[ConstantFold] Remove unnecessary bounded index restriction

The fold for merging a GEP of GEP into a single GEP currently bails
if doing so would result in notional overindexing. The justification
given in the comment above this check is dangerously incorrect: GEPs
with notional overindexing are perfectly fine, and if some code
treats them incorrectly, then that code is broken, not the GEP.
Such a GEP might legally appear in source IR, so only preventing
its creation cannot be sufficient. (The constant folder also ends
up canonicalizing the GEP to remove the notional overindexing, but
that's neither here nor there.)

This check dates back to
llvm/llvm-project@bd4fef4,
and as far as I can tell the original issue this was trying to
patch around has since been resolved.

Differential Revision: https://reviews.llvm.org/D116587

Author: nikic

clang/test/CodeGen/clear_cache.c

@@ -10,7 +10,7 @@ char buffer[32] = "This is a largely unused buffer";
 // CHECK-NEXT:  entry:
 // CHECK-NEXT:    [[RETVAL:%.*]] = alloca i32, align 4
 // CHECK-NEXT:    store i32 0, i32* [[RETVAL]], align 4
-// CHECK-NEXT:    call void @llvm.clear_cache(i8* getelementptr inbounds ([32 x i8], [32 x i8]* @buffer, i64 0, i64 0), i8* getelementptr inbounds (i8, i8* getelementptr inbounds ([32 x i8], [32 x i8]* @buffer, i64 0, i64 0), i64 32))
+// CHECK-NEXT:    call void @llvm.clear_cache(i8* getelementptr inbounds ([32 x i8], [32 x i8]* @buffer, i64 0, i64 0), i8* getelementptr inbounds ([32 x i8], [32 x i8]* @buffer, i64 1, i64 0))
 // CHECK-NEXT:    ret i32 0
 //
 int main() {

clang/test/CodeGenCXX/cxx11-initializer-aggregate.cpp

@@ -77,7 +77,7 @@ int &fn2(int &v) {
 // CHECK: br i1
 //
 // CHECK: getelementptr inbounds {{.*}}, i64 1
-// CHECK: icmp eq {{.*}}, i64 30
+// CHECK: icmp eq {{.*}}, getelementptr inbounds {{.*}}, i64 1, i64 0
 // CHECK: br i1
 //
 // CHECK: call i32 @__cxa_atexit(

clang/test/CodeGenCXX/for-range.cpp

@@ -43,7 +43,7 @@ extern B array[5];
 // CHECK-NEXT:    call void @_ZN1AC1Ev(%struct.A* nonnull align 1 dereferenceable(1) [[A]])
 // CHECK-NEXT:    store [5 x %struct.B]* @array, [5 x %struct.B]** [[__RANGE1]], align 8
 // CHECK-NEXT:    store %struct.B* getelementptr inbounds ([5 x %struct.B], [5 x %struct.B]* @array, i64 0, i64 0), %struct.B** [[__BEGIN1]], align 8
-// CHECK-NEXT:    store %struct.B* getelementptr inbounds ([[STRUCT_B]], %struct.B* getelementptr inbounds ([5 x %struct.B], [5 x %struct.B]* @array, i64 0, i64 0), i64 5), %struct.B** [[__END1]], align 8
+// CHECK-NEXT:    store %struct.B* getelementptr inbounds ([5 x %struct.B], [5 x %struct.B]* @array, i64 1, i64 0), %struct.B** [[__END1]], align 8
 // CHECK-NEXT:    br label [[FOR_COND:%.*]]
 // CHECK:       for.cond:
 // CHECK-NEXT:    [[TMP0:%.*]] = load %struct.B*, %struct.B** [[__BEGIN1]], align 8

clang/test/CodeGenCXX/global-array-destruction.cpp

@@ -39,15 +39,15 @@ struct T {
 T t[2][3] = { 1.0, 2, 3.0, 4, 5.0, 6, 7.0, 8, 9.0, 10, 11.0, 12 };
 
 // CHECK: call {{.*}} @__cxa_atexit
-// CHECK: getelementptr inbounds ({{.*}} getelementptr inbounds ([2 x [3 x {{.*}}]], [2 x [3 x {{.*}}]]* @t, i32 0, i32 0, i32 0), i64 6)
+// CHECK: getelementptr inbounds ([2 x [3 x {{.*}}]], [2 x [3 x {{.*}}]]* @t, i64 1, i64 0, i64 0)
 // CHECK: call void @_ZN1TD1Ev
 // CHECK: icmp eq {{.*}} @t
 // CHECK: br i1 {{.*}}
 
 static T t2[2][3] = { 1.0, 2, 3.0, 4, 5.0, 6, 7.0, 8, 9.0, 10, 11.0, 12 };
 
 // CHECK: call {{.*}} @__cxa_atexit
-// CHECK: getelementptr inbounds ({{.*}} getelementptr inbounds ([2 x [3 x {{.*}}]], [2 x [3 x {{.*}}]]* @_ZL2t2, i32 0, i32 0, i32 0), i64 6)
+// CHECK: getelementptr inbounds ([2 x [3 x {{.*}}]], [2 x [3 x {{.*}}]]* @_ZL2t2, i64 1, i64 0, i64 0)
 // CHECK: call void @_ZN1TD1Ev
 // CHECK: icmp eq {{.*}} @_ZL2t2
 // CHECK: br i1 {{.*}}
@@ -56,7 +56,7 @@ using U = T[2][3];
 U &&u = U{ {{1.0, 2}, {3.0, 4}, {5.0, 6}}, {{7.0, 8}, {9.0, 10}, {11.0, 12}} };
 
 // CHECK: call {{.*}} @__cxa_atexit
-// CHECK: getelementptr inbounds ({{.*}}* getelementptr inbounds ([2 x [3 x {{.*}}]], [2 x [3 x {{.*}}]]* @_ZGR1u_, i32 0, i32 0, i32 0), i64 6)
+// CHECK: getelementptr inbounds ([2 x [3 x {{.*}}]], [2 x [3 x {{.*}}]]* @_ZGR1u_, i64 1, i64 0, i64 0)
 // CHECK: call void @_ZN1TD1Ev
 // CHECK: icmp eq {{.*}} @_ZGR1u_
 // CHECK: br i1 {{.*}}

clang/test/CodeGenCXX/template-param-objects.cpp

@@ -15,5 +15,5 @@ template<S s> constexpr const char *end() { return s.buf + __builtin_strlen(s.bu
 const char *p = begin<S{"hello world"}>();
 // ITANIUM: @q
 // MSABI: @"?q@@3PEBDEB"
-// CHECK-SAME: global i8* getelementptr (i8, i8* getelementptr inbounds ({{.*}}* [[HELLO]], i32 0, i32 0, i32 0, i32 0), i64 11)
+// CHECK-SAME: global i8* getelementptr ({{.*}}* [[HELLO]], i32 0, i32 0, i32 0, i64 11)
 const char *q = end<S{"hello world"}>();

clang/test/OpenMP/for_firstprivate_codegen.cpp

@@ -227,8 +227,8 @@ int main() {
 // CHECK1-NEXT:    store i8* [[TMP0]], i8** [[DOTADDR]], align 8
 // CHECK1-NEXT:    br label [[ARRAYDESTROY_BODY:%.*]]
 // CHECK1:       arraydestroy.body:
-// CHECK1-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([[STRUCT_S:%.*]], %struct.S* getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0), i64 2), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
-// CHECK1-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
+// CHECK1-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i64 1, i64 0), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
+// CHECK1-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S:%.*]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
 // CHECK1-NEXT:    call void @_ZN1SIfED1Ev(%struct.S* nonnull align 4 dereferenceable(4) [[ARRAYDESTROY_ELEMENT]]) #[[ATTR2]]
 // CHECK1-NEXT:    [[ARRAYDESTROY_DONE:%.*]] = icmp eq %struct.S* [[ARRAYDESTROY_ELEMENT]], getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0)
 // CHECK1-NEXT:    br i1 [[ARRAYDESTROY_DONE]], label [[ARRAYDESTROY_DONE1:%.*]], label [[ARRAYDESTROY_BODY]]
@@ -820,8 +820,8 @@ int main() {
 // CHECK2-NEXT:    store i8* [[TMP0]], i8** [[DOTADDR]], align 8
 // CHECK2-NEXT:    br label [[ARRAYDESTROY_BODY:%.*]]
 // CHECK2:       arraydestroy.body:
-// CHECK2-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([[STRUCT_S:%.*]], %struct.S* getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0), i64 2), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
-// CHECK2-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
+// CHECK2-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i64 1, i64 0), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
+// CHECK2-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S:%.*]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
 // CHECK2-NEXT:    call void @_ZN1SIfED1Ev(%struct.S* nonnull align 4 dereferenceable(4) [[ARRAYDESTROY_ELEMENT]]) #[[ATTR2]]
 // CHECK2-NEXT:    [[ARRAYDESTROY_DONE:%.*]] = icmp eq %struct.S* [[ARRAYDESTROY_ELEMENT]], getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0)
 // CHECK2-NEXT:    br i1 [[ARRAYDESTROY_DONE]], label [[ARRAYDESTROY_DONE1:%.*]], label [[ARRAYDESTROY_BODY]]
@@ -1413,8 +1413,8 @@ int main() {
 // CHECK3-NEXT:    store i8* [[TMP0]], i8** [[DOTADDR]], align 8
 // CHECK3-NEXT:    br label [[ARRAYDESTROY_BODY:%.*]]
 // CHECK3:       arraydestroy.body:
-// CHECK3-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([[STRUCT_S:%.*]], %struct.S* getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0), i64 2), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
-// CHECK3-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
+// CHECK3-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i64 1, i64 0), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
+// CHECK3-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S:%.*]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
 // CHECK3-NEXT:    call void @_ZN1SIfED1Ev(%struct.S* nonnull align 4 dereferenceable(4) [[ARRAYDESTROY_ELEMENT]]) #[[ATTR2]]
 // CHECK3-NEXT:    [[ARRAYDESTROY_DONE:%.*]] = icmp eq %struct.S* [[ARRAYDESTROY_ELEMENT]], getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0)
 // CHECK3-NEXT:    br i1 [[ARRAYDESTROY_DONE]], label [[ARRAYDESTROY_DONE1:%.*]], label [[ARRAYDESTROY_BODY]]
@@ -1638,8 +1638,8 @@ int main() {
 // CHECK4-NEXT:    store i8* [[TMP0]], i8** [[DOTADDR]], align 8
 // CHECK4-NEXT:    br label [[ARRAYDESTROY_BODY:%.*]]
 // CHECK4:       arraydestroy.body:
-// CHECK4-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([[STRUCT_S:%.*]], %struct.S* getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0), i64 2), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
-// CHECK4-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
+// CHECK4-NEXT:    [[ARRAYDESTROY_ELEMENTPAST:%.*]] = phi %struct.S* [ getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i64 1, i64 0), [[ENTRY:%.*]] ], [ [[ARRAYDESTROY_ELEMENT:%.*]], [[ARRAYDESTROY_BODY]] ]
+// CHECK4-NEXT:    [[ARRAYDESTROY_ELEMENT]] = getelementptr inbounds [[STRUCT_S:%.*]], %struct.S* [[ARRAYDESTROY_ELEMENTPAST]], i64 -1
 // CHECK4-NEXT:    call void @_ZN1SIfED1Ev(%struct.S* nonnull align 4 dereferenceable(4) [[ARRAYDESTROY_ELEMENT]]) #[[ATTR2]]
 // CHECK4-NEXT:    [[ARRAYDESTROY_DONE:%.*]] = icmp eq %struct.S* [[ARRAYDESTROY_ELEMENT]], getelementptr inbounds ([2 x %struct.S], [2 x %struct.S]* @s_arr, i32 0, i32 0)
 // CHECK4-NEXT:    br i1 [[ARRAYDESTROY_DONE]], label [[ARRAYDESTROY_DONE1:%.*]], label [[ARRAYDESTROY_BODY]]
@@ -1848,4 +1848,3 @@ int main() {
 // CHECK4-NEXT:    call void @__cxx_global_var_init.2()
 // CHECK4-NEXT:    ret void
 //
-//