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[InstCombine] add tests for abs using bit hackery; NFC

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llvm-svn: 320068
This commit is contained in:
Sanjay Patel 2017-12-07 18:13:33 +00:00
parent e2564051be
commit 6cfc136870
1 changed files with 103 additions and 21 deletions
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124
llvm/test/Transforms/InstCombine/abs-1.ll
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@ -1,5 +1,3 @@
; Test that the abs library call simplifier works correctly.
;
; RUN: opt < %s -instcombine -S | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
@ -8,34 +6,118 @@ declare i32 @abs(i32)
declare i64 @labs(i64)
declare i64 @llabs(i64)
; Check abs(x) -> x >s -1 ? x : -x.
; Test that the abs library call simplifier works correctly.
; abs(x) -> x >s -1 ? x : -x.
define i32 @test_simplify1(i32 %x) {
; CHECK-LABEL: @test_simplify1(
define i32 @test_abs(i32 %x) {
; CHECK-LABEL: @test_abs(
; CHECK-NEXT: [[ISPOS:%.*]] = icmp sgt i32 %x, -1
; CHECK-NEXT: [[NEG:%.*]] = sub i32 0, %x
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[ISPOS]], i32 %x, i32 [[NEG]]
; CHECK-NEXT: ret i32 [[TMP1]]
;
%ret = call i32 @abs(i32 %x)
; CHECK-NEXT: [[ISPOS:%[a-z0-9]+]] = icmp sgt i32 %x, -1
; CHECK-NEXT: [[NEG:%[a-z0-9]+]] = sub i32 0, %x
; CHECK-NEXT: [[RET:%[a-z0-9]+]] = select i1 [[ISPOS]], i32 %x, i32 [[NEG]]
ret i32 %ret
; CHECK-NEXT: ret i32 [[RET]]
}
define i64 @test_simplify2(i64 %x) {
; CHECK-LABEL: @test_simplify2(
define i64 @test_labs(i64 %x) {
; CHECK-LABEL: @test_labs(
; CHECK-NEXT: [[ISPOS:%.*]] = icmp sgt i64 %x, -1
; CHECK-NEXT: [[NEG:%.*]] = sub i64 0, %x
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[ISPOS]], i64 %x, i64 [[NEG]]
; CHECK-NEXT: ret i64 [[TMP1]]
;
%ret = call i64 @labs(i64 %x)
; CHECK-NEXT: [[ISPOS:%[a-z0-9]+]] = icmp sgt i64 %x, -1
; CHECK-NEXT: [[NEG:%[a-z0-9]+]] = sub i64 0, %x
; CHECK-NEXT: [[RET:%[a-z0-9]+]] = select i1 [[ISPOS]], i64 %x, i64 [[NEG]]
ret i64 %ret
; CHECK-NEXT: ret i64 [[RET]]
}
define i64 @test_simplify3(i64 %x) {
; CHECK-LABEL: @test_simplify3(
define i64 @test_llabs(i64 %x) {
; CHECK-LABEL: @test_llabs(
; CHECK-NEXT: [[ISPOS:%.*]] = icmp sgt i64 %x, -1
; CHECK-NEXT: [[NEG:%.*]] = sub i64 0, %x
; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[ISPOS]], i64 %x, i64 [[NEG]]
; CHECK-NEXT: ret i64 [[TMP1]]
;
%ret = call i64 @llabs(i64 %x)
; CHECK-NEXT: [[ISPOS:%[a-z0-9]+]] = icmp sgt i64 %x, -1
; CHECK-NEXT: [[NEG:%[a-z0-9]+]] = sub i64 0, %x
; CHECK-NEXT: [[RET:%[a-z0-9]+]] = select i1 [[ISPOS]], i64 %x, i64 [[NEG]]
ret i64 %ret
; CHECK-NEXT: ret i64 [[RET]]
}
; The following 5 tests use a shift+add+xor to implement abs():
; B = ashr i8 A, 7 -- smear the sign bit.
; xor (add A, B), B -- add -1 and flip bits if negative
define i8 @shifty_abs_commute0(i8 %x) {
; CHECK-LABEL: @shifty_abs_commute0(
; CHECK-NEXT: [[SIGNBIT:%.*]] = ashr i8 %x, 7
; CHECK-NEXT: [[ADD:%.*]] = add i8 [[SIGNBIT]], %x
; CHECK-NEXT: [[ABS:%.*]] = xor i8 [[ADD]], [[SIGNBIT]]
; CHECK-NEXT: ret i8 [[ABS]]
;
%signbit = ashr i8 %x, 7
%add = add i8 %signbit, %x
%abs = xor i8 %add, %signbit
ret i8 %abs
}
define <2 x i8> @shifty_abs_commute1(<2 x i8> %x) {
; CHECK-LABEL: @shifty_abs_commute1(
; CHECK-NEXT: [[SIGNBIT:%.*]] = ashr <2 x i8> %x, <i8 7, i8 7>
; CHECK-NEXT: [[ADD:%.*]] = add <2 x i8> [[SIGNBIT]], %x
; CHECK-NEXT: [[ABS:%.*]] = xor <2 x i8> [[SIGNBIT]], [[ADD]]
; CHECK-NEXT: ret <2 x i8> [[ABS]]
;
%signbit = ashr <2 x i8> %x, <i8 7, i8 7>
%add = add <2 x i8> %signbit, %x
%abs = xor <2 x i8> %signbit, %add
ret <2 x i8> %abs
}
define <2 x i8> @shifty_abs_commute2(<2 x i8> %x) {
; CHECK-LABEL: @shifty_abs_commute2(
; CHECK-NEXT: [[Y:%.*]] = mul <2 x i8> %x, <i8 3, i8 3>
; CHECK-NEXT: [[SIGNBIT:%.*]] = ashr <2 x i8> [[Y]], <i8 7, i8 7>
; CHECK-NEXT: [[ADD:%.*]] = add <2 x i8> [[Y]], [[SIGNBIT]]
; CHECK-NEXT: [[ABS:%.*]] = xor <2 x i8> [[SIGNBIT]], [[ADD]]
; CHECK-NEXT: ret <2 x i8> [[ABS]]
;
%y = mul <2 x i8> %x, <i8 3, i8 3> ; extra op to thwart complexity-based canonicalization
%signbit = ashr <2 x i8> %y, <i8 7, i8 7>
%add = add <2 x i8> %y, %signbit
%abs = xor <2 x i8> %signbit, %add
ret <2 x i8> %abs
}
define i8 @shifty_abs_commute3(i8 %x) {
; CHECK-LABEL: @shifty_abs_commute3(
; CHECK-NEXT: [[Y:%.*]] = mul i8 %x, 3
; CHECK-NEXT: [[SIGNBIT:%.*]] = ashr i8 [[Y]], 7
; CHECK-NEXT: [[ADD:%.*]] = add i8 [[Y]], [[SIGNBIT]]
; CHECK-NEXT: [[ABS:%.*]] = xor i8 [[ADD]], [[SIGNBIT]]
; CHECK-NEXT: ret i8 [[ABS]]
;
%y = mul i8 %x, 3 ; extra op to thwart complexity-based canonicalization
%signbit = ashr i8 %y, 7
%add = add i8 %y, %signbit
%abs = xor i8 %add, %signbit
ret i8 %abs
}
; Negative test - don't transform if it would increase instruction count.
declare void @extra_use(i8)
define i8 @shifty_abs_too_many_uses(i8 %x) {
; CHECK-LABEL: @shifty_abs_too_many_uses(
; CHECK-NEXT: [[SIGNBIT:%.*]] = ashr i8 %x, 7
; CHECK-NEXT: [[ADD:%.*]] = add i8 [[SIGNBIT]], %x
; CHECK-NEXT: [[ABS:%.*]] = xor i8 [[ADD]], [[SIGNBIT]]
; CHECK-NEXT: call void @extra_use(i8 [[SIGNBIT]])
; CHECK-NEXT: ret i8 [[ABS]]
;
%signbit = ashr i8 %x, 7
%add = add i8 %x, %signbit
%abs = xor i8 %add, %signbit
call void @extra_use(i8 %signbit)
ret i8 %abs
}