; CHECK: %[[PTR:[0-9A-Za-z.]+]] = getelementptr inbounds i32, i32* %A, i32 %[[INDEX]]
; CHECK: ret i32* %[[PTR]]
}
declare i32 @fun_i32()
define i32 *@test6(i32 %Offset) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
entry:
%A = invoke i32 @fun_i32() to label %cont unwind label %lpad
cont:
%A.ptr = inttoptr i32 %A to i32*
%tmp = getelementptr inbounds i32, i32* %A.ptr, i32 %Offset
br label %bb
bb:
%RHS = phi i32* [ %RHS.next, %bb ], [ %tmp, %cont ]
%LHS = getelementptr inbounds i32, i32* %A.ptr, i32 100
%RHS.next = getelementptr inbounds i32, i32* %RHS, i64 1
%cond = icmp ult i32 * %LHS, %RHS
br i1 %cond, label %bb2, label %bb
bb2:
ret i32* %RHS
lpad:
%l = landingpad { i8*, i32 } cleanup
ret i32* null
; CHECK-LABEL: @test6(
; CHECK: %[[INDEX:[0-9A-Za-z.]+]] = phi i32 [ %[[ADD:[0-9A-Za-z.]+]], %bb ], [ %Offset, %cont ]
; CHECK: %[[ADD]] = add nsw i32 %[[INDEX]], 1
; CHECK: %cond = icmp sgt i32 %[[INDEX]], 100
; CHECK: br i1 %cond, label %bb2, label %bb
; CHECK: %[[TOPTR:[0-9A-Za-z.]+]] = inttoptr i32 %[[ADD:[0-9A-Za-z.]+]] to i32*
; CHECK: %[[PTR:[0-9A-Za-z.]+]] = getelementptr inbounds i32, i32* %[[TOPTR]], i32 %[[INDEX]]
; CHECK: ret i32* %[[PTR]]
}
[InstCombine] Do not RAUW a constant GEP canRewriteGEPAsOffset expects to process instructions, not constants. This fixes PR30342. llvm-svn: 281650
2016-09-16 04:10:09 +08:00
@pr30402 = constant i64 3
define i1 @test7() {
entry:
br label %bb7
bb7: ; preds = %bb10, %entry-block
%phi = phi i64* [ @pr30402, %entry ], [ getelementptr inbounds (i64, i64* @pr30402, i32 1), %bb7 ]
%cmp = icmp eq i64* %phi, getelementptr inbounds (i64, i64* @pr30402, i32 1)
br i1 %cmp, label %bb10, label %bb7
bb10:
ret i1 %cmp
}
; CHECK-LABEL: @test7(
; CHECK: %[[phi:.*]] = phi i64* [ @pr30402, %entry ], [ getelementptr inbounds (i64, i64* @pr30402, i32 1), %bb7 ]
; CHECK: %[[cmp:.*]] = icmp eq i64* %[[phi]], getelementptr inbounds (i64, i64* @pr30402, i32 1)
; CHECK: ret i1 %[[cmp]]
Re-commit r257064, after it was reverted in r257340. This contains a fix for the issue that caused the revert: we no longer assume that we can insert instructions after the instruction that produces the base pointer. We previously assumed that this would be ok, because the instruction produces a value and therefore is not a terminator. This is false for invoke instructions. We will now insert these new instruction directly at the location of the users. Original commit message: [InstCombine] Look through PHIs, GEPs, IntToPtrs and PtrToInts to expose more constants when comparing GEPs Summary: When comparing two GEP instructions which have the same base pointer and one of them has a constant index, it is possible to only compare indices, transforming it to a compare with a constant. This removes one use for the GEP instruction with the constant index, can reduce register pressure and can sometimes lead to removing the comparisson entirely. InstCombine was already doing this when comparing two GEPs if the base pointers were the same. However, in the case where we have complex pointer arithmetic (GEPs applied to GEPs, PHIs of GEPs, conversions to or from integers, etc) the value of the original base pointer will be hidden to the optimizer and this transformation will be disabled. This change detects when the two sides of the comparison can be expressed as GEPs with the same base pointer, even if they don't appear as such in the IR. The transformation will convert all the pointer arithmetic to arithmetic done on indices and all the relevant uses of GEPs to GEPs with a common base pointer. The GEP comparison will be converted to a comparison done on indices. Reviewers: majnemer, jmolloy Subscribers: hfinkel, jevinskie, jmolloy, aadg, llvm-commits Differential Revision: http://reviews.llvm.org/D15146 llvm-svn: 257897
2016-01-15 23:52:05 +08:00
declare i32 @__gxx_personality_v0(...)
[InstCombine] Make sure that LHS and RHS have the same type in transformToIndexedCompare If they don't have the same type, the size of the constant index would need to be adjusted (and this wouldn't be always possible). Alternatively we could try the analysis with the initial RHS value, which would guarantee that the two sides have the same type. However it is unlikely that in practice this would pass our transformation requirements. Fixes PR31808 (https://llvm.org/bugs/show_bug.cgi?id=31808). llvm-svn: 293629
2017-01-31 22:04:15 +08:00
define i1 @test8(i64* %in, i64 %offset) {
entry:
%ld = load i64, i64* %in, align 8
%casti8 = inttoptr i64 %ld to i8*
%gepi8 = getelementptr inbounds i8, i8* %casti8, i64 %offset
%cast = bitcast i8* %gepi8 to i32**
%ptrcast = inttoptr i64 %ld to i32**
%gepi32 = getelementptr inbounds i32*, i32** %ptrcast, i64 1
%cmp = icmp eq i32** %gepi32, %cast
ret i1 %cmp
; CHECK-LABEL: @test8(
; CHECK-NOT: icmp eq i32 %{{[0-9A-Za-z.]+}}, 1
}