4e2b4f97a0
Allow shrink-wrapping past memory accesses that only access globals or function arguments. This patch uses getUnderlyingObject to try to identify the accessed object by a given memory operand. If it is a global or an argument, it does not access the stack of the current function and should not block shrink wrapping. Note that the caller's stack may get accessed when passing an argument via the stack, but not the stack of the current function. This addresses part of the TODO from D63152. Reviewed By: thegameg Differential Revision: https://reviews.llvm.org/D149668
54 lines
1.4 KiB
LLVM
54 lines
1.4 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
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; RUN: llc -o - %s -mtriple=x86_64-- | FileCheck %s
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; Example of a decref operation with "immortal" objects.
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; void decref(long* refcount) {
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; long count = *refcount;
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; if (count == 1) { free_object() }
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; else if (count > 1) { *refcount = count - 1; }
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; else { /* immortal */ }
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; }
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; Resulting assembly should share flags from single CMP instruction for both
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; conditions!
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define void @decref(ptr %p) {
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; CHECK-LABEL: decref:
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; CHECK: # %bb.0:
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; CHECK-NEXT: movl (%rdi), %eax
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; CHECK-NEXT: cmpl $1, %eax
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; CHECK-NEXT: jne .LBB0_2
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; CHECK-NEXT: # %bb.1: # %bb_free
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; CHECK-NEXT: pushq %rax
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; CHECK-NEXT: .cfi_def_cfa_offset 16
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; CHECK-NEXT: callq free_object@PLT
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; CHECK-NEXT: addq $8, %rsp
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; CHECK-NEXT: .cfi_def_cfa_offset 8
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; CHECK-NEXT: .LBB0_4: # %end
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; CHECK-NEXT: retq
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; CHECK-NEXT: .LBB0_2: # %bb2
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; CHECK-NEXT: jle .LBB0_4
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; CHECK-NEXT: # %bb.3: # %bb_dec
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; CHECK-NEXT: decl %eax
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; CHECK-NEXT: movl %eax, (%rdi)
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; CHECK-NEXT: retq
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%count = load i32, ptr %p, align 4
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%cmp0 = icmp eq i32 %count, 1
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br i1 %cmp0, label %bb_free, label %bb2
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bb2:
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%cmp1 = icmp sgt i32 %count, 1
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br i1 %cmp1, label %bb_dec, label %end
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bb_dec:
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%dec = add nsw i32 %count, -1
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store i32 %dec, ptr %p, align 4
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br label %end
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bb_free:
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call void @free_object()
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br label %end
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end:
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ret void
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}
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declare void @free_object()
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