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[InstCombine] add tests to document bitcast + bitwise-logic behavior; NFC

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The solution for PR26702 ( https://bugs.llvm.org/show_bug.cgi?id=26702 )
added a canonicalization rule, but the minimal regression tests don't 
demonstrate how that rule interacts with other folds.

llvm-svn: 303750
This commit is contained in:
Sanjay Patel 2017-05-24 14:21:31 +00:00
parent da6888ed6b
commit 733d481cb3
1 changed files with 45 additions and 0 deletions
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45
test/Transforms/InstCombine/bitcast.ll
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@ -70,6 +70,51 @@ define <2 x i32> @or_bitcast_int_to_vec(i64 %a) {
ret <2 x i32> %t2
}
; PR26702 - https://bugs.llvm.org//show_bug.cgi?id=26702
; Bitcast is canonicalized below logic, so we can see the not-not pattern.
define <2 x i64> @is_negative(<4 x i32> %x) {
; CHECK-LABEL: @is_negative(
; CHECK-NEXT: [[LOBIT:%.*]] = ashr <4 x i32> %x, <i32 31, i32 31, i32 31, i32 31>
; CHECK-NEXT: [[NOTNOT:%.*]] = bitcast <4 x i32> [[LOBIT]] to <2 x i64>
; CHECK-NEXT: ret <2 x i64> [[NOTNOT]]
;
%lobit = ashr <4 x i32> %x, <i32 31, i32 31, i32 31, i32 31>
%not = xor <4 x i32> %lobit, <i32 -1, i32 -1, i32 -1, i32 -1>
%bc = bitcast <4 x i32> %not to <2 x i64>
%notnot = xor <2 x i64> %bc, <i64 -1, i64 -1>
ret <2 x i64> %notnot
}
; This variation has an extra bitcast at the end. This means that the 2nd xor
; can be done in <4 x i32> to eliminate a bitcast regardless of canonicalizaion.
define <4 x i32> @is_negative_bonus_bitcast(<4 x i32> %x) {
; CHECK-LABEL: @is_negative_bonus_bitcast(
; CHECK-NEXT: [[LOBIT:%.*]] = ashr <4 x i32> %x, <i32 31, i32 31, i32 31, i32 31>
; CHECK-NEXT: ret <4 x i32> [[LOBIT]]
;
%lobit = ashr <4 x i32> %x, <i32 31, i32 31, i32 31, i32 31>
%not = xor <4 x i32> %lobit, <i32 -1, i32 -1, i32 -1, i32 -1>
%bc = bitcast <4 x i32> %not to <2 x i64>
%notnot = xor <2 x i64> %bc, <i64 -1, i64 -1>
%bc2 = bitcast <2 x i64> %notnot to <4 x i32>
ret <4 x i32> %bc2
}
; Negative test: bitcasts are canonicalized below bitwise logic. No changes here.
define <2 x i8> @canonicalize_bitcast_logic_with_constant(<4 x i4> %x) {
; CHECK-LABEL: @canonicalize_bitcast_logic_with_constant(
; CHECK-NEXT: [[A:%.*]] = and <4 x i4> %x, <i4 0, i4 -8, i4 0, i4 -8>
; CHECK-NEXT: [[B:%.*]] = bitcast <4 x i4> [[A]] to <2 x i8>
; CHECK-NEXT: ret <2 x i8> [[B]]
;
%a = and <4 x i4> %x, <i4 0, i4 8, i4 0, i4 8>
%b = bitcast <4 x i4> %a to <2 x i8>
ret <2 x i8> %b
}
; PR27925 - https://llvm.org/bugs/show_bug.cgi?id=27925
define <4 x i32> @bitcasts_and_bitcast(<4 x i32> %a, <8 x i16> %b) {