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clang-p2996/llvm/test/Transforms/InstCombine/load.ll
Nikita Popov 90ba33099c [InstCombine] Canonicalize constant GEPs to i8 source element type (#68882) 
This patch canonicalizes getelementptr instructions with constant
indices to use the `i8` source element type. This makes it easier for
optimizations to recognize that two GEPs are identical, because they
don't need to see past many different ways to express the same offset.

This is a first step towards
https://discourse.llvm.org/t/rfc-replacing-getelementptr-with-ptradd/68699.
This is limited to constant GEPs only for now, as they have a clear
canonical form, while we're not yet sure how exactly to deal with
variable indices.

The test llvm/test/Transforms/PhaseOrdering/switch_with_geps.ll gives
two representative examples of the kind of optimization improvement we
expect from this change. In the first test SimplifyCFG can now realize
that all switch branches are actually the same. In the second test it
can convert it into simple arithmetic. These are representative of
common optimization failures we see in Rust.

Fixes https://github.com/llvm/llvm-project/issues/69841.
2024-01-24 15:25:29 +01:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -passes=instcombine -S < %s | FileCheck %s
target datalayout = "e-m:e-p:64:64:64-i64:64-f80:128-n8:16:32:64-S128-ni:1"
@X = constant i32 42 ; <ptr> [#uses=2]
@X2 = constant i32 47 ; <ptr> [#uses=1]
@Y = constant [2 x { i32, float }] [ { i32, float } { i32 12, float 1.000000e+00 }, { i32, float } { i32 37, float 0x3FF3B2FEC0000000 } ] ; <ptr> [#uses=2]
@Z = constant [2 x { i32, float }] zeroinitializer ; <ptr> [#uses=1]
@GLOBAL = internal constant [4 x i32] zeroinitializer
define i32 @test1() {
; CHECK-LABEL: @test1(
; CHECK-NEXT: ret i32 42
;
%B = load i32, ptr @X ; <i32> [#uses=1]
ret i32 %B
}
define float @test2() {
; CHECK-LABEL: @test2(
; CHECK-NEXT: ret float 0x3FF3B2FEC0000000
;
%A = getelementptr [2 x { i32, float }], ptr @Y, i64 0, i64 1, i32 1 ; <ptr> [#uses=1]
%B = load float, ptr %A ; <float> [#uses=1]
ret float %B
}
define i32 @test3() {
; CHECK-LABEL: @test3(
; CHECK-NEXT: ret i32 12
;
%A = getelementptr [2 x { i32, float }], ptr @Y, i64 0, i64 0, i32 0 ; <ptr> [#uses=1]
%B = load i32, ptr %A ; <i32> [#uses=1]
ret i32 %B
}
define i32 @test4() {
; CHECK-LABEL: @test4(
; CHECK-NEXT: ret i32 0
;
%A = getelementptr [2 x { i32, float }], ptr @Z, i64 0, i64 1, i32 0 ; <ptr> [#uses=1]
%B = load i32, ptr %A ; <i32> [#uses=1]
ret i32 %B
}
define i32 @test5(i1 %C) {
; CHECK-LABEL: @test5(
; CHECK-NEXT: [[Z:%.*]] = select i1 [[C:%.*]], i32 42, i32 47
; CHECK-NEXT: ret i32 [[Z]]
;
%Y = select i1 %C, ptr @X, ptr @X2 ; <ptr> [#uses=1]
%Z = load i32, ptr %Y ; <i32> [#uses=1]
ret i32 %Z
}
define i32 @load_gep_null_inbounds(i64 %X) {
; CHECK-LABEL: @load_gep_null_inbounds(
; CHECK-NEXT: store i1 true, ptr poison, align 1
; CHECK-NEXT: ret i32 poison
;
%V = getelementptr inbounds i32, ptr null, i64 %X
%R = load i32, ptr %V
ret i32 %R
}
define i32 @load_gep_null_not_inbounds(i64 %X) {
; CHECK-LABEL: @load_gep_null_not_inbounds(
; CHECK-NEXT: store i1 true, ptr poison, align 1
; CHECK-NEXT: ret i32 poison
;
%V = getelementptr i32, ptr null, i64 %X
%R = load i32, ptr %V
ret i32 %R
}
define i32 @test7_no_null_opt(i32 %X) #0 {
; CHECK-LABEL: @test7_no_null_opt(
; CHECK-NEXT: [[TMP1:%.*]] = sext i32 [[X:%.*]] to i64
; CHECK-NEXT: [[V:%.*]] = getelementptr i32, ptr null, i64 [[TMP1]]
; CHECK-NEXT: [[R:%.*]] = load i32, ptr [[V]], align 4
; CHECK-NEXT: ret i32 [[R]]
;
%V = getelementptr i32, ptr null, i32 %X ; <ptr> [#uses=1]
%R = load i32, ptr %V ; <i32> [#uses=1]
ret i32 %R
}
attributes #0 = { null_pointer_is_valid }
define i32 @test8(ptr %P) {
; CHECK-LABEL: @test8(
; CHECK-NEXT: store i32 1, ptr [[P:%.*]], align 4
; CHECK-NEXT: ret i32 1
;
store i32 1, ptr %P
%X = load i32, ptr %P ; <i32> [#uses=1]
ret i32 %X
}
define i32 @test9(ptr %P) {
; CHECK-LABEL: @test9(
; CHECK-NEXT: ret i32 0
;
%X = load i32, ptr %P ; <i32> [#uses=1]
%Y = load i32, ptr %P ; <i32> [#uses=1]
%Z = sub i32 %X, %Y ; <i32> [#uses=1]
ret i32 %Z
}
define i32 @test10(i1 %C.upgrd.1, ptr %P, ptr %Q) {
; CHECK-LABEL: @test10(
; CHECK-NEXT: br i1 [[C_UPGRD_1:%.*]], label [[T:%.*]], label [[F:%.*]]
; CHECK: T:
; CHECK-NEXT: store i32 1, ptr [[Q:%.*]], align 4
; CHECK-NEXT: br label [[C:%.*]]
; CHECK: F:
; CHECK-NEXT: br label [[C]]
; CHECK: C:
; CHECK-NEXT: store i32 0, ptr [[P:%.*]], align 4
; CHECK-NEXT: ret i32 0
;
br i1 %C.upgrd.1, label %T, label %F
T: ; preds = %0
store i32 1, ptr %Q
store i32 0, ptr %P
br label %C
F: ; preds = %0
store i32 0, ptr %P
br label %C
C: ; preds = %F, %T
%V = load i32, ptr %P ; <i32> [#uses=1]
ret i32 %V
}
define double @test11(ptr %p) {
; CHECK-LABEL: @test11(
; CHECK-NEXT: [[T0:%.*]] = getelementptr i8, ptr [[P:%.*]], i64 8
; CHECK-NEXT: store double 2.000000e+00, ptr [[T0]], align 8
; CHECK-NEXT: ret double 2.000000e+00
;
%t0 = getelementptr double, ptr %p, i32 1
store double 2.0, ptr %t0
%t1 = getelementptr double, ptr %p, i32 1
%x = load double, ptr %t1
ret double %x
}
define i32 @test12(ptr %P) {
; CHECK-LABEL: @test12(
; CHECK-NEXT: ret i32 123
;
%A = alloca i32
store i32 123, ptr %A
; Cast the result of the load not the source
%V = load i32, ptr %A
ret i32 %V
}
define <16 x i8> @test13(<2 x i64> %x) {
; CHECK-LABEL: @test13(
; CHECK-NEXT: ret <16 x i8> zeroinitializer
;
%tmp = load <16 x i8>, ptr @GLOBAL
ret <16 x i8> %tmp
}
; This test must not have the store of %x forwarded to the load -- there is an
; intervening store if %y. However, the intervening store occurs with a different
; type and size and to a different pointer value. This is ensuring that none of
; those confuse the analysis into thinking that the second store does not alias
; the first.
define i8 @test14(i8 %x, i32 %y) {
; CHECK-LABEL: @test14(
; CHECK-NEXT: [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT: store i8 [[X:%.*]], ptr [[A]], align 1
; CHECK-NEXT: store i32 [[Y:%.*]], ptr [[A]], align 4
; CHECK-NEXT: [[R:%.*]] = load i8, ptr [[A]], align 1
; CHECK-NEXT: ret i8 [[R]]
;
%a = alloca i32
store i8 %x, ptr %a
store i32 %y, ptr %a
%r = load i8, ptr %a
ret i8 %r
}
@test15_global = external global i32
; Same test as @test14 essentially, but using a global instead of an alloca.
define i8 @test15(i8 %x, i32 %y) {
; CHECK-LABEL: @test15(
; CHECK-NEXT: store i8 [[X:%.*]], ptr @test15_global, align 1
; CHECK-NEXT: store i32 [[Y:%.*]], ptr @test15_global, align 4
; CHECK-NEXT: [[R:%.*]] = load i8, ptr @test15_global, align 1
; CHECK-NEXT: ret i8 [[R]]
;
store i8 %x, ptr @test15_global
store i32 %y, ptr @test15_global
%r = load i8, ptr @test15_global
ret i8 %r
}
; Check that we canonicalize loads which are only stored to use integer types
; when there is a valid integer type.
define void @test16(ptr %x, ptr %a, ptr %b, ptr %c) {
; CHECK-LABEL: @test16(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X1:%.*]] = load float, ptr [[X:%.*]], align 4
; CHECK-NEXT: store float [[X1]], ptr [[A:%.*]], align 4
; CHECK-NEXT: store float [[X1]], ptr [[B:%.*]], align 4
; CHECK-NEXT: [[X2:%.*]] = load float, ptr [[X]], align 4
; CHECK-NEXT: store float [[X2]], ptr [[B]], align 4
; CHECK-NEXT: store float [[X2]], ptr [[C:%.*]], align 4
; CHECK-NEXT: ret void
;
entry:
%x1 = load float, ptr %x
store float %x1, ptr %a
store float %x1, ptr %b
%x2 = load float, ptr %x
store float %x2, ptr %b
%x2.cast = bitcast float %x2 to i32
store i32 %x2.cast, ptr %c
ret void
}
define void @test16-vect(ptr %x, ptr %a, ptr %b, ptr %c) {
; CHECK-LABEL: @test16-vect(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X1:%.*]] = load <4 x i8>, ptr [[X:%.*]], align 4
; CHECK-NEXT: store <4 x i8> [[X1]], ptr [[A:%.*]], align 4
; CHECK-NEXT: store <4 x i8> [[X1]], ptr [[B:%.*]], align 4
; CHECK-NEXT: [[X2:%.*]] = load <4 x i8>, ptr [[X]], align 4
; CHECK-NEXT: store <4 x i8> [[X2]], ptr [[B]], align 4
; CHECK-NEXT: store <4 x i8> [[X2]], ptr [[C:%.*]], align 4
; CHECK-NEXT: ret void
;
entry:
%x1 = load <4 x i8>, ptr %x
store <4 x i8> %x1, ptr %a
store <4 x i8> %x1, ptr %b
%x2 = load <4 x i8>, ptr %x
store <4 x i8> %x2, ptr %b
%x2.cast = bitcast <4 x i8> %x2 to i32
store i32 %x2.cast, ptr %c
ret void
}
; Check that in cases similar to @test16 we don't try to rewrite a load when
; its only use is a store but it is used as the pointer to that store rather
; than the value.
define void @test17(ptr %x, i8 %y) {
; CHECK-LABEL: @test17(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[X_LOAD:%.*]] = load ptr, ptr [[X:%.*]], align 8
; CHECK-NEXT: store i8 [[Y:%.*]], ptr [[X_LOAD]], align 1
; CHECK-NEXT: ret void
;
entry:
%x.load = load ptr, ptr %x
store i8 %y, ptr %x.load
ret void
}
; Check that we don't try change the type of the load by inserting a bitcast
; generating invalid IR.
%swift.error = type opaque
declare void @useSwiftError(ptr swifterror)
define void @test18(ptr swifterror %err) {
; CHECK-LABEL: @test18(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[SWIFTERROR:%.*]] = alloca swifterror ptr, align 8
; CHECK-NEXT: store ptr null, ptr [[SWIFTERROR]], align 8
; CHECK-NEXT: call void @useSwiftError(ptr nonnull swifterror [[SWIFTERROR]])
; CHECK-NEXT: [[ERR_RES:%.*]] = load ptr, ptr [[SWIFTERROR]], align 8
; CHECK-NEXT: store ptr [[ERR_RES]], ptr [[ERR:%.*]], align 8
; CHECK-NEXT: ret void
;
entry:
%swifterror = alloca swifterror ptr, align 8
store ptr null, ptr %swifterror, align 8
call void @useSwiftError(ptr nonnull swifterror %swifterror)
%err.res = load ptr, ptr %swifterror, align 8
store ptr %err.res, ptr %err, align 8
ret void
}
; Make sure we preseve the type of the store to a swifterror pointer.
declare void @initi8(ptr)
define void @test19(ptr swifterror %err) {
; CHECK-LABEL: @test19(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP:%.*]] = alloca ptr, align 8
; CHECK-NEXT: call void @initi8(ptr nonnull [[TMP]])
; CHECK-NEXT: [[ERR_RES:%.*]] = load ptr, ptr [[TMP]], align 8
; CHECK-NEXT: store ptr [[ERR_RES]], ptr [[ERR:%.*]], align 8
; CHECK-NEXT: ret void
;
entry:
%tmp = alloca ptr, align 8
call void @initi8(ptr %tmp)
%err.res = load ptr, ptr %tmp, align 8
store ptr %err.res, ptr %err, align 8
ret void
}
; Make sure we don't canonicalize accesses to scalable vectors.
define void @test20(ptr %x, ptr %y) {
; CHECK-LABEL: @test20(
; CHECK-NEXT: [[X_LOAD:%.*]] = load <vscale x 4 x i8>, ptr [[X:%.*]], align 1
; CHECK-NEXT: store <vscale x 4 x i8> [[X_LOAD]], ptr [[Y:%.*]], align 1
; CHECK-NEXT: ret void
;
%x.load = load <vscale x 4 x i8>, ptr %x, align 1
store <vscale x 4 x i8> %x.load, ptr %y, align 1
ret void
}
; Check that non-integral pointers are not coverted using inttoptr
declare void @use(ptr)
declare void @use.p1(ptr addrspace(1))
define i64 @test21(ptr %P) {
; CHECK-LABEL: @test21(
; CHECK-NEXT: [[X:%.*]] = load i64, ptr [[P:%.*]], align 8
; CHECK-NEXT: [[Y_CAST:%.*]] = inttoptr i64 [[X]] to ptr
; CHECK-NEXT: call void @use(ptr [[Y_CAST]])
; CHECK-NEXT: ret i64 [[X]]
;
%X = load i64, ptr %P
%Y = load ptr, ptr %P
call void @use(ptr %Y)
ret i64 %X
}
define i64 @test22(ptr %P) {
; CHECK-LABEL: @test22(
; CHECK-NEXT: [[X:%.*]] = load i64, ptr [[P:%.*]], align 8
; CHECK-NEXT: [[Y:%.*]] = load ptr addrspace(1), ptr [[P]], align 8
; CHECK-NEXT: call void @use.p1(ptr addrspace(1) [[Y]])
; CHECK-NEXT: ret i64 [[X]]
;
%X = load i64, ptr %P
%Y = load ptr addrspace(1), ptr %P
call void @use.p1(ptr addrspace(1) %Y)
ret i64 %X
}
declare void @use.v2.p0(<2 x ptr>)
declare void @use.v2.p1(<2 x ptr addrspace(1)>)
define <2 x i64> @test23(ptr %P) {
; CHECK-LABEL: @test23(
; CHECK-NEXT: [[X:%.*]] = load <2 x i64>, ptr [[P:%.*]], align 16
; CHECK-NEXT: [[Y:%.*]] = load <2 x ptr>, ptr [[P]], align 16
; CHECK-NEXT: call void @use.v2.p0(<2 x ptr> [[Y]])
; CHECK-NEXT: ret <2 x i64> [[X]]
;
%X = load <2 x i64>, ptr %P
%Y = load <2 x ptr>, ptr %P
call void @use.v2.p0(<2 x ptr> %Y)
ret <2 x i64> %X
}
define <2 x i64> @test24(ptr %P) {
; CHECK-LABEL: @test24(
; CHECK-NEXT: [[X:%.*]] = load <2 x i64>, ptr [[P:%.*]], align 16
; CHECK-NEXT: [[Y:%.*]] = load <2 x ptr addrspace(1)>, ptr [[P]], align 16
; CHECK-NEXT: call void @use.v2.p1(<2 x ptr addrspace(1)> [[Y]])
; CHECK-NEXT: ret <2 x i64> [[X]]
;
%X = load <2 x i64>, ptr %P
%Y = load <2 x ptr addrspace(1)>, ptr %P
call void @use.v2.p1(<2 x ptr addrspace(1)> %Y)
ret <2 x i64> %X
}
define i16 @load_from_zero_with_dynamic_offset(i64 %idx) {
; CHECK-LABEL: @load_from_zero_with_dynamic_offset(
; CHECK-NEXT: ret i16 0
;
%gep = getelementptr i16, ptr @GLOBAL, i64 %idx
%v = load i16, ptr %gep
ret i16 %v
}
declare ptr @llvm.strip.invariant.group.p0(ptr %p)
define i32 @load_via_strip_invariant_group() {
; CHECK-LABEL: @load_via_strip_invariant_group(
; CHECK-NEXT: ret i32 37
;
%a = call ptr @llvm.strip.invariant.group.p0(ptr @Y)
%b = getelementptr i8, ptr %a, i64 8
%d = load i32, ptr %b
ret i32 %d
}
; TODO: For non-byte-sized vectors, current implementation assumes there is
; padding to the next byte boundary between elements.
@foo = constant <2 x i4> <i4 u0x1, i4 u0x2>, align 8
define i4 @test_vector_load_i4_non_byte_sized() {
; CHECK-LABEL: @test_vector_load_i4_non_byte_sized(
; CHECK-NEXT: [[RES0:%.*]] = load i4, ptr @foo, align 1
; CHECK-NEXT: ret i4 [[RES0]]
;
%ptr0 = getelementptr i8, ptr @foo, i64 0
%res0 = load i4, ptr %ptr0, align 1
ret i4 %res0
}
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