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clang-p2996/llvm/test/Transforms/LoopUnroll/full-unroll-keep-first-exit.ll
Philip Reames de2fed6152 [unroll] Keep unrolled iterations with initial iteration 
The unrolling code was previously inserting new cloned blocks at the end of the function.  The result of this with typical loop structures is that the new iterations are placed far from the initial iteration.

With unrolling, the general assumption is that the a) the loop is reasonable hot, and b) the first Count-1 copies of the loop are rarely (if ever) loop exiting.  As such, placing Count-1 copies out of line is a fairly poor code placement choice.  We'd much rather fall through into the hot (non-exiting) path.  For code with branch profiles, later layout would fix this, but this may have a positive impact on non-PGO compiled code.

However, the real motivation for this change isn't performance.  Its readability and human understanding.  Having to jump around long distances in an IR file to trace an unrolled loop structure is error prone and tedious.
2021-11-12 11:40:50 -08:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -loop-unroll < %s | FileCheck %s
; RUN: opt -S -passes='require<opt-remark-emit>,loop(loop-unroll-full)' < %s | FileCheck %s
; Unroll twice, with first loop exit kept
define void @s32_max1(i32 %n, i32* %p) {
;
; CHECK-LABEL: @s32_max1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[N:%.*]], 1
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[N]]
; CHECK-NEXT: store i32 [[N]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC:%.*]] = add i32 [[N]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[N]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_BODY_1:%.*]], label [[DO_END:%.*]]
; CHECK: do.body.1:
; CHECK-NEXT: [[ARRAYIDX_1:%.*]] = getelementptr i32, i32* [[P]], i32 [[INC]]
; CHECK-NEXT: store i32 [[INC]], i32* [[ARRAYIDX_1]], align 4
; CHECK-NEXT: br label [[DO_END]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %n, 1
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %do.body ]
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp = icmp slt i32 %i.0, %add
br i1 %cmp, label %do.body, label %do.end ; taken either 0 or 1 times
do.end:
ret void
}
; Unroll thrice, with first loop exit kept
define void @s32_max2(i32 %n, i32* %p) {
;
; CHECK-LABEL: @s32_max2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[N:%.*]], 2
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[N]]
; CHECK-NEXT: store i32 [[N]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC:%.*]] = add i32 [[N]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[N]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_BODY_1:%.*]], label [[DO_END:%.*]]
; CHECK: do.body.1:
; CHECK-NEXT: [[ARRAYIDX_1:%.*]] = getelementptr i32, i32* [[P]], i32 [[INC]]
; CHECK-NEXT: store i32 [[INC]], i32* [[ARRAYIDX_1]], align 4
; CHECK-NEXT: [[INC_1:%.*]] = add i32 [[INC]], 1
; CHECK-NEXT: [[ARRAYIDX_2:%.*]] = getelementptr i32, i32* [[P]], i32 [[INC_1]]
; CHECK-NEXT: store i32 [[INC_1]], i32* [[ARRAYIDX_2]], align 4
; CHECK-NEXT: br label [[DO_END]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %n, 2
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %do.body ]
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp = icmp slt i32 %i.0, %add
br i1 %cmp, label %do.body, label %do.end ; taken either 0 or 2 times
do.end:
ret void
}
; Should not be unrolled
define void @s32_maxx(i32 %n, i32 %x, i32* %p) {
;
; CHECK-LABEL: @s32_maxx(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[X:%.*]], [[N:%.*]]
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[I_0:%.*]] = phi i32 [ [[N]], [[ENTRY:%.*]] ], [ [[INC:%.*]], [[DO_BODY]] ]
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[I_0]]
; CHECK-NEXT: store i32 [[I_0]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC]] = add i32 [[I_0]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp slt i32 [[I_0]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_BODY]], label [[DO_END:%.*]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %x, %n
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %do.body ]
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp = icmp slt i32 %i.0, %add
br i1 %cmp, label %do.body, label %do.end ; taken either 0 or x times
do.end:
ret void
}
; Should not be unrolled
define void @s32_max2_unpredictable_exit(i32 %n, i32 %x, i32* %p) {
;
; CHECK-LABEL: @s32_max2_unpredictable_exit(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[N:%.*]], 2
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[I_0:%.*]] = phi i32 [ [[N]], [[ENTRY:%.*]] ], [ [[INC:%.*]], [[IF_END:%.*]] ]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[I_0]], [[X:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_END:%.*]], label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[I_0]]
; CHECK-NEXT: store i32 [[I_0]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC]] = add i32 [[I_0]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp slt i32 [[I_0]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP1]], label [[DO_BODY]], label [[DO_END]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %n, 2
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %if.end ]
%cmp = icmp eq i32 %i.0, %x
br i1 %cmp, label %do.end, label %if.end ; unpredictable
if.end:
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp1 = icmp slt i32 %i.0, %add
br i1 %cmp1, label %do.body, label %do.end ; taken either 0 or 2 times
do.end:
ret void
}
; Unroll twice, with first loop exit kept
define void @u32_max1(i32 %n, i32* %p) {
;
; CHECK-LABEL: @u32_max1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[N:%.*]], 1
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[N]]
; CHECK-NEXT: store i32 [[N]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC:%.*]] = add i32 [[N]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[N]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_BODY_1:%.*]], label [[DO_END:%.*]]
; CHECK: do.body.1:
; CHECK-NEXT: [[ARRAYIDX_1:%.*]] = getelementptr i32, i32* [[P]], i32 [[INC]]
; CHECK-NEXT: store i32 [[INC]], i32* [[ARRAYIDX_1]], align 4
; CHECK-NEXT: br label [[DO_END]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %n, 1
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %do.body ]
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp = icmp ult i32 %i.0, %add
br i1 %cmp, label %do.body, label %do.end ; taken either 0 or 1 times
do.end:
ret void
}
; Unroll thrice, with first loop exit kept
define void @u32_max2(i32 %n, i32* %p) {
;
; CHECK-LABEL: @u32_max2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[N:%.*]], 2
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[N]]
; CHECK-NEXT: store i32 [[N]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC:%.*]] = add i32 [[N]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[N]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_BODY_1:%.*]], label [[DO_END:%.*]]
; CHECK: do.body.1:
; CHECK-NEXT: [[ARRAYIDX_1:%.*]] = getelementptr i32, i32* [[P]], i32 [[INC]]
; CHECK-NEXT: store i32 [[INC]], i32* [[ARRAYIDX_1]], align 4
; CHECK-NEXT: [[INC_1:%.*]] = add i32 [[INC]], 1
; CHECK-NEXT: [[ARRAYIDX_2:%.*]] = getelementptr i32, i32* [[P]], i32 [[INC_1]]
; CHECK-NEXT: store i32 [[INC_1]], i32* [[ARRAYIDX_2]], align 4
; CHECK-NEXT: br label [[DO_END]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %n, 2
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %do.body ]
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp = icmp ult i32 %i.0, %add
br i1 %cmp, label %do.body, label %do.end ; taken either 0 or 2 times
do.end:
ret void
}
; Should not be unrolled
define void @u32_maxx(i32 %n, i32 %x, i32* %p) {
;
; CHECK-LABEL: @u32_maxx(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[X:%.*]], [[N:%.*]]
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[I_0:%.*]] = phi i32 [ [[N]], [[ENTRY:%.*]] ], [ [[INC:%.*]], [[DO_BODY]] ]
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[I_0]]
; CHECK-NEXT: store i32 [[I_0]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC]] = add i32 [[I_0]], 1
; CHECK-NEXT: [[CMP:%.*]] = icmp ult i32 [[I_0]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_BODY]], label [[DO_END:%.*]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %x, %n
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %do.body ]
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp = icmp ult i32 %i.0, %add
br i1 %cmp, label %do.body, label %do.end ; taken either 0 or x times
do.end:
ret void
}
; Should not be unrolled
define void @u32_max2_unpredictable_exit(i32 %n, i32 %x, i32* %p) {
;
; CHECK-LABEL: @u32_max2_unpredictable_exit(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ADD:%.*]] = add i32 [[N:%.*]], 2
; CHECK-NEXT: br label [[DO_BODY:%.*]]
; CHECK: do.body:
; CHECK-NEXT: [[I_0:%.*]] = phi i32 [ [[N]], [[ENTRY:%.*]] ], [ [[INC:%.*]], [[IF_END:%.*]] ]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[I_0]], [[X:%.*]]
; CHECK-NEXT: br i1 [[CMP]], label [[DO_END:%.*]], label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr i32, i32* [[P:%.*]], i32 [[I_0]]
; CHECK-NEXT: store i32 [[I_0]], i32* [[ARRAYIDX]], align 4
; CHECK-NEXT: [[INC]] = add i32 [[I_0]], 1
; CHECK-NEXT: [[CMP1:%.*]] = icmp ult i32 [[I_0]], [[ADD]]
; CHECK-NEXT: br i1 [[CMP1]], label [[DO_BODY]], label [[DO_END]]
; CHECK: do.end:
; CHECK-NEXT: ret void
;
entry:
%add = add i32 %n, 2
br label %do.body
do.body:
%i.0 = phi i32 [ %n, %entry ], [ %inc, %if.end ]
%cmp = icmp eq i32 %i.0, %x
br i1 %cmp, label %do.end, label %if.end ; unpredictable
if.end:
%arrayidx = getelementptr i32, i32* %p, i32 %i.0
store i32 %i.0, i32* %arrayidx, align 4
%inc = add i32 %i.0, 1
%cmp1 = icmp ult i32 %i.0, %add
br i1 %cmp1, label %do.body, label %do.end ; taken either 0 or 2 times
do.end:
ret void
}
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