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llvm-mirror/test/Transforms/InstCombine/load-bitcast64.ll
Roman Lebedev 794d4b6ead [InstCombine] combineLoadToOperationType(): don't fold int<->ptr cast into load
And another step towards transforms not introducing inttoptr and/or
ptrtoint casts that weren't there already.

As we've been establishing (see D88788/D88789), if there is a int<->ptr cast,
it basically must stay as-is, we can't do much with it.

I've looked, and the most source of new such casts being introduces,
as far as i can tell, is this transform, which, ironically,
tries to reduce count of casts..

On vanilla llvm test-suite + RawSpeed, @ `-O3`, this results in
-33.58% less `IntToPtr`s (19014 -> 12629)
and +76.20% more `PtrToInt`s (18589 -> 32753),
which is an increase of +20.69% in total.

However just on RawSpeed, where i know there are basically
none `IntToPtr` in the original source code,
this results in -99.27% less `IntToPtr`s (2724 -> 20)
and +82.92% more `PtrToInt`s (4513 -> 8255).
which is again an increase of 14.34% in total.

To me this does seem like the step in the right direction,
we end up with strictly less `IntToPtr`, but strictly more `PtrToInt`,
which seems like a reasonable trade-off.

See https://reviews.llvm.org/D88860 / https://reviews.llvm.org/D88995
for some more discussion on the subject.

(Eventually, `CastInst::isNoopCast()`/`CastInst::isEliminableCastPair`
should be taught about this, yes)

Reviewed By: nlopes, nikic

Differential Revision: https://reviews.llvm.org/D88979
2020-10-11 20:24:28 +03:00

106 lines
2.6 KiB
LLVM

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -instcombine -S < %s | FileCheck %s
target datalayout = "p:64:64:64-i64:32:32"
define i64* @test1(i8* %x) {
; CHECK-LABEL: @test1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = bitcast i8* [[X:%.*]] to i64*
; CHECK-NEXT: [[B:%.*]] = load i64, i64* [[A]], align 4
; CHECK-NEXT: [[C:%.*]] = inttoptr i64 [[B]] to i64*
; CHECK-NEXT: ret i64* [[C]]
;
entry:
%a = bitcast i8* %x to i64*
%b = load i64, i64* %a
%c = inttoptr i64 %b to i64*
ret i64* %c
}
define i32* @test2(i8* %x) {
; CHECK-LABEL: @test2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = bitcast i8* [[X:%.*]] to i32*
; CHECK-NEXT: [[B:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: [[TMP0:%.*]] = zext i32 [[B]] to i64
; CHECK-NEXT: [[C:%.*]] = inttoptr i64 [[TMP0]] to i32*
; CHECK-NEXT: ret i32* [[C]]
;
entry:
%a = bitcast i8* %x to i32*
%b = load i32, i32* %a
%c = inttoptr i32 %b to i32*
ret i32* %c
}
define i64* @test3(i8* %x) {
; CHECK-LABEL: @test3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = bitcast i8* [[X:%.*]] to i32*
; CHECK-NEXT: [[B:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: [[TMP0:%.*]] = zext i32 [[B]] to i64
; CHECK-NEXT: [[C:%.*]] = inttoptr i64 [[TMP0]] to i64*
; CHECK-NEXT: ret i64* [[C]]
;
entry:
%a = bitcast i8* %x to i32*
%b = load i32, i32* %a
%c = inttoptr i32 %b to i64*
ret i64* %c
}
define i64 @test4(i8* %x) {
; CHECK-LABEL: @test4(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = bitcast i8* [[X:%.*]] to i64**
; CHECK-NEXT: [[B:%.*]] = load i64*, i64** [[A]], align 8
; CHECK-NEXT: [[C:%.*]] = ptrtoint i64* [[B]] to i64
; CHECK-NEXT: ret i64 [[C]]
;
entry:
%a = bitcast i8* %x to i64**
%b = load i64*, i64** %a
%c = ptrtoint i64* %b to i64
ret i64 %c
}
define i32 @test5(i8* %x) {
; CHECK-LABEL: @test5(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = bitcast i8* [[X:%.*]] to i32**
; CHECK-NEXT: [[B:%.*]] = load i32*, i32** [[A]], align 8
; CHECK-NEXT: [[TMP0:%.*]] = ptrtoint i32* [[B]] to i64
; CHECK-NEXT: [[C:%.*]] = trunc i64 [[TMP0]] to i32
; CHECK-NEXT: ret i32 [[C]]
;
entry:
%a = bitcast i8* %x to i32**
%b = load i32*, i32** %a
%c = ptrtoint i32* %b to i32
ret i32 %c
}
define i64 @test6(i8* %x) {
; CHECK-LABEL: @test6(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = bitcast i8* [[X:%.*]] to i32**
; CHECK-NEXT: [[B:%.*]] = load i32*, i32** [[A]], align 8
; CHECK-NEXT: [[C:%.*]] = ptrtoint i32* [[B]] to i64
; CHECK-NEXT: ret i64 [[C]]
;
entry:
%a = bitcast i8* %x to i32**
%b = load i32*, i32** %a
%c = ptrtoint i32* %b to i64
ret i64 %c
}