high-pressure-on-ptrregs.ll
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; RUN: llc < %s -march=avr | FileCheck %s
; This tests how LLVM handles IR which puts very high
; presure on the PTRREGS class for the register allocator.
;
; This causes a problem because we only have one small register
; class for loading and storing from pointers - 'PTRREGS'.
; One of these registers is also used for the frame pointer, meaning
; that we only ever have two registers available for these operations.
;
; There is an existing bug filed for this issue - PR14879.
;
; The specific failure:
; LLVM ERROR: ran out of registers during register allocation
;
; It has been assembled from the following c code:
;
; struct ss
; {
; int a;
; int b;
; int c;
; };
;
; void loop(struct ss *x, struct ss **y, int z)
; {
; int i;
; for (i=0; i<z; ++i)
; {
; x->c += y[i]->b;
; }
; }
%struct.ss = type { i16, i16, i16 }
; CHECK-LABEL: loop
define void @loop(%struct.ss* %x, %struct.ss** %y, i16 %z) #0 {
entry:
%x.addr = alloca %struct.ss*, align 2
%y.addr = alloca %struct.ss**, align 2
%z.addr = alloca i16, align 2
%i = alloca i16, align 2
store %struct.ss* %x, %struct.ss** %x.addr, align 2
store %struct.ss** %y, %struct.ss*** %y.addr, align 2
store i16 %z, i16* %z.addr, align 2
store i16 0, i16* %i, align 2
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%tmp = load i16, i16* %i, align 2
%tmp1 = load i16, i16* %z.addr, align 2
%cmp = icmp slt i16 %tmp, %tmp1
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%tmp2 = load %struct.ss**, %struct.ss*** %y.addr, align 2
%tmp3 = load i16, i16* %i, align 2
%arrayidx = getelementptr inbounds %struct.ss*, %struct.ss** %tmp2, i16 %tmp3
%tmp4 = load %struct.ss*, %struct.ss** %arrayidx, align 2
%b = getelementptr inbounds %struct.ss, %struct.ss* %tmp4, i32 0, i32 1
%tmp5 = load i16, i16* %b, align 2
%tmp6 = load %struct.ss*, %struct.ss** %x.addr, align 2
%c = getelementptr inbounds %struct.ss, %struct.ss* %tmp6, i32 0, i32 2
%tmp7 = load i16, i16* %c, align 2
%add = add nsw i16 %tmp7, %tmp5
store i16 %add, i16* %c, align 2
br label %for.inc
for.inc: ; preds = %for.body
%tmp8 = load i16, i16* %i, align 2
%inc = add nsw i16 %tmp8, 1
store i16 %inc, i16* %i, align 2
br label %for.cond
for.end: ; preds = %for.cond
ret void
}