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4f4bd24ec4
The motivation for this patch starts with the epic fail example in PR18007: https://llvm.org/bugs/show_bug.cgi?id=18007 ...unfortunately, this patch makes no difference for that case, but it solves some simpler cases. We'll get there some day. :) The current 'or' matching code was using computeKnownBits() via isBaseWithConstantOffset() -> MaskedValueIsZero(), but that's an unnecessarily limited use. We can do more by copying the logic in ValueTracking's haveNoCommonBitsSet(), so we can treat the 'or' as if it was an 'add'. There's a TODO comment here because we should lift the bit-checking logic into a helper function, so it's not duplicated in DAGCombiner. An example of the better LEA matching: leal (%rdi,%rdi), %eax andl $1, %esi orl %esi, %eax Becomes: andl $1, %esi leal (%rsi,%rdi,2), %eax Differential Revision: http://reviews.llvm.org/D13956 llvm-svn: 252515
120 lines
2.7 KiB
LLVM
120 lines
2.7 KiB
LLVM
; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s
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; InstCombine and DAGCombiner transform an 'add' into an 'or'
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; if there are no common bits from the incoming operands.
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; LEA instruction selection should be able to see through that
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; transform and reduce add/shift/or instruction counts.
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define i32 @or_shift1_and1(i32 %x, i32 %y) {
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; CHECK-LABEL: or_shift1_and1:
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; CHECK: # BB#0:
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; CHECK-NEXT: andl $1, %esi
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; CHECK-NEXT: leal (%rsi,%rdi,2), %eax
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; CHECK-NEXT: retq
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%shl = shl i32 %x, 1
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%and = and i32 %y, 1
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%or = or i32 %and, %shl
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ret i32 %or
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}
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define i32 @or_shift1_and1_swapped(i32 %x, i32 %y) {
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; CHECK-LABEL: or_shift1_and1_swapped:
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; CHECK: # BB#0:
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; CHECK-NEXT: andl $1, %esi
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; CHECK-NEXT: leal (%rsi,%rdi,2), %eax
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; CHECK-NEXT: retq
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%shl = shl i32 %x, 1
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%and = and i32 %y, 1
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%or = or i32 %shl, %and
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ret i32 %or
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}
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define i32 @or_shift2_and1(i32 %x, i32 %y) {
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; CHECK-LABEL: or_shift2_and1:
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; CHECK: # BB#0:
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; CHECK-NEXT: andl $1, %esi
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; CHECK-NEXT: leal (%rsi,%rdi,4), %eax
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; CHECK-NEXT: retq
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%shl = shl i32 %x, 2
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%and = and i32 %y, 1
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%or = or i32 %shl, %and
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ret i32 %or
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}
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define i32 @or_shift3_and1(i32 %x, i32 %y) {
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; CHECK-LABEL: or_shift3_and1:
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; CHECK: # BB#0:
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; CHECK-NEXT: andl $1, %esi
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; CHECK-NEXT: leal (%rsi,%rdi,8), %eax
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; CHECK-NEXT: retq
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%shl = shl i32 %x, 3
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%and = and i32 %y, 1
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%or = or i32 %shl, %and
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ret i32 %or
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}
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define i32 @or_shift3_and7(i32 %x, i32 %y) {
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; CHECK-LABEL: or_shift3_and7:
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; CHECK: # BB#0:
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; CHECK-NEXT: andl $7, %esi
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; CHECK-NEXT: leal (%rsi,%rdi,8), %eax
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; CHECK-NEXT: retq
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%shl = shl i32 %x, 3
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%and = and i32 %y, 7
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%or = or i32 %shl, %and
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ret i32 %or
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}
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; The shift is too big for an LEA.
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define i32 @or_shift4_and1(i32 %x, i32 %y) {
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; CHECK-LABEL: or_shift4_and1:
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; CHECK: # BB#0:
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; CHECK-NEXT: shll $4, %edi
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; CHECK-NEXT: andl $1, %esi
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; CHECK-NEXT: leal (%rsi,%rdi), %eax
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; CHECK-NEXT: retq
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%shl = shl i32 %x, 4
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%and = and i32 %y, 1
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%or = or i32 %shl, %and
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ret i32 %or
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}
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; The mask is too big for the shift, so the 'or' isn't equivalent to an 'add'.
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define i32 @or_shift3_and8(i32 %x, i32 %y) {
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; CHECK-LABEL: or_shift3_and8:
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; CHECK: # BB#0:
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; CHECK-NEXT: leal (,%rdi,8), %eax
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; CHECK-NEXT: andl $8, %esi
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; CHECK-NEXT: orl %esi, %eax
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; CHECK-NEXT: retq
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%shl = shl i32 %x, 3
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%and = and i32 %y, 8
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%or = or i32 %shl, %and
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ret i32 %or
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}
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; 64-bit operands should work too.
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define i64 @or_shift1_and1_64(i64 %x, i64 %y) {
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; CHECK-LABEL: or_shift1_and1_64:
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; CHECK: # BB#0:
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; CHECK-NEXT: andl $1, %esi
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; CHECK-NEXT: leaq (%rsi,%rdi,2), %rax
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; CHECK-NEXT: retq
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%shl = shl i64 %x, 1
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%and = and i64 %y, 1
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%or = or i64 %and, %shl
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ret i64 %or
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}
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