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llvm-mirror/test/CodeGen/X86/align-down.ll
Roman Lebedev 24c9de9750 [DAGCombiner][X86][AArch64] Generalize A-(A&B)->A&(~B) fold (PR44448) 
The fold 'A - (A & (B - 1))' -> 'A & (0 - B)'
added in 8dab0a4a7d691f2704f1079538e0ef29548db159
is too specific. It should/can just be 'A - (A & B)' -> 'A & (~B)'

Even if we don't manage to fold `~` into B,
we have likely formed `ANDN` node.
Also, this way there's less similar-but-duplicate folds.

Name: X - (X & Y)  ->  X & (~Y)
%o = and i32 %X, %Y
%r = sub i32 %X, %o
  =>
%n = xor i32 %Y, -1
%r = and i32 %X, %n

https://rise4fun.com/Alive/kOUl

See
  https://bugs.llvm.org/show_bug.cgi?id=44448
  https://reviews.llvm.org/D71499
2020-01-03 17:55:47 +03:00

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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -mtriple=i686-unknown-linux-gnu < %s | FileCheck %s --check-prefixes=CHECK,NOBMI,X86,NOBMI-X86
; RUN: llc -mtriple=i686-unknown-linux-gnu -mattr=+bmi < %s | FileCheck %s --check-prefixes=CHECK,BMI,X86,BMI-X86
; RUN: llc -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s --check-prefixes=CHECK,NOBMI,X64,NOBMI-X64
; RUN: llc -mtriple=x86_64-unknown-linux-gnu -mattr=+bmi < %s | FileCheck %s --check-prefixes=CHECK,BMI,X64,BMI-X64
; Fold
; ptr - (ptr & (alignment-1))
; To
; ptr & (0 - alignment)
;
; This needs to be a backend-level fold because only by now pointers
; are just registers; in middle-end IR this can only be done via @llvm.ptrmask()
; intrinsic which is not sufficiently widely-spread yet.
;
; https://bugs.llvm.org/show_bug.cgi?id=44448
; The basic positive tests
define i32 @t0_32(i32 %ptr, i32 %alignment) nounwind {
; X86-LABEL: t0_32:
; X86: # %bb.0:
; X86-NEXT: xorl %eax, %eax
; X86-NEXT: subl {{[0-9]+}}(%esp), %eax
; X86-NEXT: andl {{[0-9]+}}(%esp), %eax
; X86-NEXT: retl
;
; X64-LABEL: t0_32:
; X64: # %bb.0:
; X64-NEXT: movl %esi, %eax
; X64-NEXT: negl %eax
; X64-NEXT: andl %edi, %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
%bias = and i32 %ptr, %mask
%r = sub i32 %ptr, %bias
ret i32 %r
}
define i64 @t1_64(i64 %ptr, i64 %alignment) nounwind {
; X86-LABEL: t1_64:
; X86: # %bb.0:
; X86-NEXT: xorl %edx, %edx
; X86-NEXT: xorl %eax, %eax
; X86-NEXT: subl {{[0-9]+}}(%esp), %eax
; X86-NEXT: sbbl {{[0-9]+}}(%esp), %edx
; X86-NEXT: andl {{[0-9]+}}(%esp), %edx
; X86-NEXT: andl {{[0-9]+}}(%esp), %eax
; X86-NEXT: retl
;
; X64-LABEL: t1_64:
; X64: # %bb.0:
; X64-NEXT: movq %rsi, %rax
; X64-NEXT: negq %rax
; X64-NEXT: andq %rdi, %rax
; X64-NEXT: retq
%mask = add i64 %alignment, -1
%bias = and i64 %ptr, %mask
%r = sub i64 %ptr, %bias
ret i64 %r
}
define i32 @t2_commutative(i32 %ptr, i32 %alignment) nounwind {
; X86-LABEL: t2_commutative:
; X86: # %bb.0:
; X86-NEXT: xorl %eax, %eax
; X86-NEXT: subl {{[0-9]+}}(%esp), %eax
; X86-NEXT: andl {{[0-9]+}}(%esp), %eax
; X86-NEXT: retl
;
; X64-LABEL: t2_commutative:
; X64: # %bb.0:
; X64-NEXT: movl %esi, %eax
; X64-NEXT: negl %eax
; X64-NEXT: andl %edi, %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
%bias = and i32 %mask, %ptr ; swapped
%r = sub i32 %ptr, %bias
ret i32 %r
}
; Extra use tests
define i32 @t3_extrause0(i32 %ptr, i32 %alignment, i32* %mask_storage) nounwind {
; X86-LABEL: t3_extrause0:
; X86: # %bb.0:
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: leal -1(%eax), %edx
; X86-NEXT: movl %edx, (%ecx)
; X86-NEXT: negl %eax
; X86-NEXT: andl {{[0-9]+}}(%esp), %eax
; X86-NEXT: retl
;
; X64-LABEL: t3_extrause0:
; X64: # %bb.0:
; X64-NEXT: movl %esi, %eax
; X64-NEXT: leal -1(%rax), %ecx
; X64-NEXT: movl %ecx, (%rdx)
; X64-NEXT: negl %eax
; X64-NEXT: andl %edi, %eax
; X64-NEXT: # kill: def $eax killed $eax killed $rax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
store i32 %mask, i32* %mask_storage
%bias = and i32 %ptr, %mask
%r = sub i32 %ptr, %bias
ret i32 %r
}
define i32 @n4_extrause1(i32 %ptr, i32 %alignment, i32* %bias_storage) nounwind {
; X86-LABEL: n4_extrause1:
; X86: # %bb.0:
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %edx
; X86-NEXT: decl %edx
; X86-NEXT: andl %eax, %edx
; X86-NEXT: movl %edx, (%ecx)
; X86-NEXT: subl %edx, %eax
; X86-NEXT: retl
;
; X64-LABEL: n4_extrause1:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: decl %esi
; X64-NEXT: andl %edi, %esi
; X64-NEXT: movl %esi, (%rdx)
; X64-NEXT: subl %esi, %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
%bias = and i32 %ptr, %mask ; has extra uses, can't fold
store i32 %bias, i32* %bias_storage
%r = sub i32 %ptr, %bias
ret i32 %r
}
define i32 @n5_extrause2(i32 %ptr, i32 %alignment, i32* %mask_storage, i32* %bias_storage) nounwind {
; X86-LABEL: n5_extrause2:
; X86: # %bb.0:
; X86-NEXT: pushl %esi
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %edx
; X86-NEXT: movl {{[0-9]+}}(%esp), %esi
; X86-NEXT: decl %esi
; X86-NEXT: movl %esi, (%edx)
; X86-NEXT: andl %eax, %esi
; X86-NEXT: movl %esi, (%ecx)
; X86-NEXT: subl %esi, %eax
; X86-NEXT: popl %esi
; X86-NEXT: retl
;
; X64-LABEL: n5_extrause2:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: decl %esi
; X64-NEXT: movl %esi, (%rdx)
; X64-NEXT: andl %edi, %esi
; X64-NEXT: movl %esi, (%rcx)
; X64-NEXT: subl %esi, %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
store i32 %mask, i32* %mask_storage
%bias = and i32 %ptr, %mask ; has extra uses, can't fold
store i32 %bias, i32* %bias_storage
%r = sub i32 %ptr, %bias
ret i32 %r
}
; Negative tests
define i32 @n6_different_ptrs(i32 %ptr0, i32 %ptr1, i32 %alignment) nounwind {
; X86-LABEL: n6_different_ptrs:
; X86: # %bb.0:
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: decl %ecx
; X86-NEXT: andl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: subl %ecx, %eax
; X86-NEXT: retl
;
; X64-LABEL: n6_different_ptrs:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: decl %edx
; X64-NEXT: andl %esi, %edx
; X64-NEXT: subl %edx, %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
%bias = and i32 %ptr1, %mask ; not %ptr0
%r = sub i32 %ptr0, %bias ; not %ptr1
ret i32 %r
}
define i32 @n7_different_ptrs_commutative(i32 %ptr0, i32 %ptr1, i32 %alignment) nounwind {
; X86-LABEL: n7_different_ptrs_commutative:
; X86: # %bb.0:
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: decl %ecx
; X86-NEXT: andl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: subl %ecx, %eax
; X86-NEXT: retl
;
; X64-LABEL: n7_different_ptrs_commutative:
; X64: # %bb.0:
; X64-NEXT: movl %edi, %eax
; X64-NEXT: decl %edx
; X64-NEXT: andl %esi, %edx
; X64-NEXT: subl %edx, %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
%bias = and i32 %mask, %ptr1 ; swapped, not %ptr0
%r = sub i32 %ptr0, %bias ; not %ptr1
ret i32 %r
}
define i32 @n8_not_lowbit_mask(i32 %ptr, i32 %alignment) nounwind {
; NOBMI-X86-LABEL: n8_not_lowbit_mask:
; NOBMI-X86: # %bb.0:
; NOBMI-X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; NOBMI-X86-NEXT: incl %eax
; NOBMI-X86-NEXT: notl %eax
; NOBMI-X86-NEXT: andl {{[0-9]+}}(%esp), %eax
; NOBMI-X86-NEXT: retl
;
; BMI-X86-LABEL: n8_not_lowbit_mask:
; BMI-X86: # %bb.0:
; BMI-X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; BMI-X86-NEXT: incl %eax
; BMI-X86-NEXT: andnl {{[0-9]+}}(%esp), %eax, %eax
; BMI-X86-NEXT: retl
;
; NOBMI-X64-LABEL: n8_not_lowbit_mask:
; NOBMI-X64: # %bb.0:
; NOBMI-X64-NEXT: movl %esi, %eax
; NOBMI-X64-NEXT: incl %eax
; NOBMI-X64-NEXT: notl %eax
; NOBMI-X64-NEXT: andl %edi, %eax
; NOBMI-X64-NEXT: retq
;
; BMI-X64-LABEL: n8_not_lowbit_mask:
; BMI-X64: # %bb.0:
; BMI-X64-NEXT: incl %esi
; BMI-X64-NEXT: andnl %edi, %esi, %eax
; BMI-X64-NEXT: retq
%mask = add i32 %alignment, 1 ; not -1
%bias = and i32 %ptr, %mask
%r = sub i32 %ptr, %bias
ret i32 %r
}
define i32 @n9_sub_is_not_commutative(i32 %ptr, i32 %alignment) nounwind {
; X86-LABEL: n9_sub_is_not_commutative:
; X86: # %bb.0:
; X86-NEXT: movl {{[0-9]+}}(%esp), %ecx
; X86-NEXT: movl {{[0-9]+}}(%esp), %eax
; X86-NEXT: decl %eax
; X86-NEXT: andl %ecx, %eax
; X86-NEXT: subl %ecx, %eax
; X86-NEXT: retl
;
; X64-LABEL: n9_sub_is_not_commutative:
; X64: # %bb.0:
; X64-NEXT: movl %esi, %eax
; X64-NEXT: decl %eax
; X64-NEXT: andl %edi, %eax
; X64-NEXT: subl %edi, %eax
; X64-NEXT: retq
%mask = add i32 %alignment, -1
%bias = and i32 %ptr, %mask
%r = sub i32 %bias, %ptr ; wrong order
ret i32 %r
}
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