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[SimplifyCFG] Add "safe abs" test from CMSIS DSP 'abs_with_clamp()' 

With -phi-node-folding-threshold=3
this branch would get flattened into select.

See https://reviews.llvm.org/D65148#1629010

llvm-svn: 368847
This commit is contained in:
Roman Lebedev 2019-08-14 13:10:59 +00:00
parent e220c67b7a
commit 4894eeecc9
1 changed files with 34 additions and 0 deletions
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34
llvm/test/Transforms/SimplifyCFG/safe-abs.ll Normal file
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -simplifycfg -S | FileCheck %s
; Reduced from arm_abs_q31() from CMSIS DSP suite.
; https://reviews.llvm.org/D65148#1629010
define i32 @abs_with_clamp(i32 %arg) {
; CHECK-LABEL: @abs_with_clamp(
; CHECK-NEXT: begin:
; CHECK-NEXT: [[IS_POSITIVE:%.*]] = icmp sgt i32 [[ARG:%.*]], 0
; CHECK-NEXT: br i1 [[IS_POSITIVE]], label [[END:%.*]], label [[NEGATIVE:%.*]]
; CHECK: negative:
; CHECK-NEXT: [[IS_INT_MIN:%.*]] = icmp eq i32 [[ARG]], -2147483648
; CHECK-NEXT: [[NEGATED:%.*]] = sub nsw i32 0, [[ARG]]
; CHECK-NEXT: [[ABS:%.*]] = select i1 [[IS_INT_MIN]], i32 2147483647, i32 [[NEGATED]]
; CHECK-NEXT: br label [[END]]
; CHECK: end:
; CHECK-NEXT: [[TMP6:%.*]] = phi i32 [ [[ARG]], [[BEGIN:%.*]] ], [ [[ABS]], [[NEGATIVE]] ]
; CHECK-NEXT: ret i32 [[TMP6]]
;
begin:
%is_positive = icmp sgt i32 %arg, 0
br i1 %is_positive, label %end, label %negative
negative: ; preds = %begin
%is_int_min = icmp eq i32 %arg, -2147483648
%negated = sub nsw i32 0, %arg
%abs = select i1 %is_int_min, i32 2147483647, i32 %negated
br label %end
end: ; preds = %negative, %begin
%tmp6 = phi i32 [ %arg, %begin ], [ %abs, %negative ]
ret i32 %tmp6
}