1; RUN: opt -passes=bpf-preserve-static-offset -mtriple=bpf-pc-linux -S -o - %s | FileCheck %s 2; 3; Check that bpf-preserve-static-offset folds chain of GEP instructions. 4; The GEP chain in this example has unexpected shape and thus is 5; folded as i8 access. 6; 7; Source (IR modified by hand): 8; #define __ctx __attribute__((preserve_static_offset)) 9; 10; struct foo { 11; char a[2]; 12; }; 13; 14; struct bar { 15; char a; 16; struct foo b; 17; } __ctx; 18; 19; extern void consume(char); 20; 21; void buz(struct bar *p) { 22; consume((&p->b)[1].a[1]); 23; } 24; 25; Compilation flag: 26; clang -cc1 -O2 -triple bpf -S -emit-llvm -disable-llvm-passes -o - \ 27; | opt -passes=function(sroa) -S -o - 28; 29; Modified to remove 'inbounds' from one of the GEP instructions. 30 31%struct.bar = type { i8, %struct.foo } 32%struct.foo = type { [2 x i8] } 33 34; Function Attrs: nounwind 35define dso_local void @buz(ptr noundef %p) #0 { 36entry: 37 %0 = call ptr @llvm.preserve.static.offset(ptr %p) 38 %b = getelementptr inbounds %struct.bar, ptr %0, i32 0, i32 1 39 %arrayidx = getelementptr inbounds %struct.foo, ptr %b, i64 1 40; ^^^^^ 41; folded as i8 access because of this index 42 %a = getelementptr %struct.foo, ptr %arrayidx, i32 0, i32 0 43 %arrayidx1 = getelementptr inbounds [2 x i8], ptr %a, i64 0, i64 1 44 %1 = load i8, ptr %arrayidx1, align 1, !tbaa !2 45 call void @consume(i8 noundef signext %1) 46 ret void 47} 48 49; CHECK: %[[v1:.*]] = call i8 (ptr, i1, i8, i8, i8, i1, ...) 50; CHECK-SAME: @llvm.bpf.getelementptr.and.load.i8 51; CHECK-SAME: (ptr readonly elementtype(i8) %{{[^,]+}}, 52; CHECK-SAME: i1 false, i8 0, i8 1, i8 0, i1 false, i64 immarg 4) 53; ^^^^^^^^ ^^^^^^^^^^^^ 54; not inbounds ---' | 55; offset from 'struct bar' start -------------' 56; CHECK-NEXT: call void @consume(i8 noundef signext %[[v1]]) 57 58declare void @consume(i8 noundef signext) #1 59 60; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none) 61declare ptr @llvm.preserve.static.offset(ptr readnone) #2 62 63attributes #0 = { nounwind "no-trapping-math"="true" "stack-protector-buffer-size"="8" } 64attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" } 65attributes #2 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) } 66 67!llvm.module.flags = !{!0} 68!llvm.ident = !{!1} 69 70!0 = !{i32 1, !"wchar_size", i32 4} 71!1 = !{!"clang"} 72!2 = !{!3, !3, i64 0} 73!3 = !{!"omnipotent char", !4, i64 0} 74!4 = !{!"Simple C/C++ TBAA"} 75